NEET Biology Class 9 Why Do We Fall Ill Question And Answers

Chapter 4 Why Do We Fall Ill Introduction

In our lower classes, we have observed that cells are the fundamental units of living organisms. They are made of a variety of chemical substances such as proteins, carbohydrates, fats or lipids and so on. We have also seen that each living cell is a dynamic place.

Things are always happening there. For instance, cells move from place to place. Even if a cell is not moving, in it repairing may go on. New cells are being made. In our body organs, too, various specialised activities are going on, e.g., the heart is beating to pump blood to all body parts, the lungs are breathing to exchange gases, the kidneys are filtering the blood and making the urine and brain is thinking.

All these activities of various body organs are interconnected. If kidneys, for example, stop filtering the blood, poisonous substances will accumulate in the body. Under such conditions, the brain will not be able to think properly. For all these interconnected activities, energy and raw materials are needed from outside the body. In other words, food is necessary for cell and tissue functions.

Anything that prevents proper functioning of the cells and tissues will lead to a lack of proper activities of the body.

Chapter 4 Why Do We Fall Ill Health and its Failure

• Significance of Health
  • Health has been described as the state of complete physical, mental and social well being.
  • For keeping a healthy life cycle, a person needs to have a balanced and varied diet, has to take exercise, lives in a proper shelter and takes enough sleep.
  • In addition, good hygiene tend to reduce the chances of infection.
  • A disease is usually due to malfunction of the body.
  • A doctor is able to diagnose what a disease is by looking at the symptoms. Symptoms of a disease may be physical, mental or both.
  • Our health is affected not only by unbalanced diet but also by diseases, which may be water-borne, air­borne or food­borne.
  • Some diseases are caused by infection through microorganisms, insects and parasites.
  • Infection develops when germs/microbes (i.e., viruses) or some-pathogenic (disease-producing) organisms such as bacteria, fungi, protozoans, helminthes, nematodes, etc., enter human body.
  • Personal hygiene and community hygiene help in the prevention and spreading of the causes of diseases.
  • Diseases of humans are due to their wrong food habits. Large families, overcrowded houses and poverty also result in poor health.
• Overlap of Personal and Community Issues for Health
  • Our social environment therefore is an important factor in our individual health.
  • If there are heaps of garbage and trash is littered here and there, or if there is open drain water lying stagnant around where we live, the possibility of poor health increases.
  • Public cleanliness is also important for individual health.
  • Differences between Healthy and Disease free

• • Good economic conditions are also required for good health.
  • We require to be happy in order to be truly healthy.
  • Social equality and harmonious relationships among our population are necessary for the individual health.
  • Thus, we see that there is a overlap of personal and community issues for health.
• Essential conditions for good health
  • Steps to ensure sanitation, i.e., clean surroundings by providing good sewage and rain water disposal systems and proper garbage disposals.
  • Availability of clean drinking water.
  • Availability of adequate, nutritious food.
  • Social equality and harmony.

Chapter 4 Why Do We Fall Ill Disease and its causes

• Human health is negatively affected due to physiological malfunctioning, psychological reasons or pathogenic (disease-causing) organisms.
• Sickness, illness, ailment or disease is a disorder that affects an organism.
• Disease can be defined as an impairment (malfunctioning) of the normal state of the living organism that disturbs or modifies the performance of the vital functions and is a response to environmental factors (as malnutrition, industrial hazards or climate), to specific infective agents (as worms, protozoans, fungi, bacteria or viruses), to inherent defects of the organism (as genetic anomalies) or to combination of these factors.

Sources Of Disease

Human health is effected by various factors, causes or sources These factors are of following types:

• Intrinsic or Internal Factors
  • The disease causing factors which exist within the human body are called intrinsic factors.
  • The important intrinsic factors which affect human health are the following :
    • Malfunctioning or improper functioning of various body parts such as heart, kidney, liver, etc.;
    • Genetic disorder
    • Hormonal imbalances
    • Malfunctioning of immune system of body, e.g., allergy.

• • The diseases caused by intrinsic sources are called organic or metabolic diseases.
  • Some of the diseases caused by intrinsic sources or factors are :
    • Cardiac failure (Heart attack);
    • Kidney failure;
    • Osteoporosis;
    • Myopia;
    • Cataract;
    • Sickle cell anaemia;
    • Haemophilia;
    • Dwarfism;
    • Gigantism;
    • Cretinism;
    • Diabetes;
    • Allergies (e.g.,asthma);
    • Arthritis;
    • Cancer.
  • Classification of some common human diseases

• Extrinsic or External Factors
  The disease causing (pathogenic) factors which enter the human body from outside are called extrinsic factors. The important extrinsic factors which upset human health are the following :
  • Unbalanced diet or inadequate diet.
  • Disease causing microorganisms such as viruses, bacteria, fungi, protozoans, helminthes, worms, etc.;
  • Environmental pollutants;
  • Tobacco, alcohol and narcotic drugs.
• Some of the important diseases caused by extrinsic factors are :
  • Kwashiorkar;
  • Marasmus;
  • Obesity;
  • Night-blindness;
  • Beri-beri;
  • Pellagra;
  • Scurvy;
  • Anaemia;
  • Goitre;
  • Rickets;
  • Fluorosis;
  • Food poisoning;
  • Diarrhoea;
  • Malaria;
  • AIDS;
  • Influenza;
  • Cholera;
  • Measles;
  • Chickenpox;
  • Tuberculosis;
  • Pneumonia;
  • Tetanus;
  • Leprosy;
  • Poliomyelitis;
  • Conjunctivitis;
  • Rabies;
  • Dengu;
  • Hepatitis (Jaundice);
  • Kala-azar ;
  • Amoebic dysentary;
  • Giardiasis; and
  • Skin disease (Ring worm).

Disease-causing microorganisms or pathogens.

• The pathogens include viruses, bacteria, fungi, protozoans, helminths and worms, etc.
• These pathogens are transferred to the human body through air, contaminated water, food, soil, physical contact, sexual contact and animals.

Inadequate diet.

• Absence of nutritional diet makes a person unhealthy.
• Unhealthy persons are more susceptible to diseases or infections.
• Deficiency of nutrients in the diet results in number of deficiency diseases in human beings, e.g., night-blindness, beriberi, scurvy, pellagra, rickets, anaemia, goitre, rickets, osteomalacia, bleeding disease, marasmus, kwashiorkor, etc. . Unbalanced diet may cause obesity.

Environment pollutants. Various environmental pollutants such as gases (e.g., oxides of carbon, oxides of nitrogen and oxides of sulphur), particulate matter, industrial chemicals, heavy metals, (e.g., mercury, lead, cadmium and arsenic), pesticides, etc., also are causes of diseases.

Tobacco, alcohol and narcotic drugs. Continuous use of tobacco, alcohol and narcotic drugs result in harmful effects leading to chronic diseases.

• Levels of Immediate Causes
  • If few babies are suffering from loose motions, we can say that the immediate cause of infection or disease is a virus. Such immediate causes of diseases are called first-level causes.
  • Lack of good nourishment becomes second level cause of the disease the babies suffering from. These babies are not properly fed because they belong to poor house hold.
  • Poor public services providing unclean drinking water in the region where such babies are living in society, and poverty becomes the third level cause of the disease.
  • Possibly, some genetic difference in these few babies might be the reason that makes them more likely to suffer from loose motions when exposed to unclean water containing such a virus. Genetic difference or poor nourishment are contributory causes of the diseases. Contributory causes themselves do not lead to a disease.

Chapter 4 Why Do We Fall Ill Worksheet 1

Question 1. Statement – 1: Personal hygiene and community hygiene help in the prevention and spreading of the causes of diseases.
Statement – 2: Social equality and harmonious relationships are not necessary for the individual health.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 1. Statement – I is true, Statement – 2 is false.

Question 2. Spot the errors in the given statements and correct them.

1. Disease free is a state of complete physical, mental and social well being.
2. Healthy is a state of absence of discomfort or derangement in any part of body.

Answer. Both statements are incorrect.

Question 3. Which of the following are the essential conditions for good health.

1. Availability of clean drinking water.
2. Availability of adequate, nutritious food.
3. Social equality and harmony.
4. All the above

Answer. 4. All the above

Question 4. Statement – 1: The disease causing factors which exist within the human body are called extrinsic factors.
Statement – 2: The disease causing (pathogenic) factors which enter the human body from outside are called intrinsic factors.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 4. Both statements are false.

Question 5. Match the following:

A Graves disease     P Hypo secretion of Aldosterone
B Cretinism             Q Hyper secretion of thyroid hormone
C Myxoderma         R Hypo secretion of Insulin
D Addison’s disease
E Diabetes millitus

Answer. A, B, C – Q ; D – P; E – R

Question 6. Match the following:

Type of disease     Example
A Physical             P Typhoid
B Infectious          Q Haemophilia
C Deficiency         R Bone fracture
D Inherited           S Kwashiorkor

Answer. ABCD/RPSQ

Question 7. Match the following:

Type of disease       Example
A Inherited              P Alcoholism
B Degnerative         Q Paronia
C Mental                 R Arthritis
D Social                   S Sickle Cell anaemia

Answer. ABCD/SRQP

Question 8. Match the following:

Type of disease        Cause
A Infectious             P Inadequate diet
B Deficiency            Q Organs and tissues wear away and do not work so well with age.
C Inherited             R Invasion of the body by other organisms
D Degenerative     S Defective genes passed on from parents to off spring.

Answer. ABCD/RPSQ

Question 9. Match the following:

Column –1             Column–2
A Cardiac failure    P Extrinsic
B Marasmus          Q Intrisinic
C Kidney failure
D Night-blindness

Answer. ABCD/QPQP

Question 10. Match the following:

Column –1      Column–2
A Gigantism    P Extrinsic
B Diabetes      Q Intrisinic
C Diarrhoea
D Pneumonia

Answer. ABCD/QQPP

Question 11. Which of the following are intrinsic factors causing diseases?

P) Malfunctioning or improper functioning of various body parts

Q) Unbalanced diet or inadequate diet.

R) Hormonal imbalances

S) Environmental pollutants

1. P, Q
2. Q, R
3. P, R
4. Q, S

Answer. 3. P, R

Question 12. Which of the following are extrinsic factors causing diseases?

P) Malfunctioning or improper functioning of various body parts

Q) Unbalanced diet or inadequate diet.

R) Hormonal imbalances

S) Environmental pollutants

1. P, Q
2. Q, R
3. P, R
4. Q, S

Answer. 4. Q, S

Question 13. Which of the following are organic diseases?

P) Haemophilia

Q) Pneumonia

R) Cancer

S) Amoebic dysentary

1. P, Q
2. Q, R
3. P, R
4. Q, S

Answer. 3. P, R

Question 14. Which of the following are organic diseases?

P) Dwarfism

Q) Tuberculosis

R) Arthritis

S) Conjunctivitis

1. P, Q
2. Q, R
3. P, R
4. Q, S

Answer. 3. P, R

Question 15. Fill in the following blanks.

1) Kala – azar and Cholera are the diseases caused by ________ factors ( extrinsic / intrisinsic)

2) Sickle cell anaemia and Allergies are the diseases caused by ________ factors ( extrinsic / intrisinsic)

Answer. (a) Extrinsic factors, (b) Intrinsic factors

Question 16. Match the following:

Deficiency        nutrient Disease
A Protein          P Cheilosis
B Vitamin A      Q Beri–Beri
C Vitamin B1    R Night blindness
D Vitamin B2   S Kwashiorkor

Answer. ABCD/SRQP

Question 17. Match the following:

Deficiency          nutrient Disease
A Niacin             P Scurvy
B Vitamin B12    Q Pellagra
C Vitamin C       R Rickets
D Vitamin D      S Pernicious anemia

Answer. ABCD/QSPR

Question 18. Statement – 1: Bleeding disease is caused due to the deficiency of fluorine.
Statement – 2: Deficiency of iodine causes goitre

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 2. Statement – 1 is false, Statement – 2 is true.

Question 19. Fill in the following blanks.

1) Microcytic anameia is caused due to deficiency of _________.

2) Xeropthalmia is caused due to deficiency of _________.

Answer. (1) Iron (2) Vitamin A

Question 20. 1) Give five examples of healthy habits.
2) What is the meaning of word “homeostasis” ?

Answer. Conceptual

Chapter 4 Why Do Fall Ill Types of Diseases

• Acute diseases: Diseases such as influenza are described as acute, because their effects come on suddenly and affect the body quickly, e.g., common cold.
• Chronic diseases: Other diseases are more long-term, with the symptoms lasting for months or years. Such diseases are called chronic diseases, e.g., elephantiasis, tuberculosis.

• Congenital diseases.
  • The diseases that are present since birth are called Congenital disease.
  • These are caused due to genetic. abnormality or due to metabolic disorders or malfunctioning of any organ.
  • They are permanent, generally not easily curable and may be inherited to the children.
• Acquired diseases.
  • Acquired diseases can be broadly classified into two types :
    • communicable or infectious diseases;
    • non-communicable or non-infectious diseases.
  • Infectious diseases
    • The diseases that are communicated from diseased person to healthy person they are known as infectious diseases.
    • These diseases are caused by some biological agents or pathogens such asviruses, bacteria, protozoans, helminthes, nematodes and fungi.
    • Infectious diseases can rapidly spread from one person to another by various means such as by physical contact, water, air, food, and insects (vectors).
  • Non-infectious diseases
    • The non­infectious diseases are restricted only to those persons who are suffering from them.
    • These are not spread from infected person to healthy person.
    • Non-infectious diseases may be caused from :
      • The lack of certain essential substances in our diet, e.g., proteins, vitamins, minerals (deficiency diseases);
      • General wearing out or degeneration of tissues as in old age (degenerative diseases);
      • Uncontrolled growth of tissues in any part of body (cancer);
      • Defects in the metabolic reactions (metabolic disorders); and
      • injury and damage to any part of the body by accidents.

Chapter 4 Why Do We Fall Ill Worksheet 2

Question 1. Statement – 1: Non communicable diseases are are caused by attack of pathogen.
Statement – 2: Infectious or Communicable Diseases are caused by factors other than living pathogen.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 4. Both statements are false.

Question 2. Fill in the following blanks.

1. Infectious diseases are brought about by __________factors.
2. Non-Infectious or Non-Communicable Diseases are brought about by __________factors.

Answer. (1) Extrinsic factors (2) Intrinsic factors.

Question 3. Pick the odd one out.

1. Cold, Cholera, Diabetes, Tuberculosis
2. Diabetes, Cholera, Hypertension, Goitre.

Answer. (1) Diabetes (2) Cholera

Question 4. Statement – 1: Influenza is an acute disease.
Statement – 2: Elephantiasis and tuberculosis are chronic diseases.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 3. Both statements are true.

Question 5. Statement – 1: The diseases that are present since birth are called Congenital disease
Statement – 2: These are caused due to genetic abnormality or due to metabolic disorders or malfunctioning of any organ.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 3. Both statements are true.

Question 6. Assertion (A): The diseases are caused by some biological agents or pathogens such as viruses, bacteria, protozoans, helminthes, nematodes and fungi are infectious in nature.
Reason (R): These diseases can be communicated from diseased person to healthy person.

1. A is correct and R is the correct explanation of A.
2. A is correct and R is not the correct explanation of
3. A is correct and R is wrong.
4. A is wrong and R is correct.

Answer. 1. A is correct and R is the correct explanation of A.

Question 7. Which of the following are the causes of infectious disease?

1. The lack of certain essential substances in our diet,
2. General wearing out or degeneration of tissues as in old age
3. Defects in the metabolic reactions
4. All the above

Answer. 4. All the above

Chapter 4 Why Do We Fall Ill Infectious Diseases

• Infection Agents
  • Organisms that can cause disease are called infection agents.
  • It includes viruses, some are bacteria, some are fungi and some are unicellular animals, the protozoans. Some diseases are also caused by multicellular organisms such as different kinds of worms.
  • Common examples of diseases caused by viruses are the common cold, influenza, dengue, fever and AIDS.
  • Diseases like tyhpoid fever, cholera, tuberculosis and anthrax are caused by bacteria.
  • Many common skin infections are caused by different kinds of fungi.
  • Protozoans cause many familiar diseases such as malaria and kala-azar.
  • Worms tend to cause a variety of intestinal infections and elephatiasis.
  • All viruses live inside host cells, whereas bacteria very rarely do.
  • Viruses, bacteria and fungi multiply very quickly, but worms multiply very slowly in comparison.
  • Antibiotics commonly block biochemical pathways important for bacteria
  • Therefore, most broad spectrum antibiotics work against many species of bacteria, rather than simply working against one.
  • Viruses do not use these pathways at all, that is why antibiotics do not work against viral infection. For example, if we have a common cold, taking of antibiotics does not reduce the severity or duration of disease. Instead our body secrete an antiviral protein, celled interferon to combat the virus of cold.
  • If we get a bacterial infection along with the viral cold, then taking antibiotics will help. In that case, too, the antibiotic will work against the bacterial part of infection, not the viral infection.

Common human disease caused by infectious agents.

• Viruses
  • Common cold
  • Influenza
  • Dengue fever
  • Poliomyelitis
  • Hepatitis –B
  • AIDS (Acquire Immuno Deficiency Syndrome)
  • Chicken pox
  • Measles
  • Mumps
  • SARS (= Severe Acute Respiratory Syndrome)
  • Small pox
  • Swine flu (HINI)
• Bacteria
  • Typhoid fever
  • Cholera
  • Tuberculosis
  • Anthrax
  • Acne (Fig)
  • Tetanus
  • Food poisoning
• Fungi
  • Athlete’s foot, Ringworm and many other skin infections
• Protozoa
  • Malaria
  • Kala-azar
  • Amoebic dysentry
  • Sleeping sickness
• Worm
  • Intestinal worm infection
  • Elephantiasis
• Means of Spread of Infectious Diseases
  Infectious diseases spread from one infected person to other normal persons by a variety of method.
  • Air-borne diseases
    • These diseases are caused due microbes that are spread through air
    • This occurs through the little droplets thrown out by an infected person who sneezes or coughs.
    • Someone standing close by can breathe in these droplets, and the microbes get chance to start a new infection
    • Examples: common cold, pneumonia and tuberculosis.
  • Water-borne diseases,
    • The diseases that spread through water are called Water – borne diseases.
    • This occurs if the stool from someone suffering from an infectious gut disease, such as cholera or amoebiasis, gets mixed with the drinking water used by people living nearby.
    • The cholera-infested bacteria will enter new hosts through the weater they drink and cause disease in them.
  • Sexually-transmitted diseases.
    • These diseases are caused by the pathogens that are transmitted by sexual contact from one partner to the other.
    • Sexually transmitted diseases are not spread by casual physical contact.
    • Casual physical contacts include handshakes, hugs, sports such as wrestling or by any of the other ways in which we touch each other socially.
    • Examples: Syphilis and AIDS
  • Formite borne diseases.
    • Articles coming in contact with patients are a source of infection.
    • Examples: Door handles, taps, garments, currency, utensils, crockery, etc.
  • Spread of disease through vectors.
    • Vectors are carrier of a disease or infection.
    • Many animals which live with us may carry diseases.
    • Thus, these animals act as intermediaries or vectors.
    • Mosquitoes (Anopheles) are vector of a disease, called malaria.
    • In many species of mosquitoes, the females need highly nutritious food in the form of blood in order to be able to lay mature eggs.
    • They feed on many warm-blooded animals including us.

Common Human Diseases transmitted by insects

Thus, means of transmission (spread) of infectious diseases may be of two main types:

Direct transmission :

• Contact with infected person (e.g., AIDS).
• Contact with soil (e.g., Tetanus).
• Animal bites (e.g., Rabies).
• Transplacental (e.g., AIDS, German measels and Syphilis).

Indirect transmission:

• Through vectors (e.g., Malaria).
• Through contaminated food and water (e.g., Amoebiasis, Hepatitis, etc.).
• Air transmitted disease (e.g., common cold, T.B., preumonia).
• Formite borne.

Symptoms of Disease

• Point of entry and place of infection of microbe inside human body.
  • If the microbes enter from the air via the nose, they are likely to go to the lungs.
  • This happens in case of bacteria which cause tuberculosis (T.B.) of lungs.
  • If the microbes enter through the mouth, they can stay in the lining of the gut as do typhoid causing bacteria.
  • These microbes, can also go to the liver, like the viruses that cause jaundice (Hepatitis B). However, this pattern is not followed by all microbes.
  • Infection of HIV takes place via the sexual organs but it tends to spread to lymph nodes all over the body.
  • Malaria-causing protozoan enters through a mosquito bite but it first goes to liver cells and then to red blood corpuscles (RBCs).
  • The virus causing Japanese encephalitis, or brain fever, enter through a mosquito bite. But it goes to infect the brain.
• Symptoms and signs.
  • Symptoms are evidences of the presence of diseases.
  • They are in the form of structural and functional changes in the body or body parts.
  • They indicate that there is something wrong in the body.
  • On the basis of symptoms of a disease physicians search for definite clues or signs of the disease.
  • For this, they use certain instruments and even go for laboratory tests (e.g., tests in pathologist’s labs) to pinpoint the cause of the disease.

• • Most of these common effects of a disease depend on the fact that the immune system of the patient’s body becomes activated in response to an infection.
  • An active immune system recruits many cells to the affected tissue to destroy the disease-causing (i.e., pathogenic) microbes. Such a recruitment process is called inflammation.
  • Local effects of an inflammation is shown in the form of swelling and pain. General effect of an inflammation is depicted in the form of fever.
  • Infection of HIV is found to have multiple dimensional effect. In case of HIV infection, the virus goes to immune system and ultimately damages its function.
  • Many symptoms of HIV-AIDS infection are due to the fact that patients body can no longer fight off many minor infections that he faces every day.
  • Minor gut infection can produce major diarrhoea with blood loss. Thus, it is these secondary infections that kill people suffering from the HIV-AIDS.

Principle of Treatment

• There are two ways to treat an infectious disease. One is to reduce the effects of the disease and the other is to kill the cause of the disease. For the first requirement, we can provide treatment that will reduce the symptoms. The symptoms are usually because of inflammation.
• Pathogenic microbes can be killed by two common methods. One way is to use medicines that kill microbes and the other way to affect antibiotics.

Chapter 4 Why Do We Fall Ill Antibiotics

• Antibiotics are chemicals produced by mirco organisms (mainly bacteria and fungi) which at low concentrations have the ability to inhibit or destroy pathogens. The first antibiotic was penicillin, which was developed in the 1940’s in response to the need to treat soldiers in the Second World War. There are now about 50 to 100 commercially available antibiotics.
• Antibiotics are characterised by their range of effectiveness and their mode of action against the pathogens:
  • Broad spectrum antibiotics kill a wide range of bacteria.
  • Narrow spectrum antibiotics are effective against only a few types of bacteria.
    To kill a specific pathogen, you have to use a narrow spectrum antibiotics which is specific for the disease.
• All antibiotics must have selective toxicity. This means they should kill or inhibit the growth of bacteria or fungi, but cause little or no damage to the host.
  Antibiotics tend to interfere with the growth or metabolism of the pathogen in a variety of ways.
  • Penicillin inhibits the enzymes that are involved in the formation of the bacterial cell wall. Bacteria with weak cell walls die due to leakage of the cell contents.
  • Streptomycin binds to bacterial ribosomes, so preventing protein synthesis, including synthesis of the enzymes. The lack of protein affects bacteria metabolism and results in its death. Fortunately, bacterial ribosomes are different from human ones. So streptomycin does not interfere with the synthesis of proteins in the cells of the patient (= host) taking the drug.
  • Tetracyclines also work by interfereing with bacterial ribosomes.
  • Polymixines damage bacterial cell (plasma) membranes even in resting cells (spores). Penicillin. Antibiotics tend to be used against bacterial infections more than the fungal infections. This is because fungal cells work in a similar manner to human cells. As a result, many antifungal agents are highly toxic to humans.

Principles of Prevention of Disease

Following three limitations are normally confronted while treating an infectious disease :

• Once someone has a disease, its body functions are damaged and may never recover completely.
• Treatment of a disease takes time. This means that if someone suffering from a disease, he is like to bedridden for sometime, even if we give him proper treatment.
• The person suffering from an infectious disease can serve as the source from where the infection may spread to other people.
  Visualizing these difficulties, prevention of diseases is far better than their cure. There are following two ways of prevention of diseases, one is general another is specific one.

General ways of prevention of infectious diseases.

Public hygiene is one basic key to the prevention of infectious diseases. Thus, in this method of prevention of diseases, following practices are adopted :

• For air-borne microbes, we can prevent exposure by providing living conditions that are not overcrowded.
• For water-borne microbes, we can prevent exposure by providing safe drinking water.
• For vector-borne infections, we can provide clean environments. Such a clean environment, for example, would not allow mosquito breeding.

Specific ways of prevention of infectious diseases.

Immune system and immunisation: Children escape infection of cold and cough because the immune system of their bodies is normally fighting off the microbes (pathogenic microorganisms). These cells go into action each time infecting microbes enter the body. If these cells are successful.

• The immune cells (WBCs) manage to kill off the infection long before it assumes major proportions.
• Becoming exposed to infection or be infected with an infectious microbe does not necessarily mean developing noticeable disease.
• One way of looking at severe infectious disease is that it represents failure of the immune system. The functioning of the immune system, like any other system in the body, will not be good enough if proper and sufficient nourishment and food is not available.
• Therefore, second basic principle of prevention of infectious disease is the availability of proper and sufficient food for everyone.

Chapter 4 Why Do We Fall Ill Immune Response

• An immune response is the way in which the body responds to invasion by a specific pathogen or antigen.
• This response involves the production of cells (lymphocytes) and chemicals (antibodies) designed to defend the body against the pathogen.
• Antigens are substances that can produce an immune response. Antigens trigger the production of antibodies (glycoproteins or immunoglobulins) by the immune system. Each type of antibodies is specific to a particular antigen and reacts with it to make it harmless.
  • Cell-mediated immunity.
  • Cell-mediated immunity involves T-lymphocytes and macrophages.
  • Macrophages are phagocytic, i.e., they engulf and digest all types of foreign cells and viruses.
  • Lymphocytes are white blood cells that recognise and react with antigens.
  • They are of two types : T- lymphocytes and B-lymphocytes.
  • T-lymphocytes become activated in thymus gland and may be of four types :
    • Cytotoxic T-cells or killer cells
    • Helper T-cells
    • Memory T-cells
    • Suppressor T-cells.
• Antibody-mediated immunity.
  This involves the production of B-lymphocytes which are activated by antigens attached to the macrophage membrane.
  • B-lymphocytes are of three types :
    • Plasma B-cells : They secrete antibodies into the blood circulation.
    • Memory B-cells : They do not produce antibodies, but become programmed to remember a specific antigen and respond very rapidly to any subsequent infection.
    • Dividing B-cells: They produce more B-lymphocyte cells.
• Reaction between antibody and antigen.
  It involves following three steps
  • The antibody becomes attached to the antigen at the antigen-binding site like a key in a lock.
  • This causes the antibody to change from a T-shape to a Y-shape.
  • Antibody cause the antigen to stick together, a process called agglutination which stimulates phagocytosis by neutrophils.
• Active immunity.
  • The pathogen invades the body, which responds by stimulating the production of T-lymphocytes and B-lymphocytes and, both of which are involved in the immune response.
  • Memory cells are formed which provide long-term immunity to the antigen.
  • This type of immunity if termed as active immunity because the lymphocytes are activated by antigens present on the surface of the pathogen. Since this activation takes place during the natural course of an infection, this is called natural active immunity.
  • But the immune response can also be triggered artificially. This involves the injection of antigens into the body. We call this artificial active immunity, although it is more commonly referred to as vaccination.

Passive immunity.

It occurs when an individual becomes temporarily immune to an antigen by receiving ready-made antibodies from someone else. Passive immunity is also of two types :

• Natural passive immunity.
  • It occurs when preformed antibodies pass naturally from mother to baby across the placenta and in breast milk.
  • Immunity is only temporary since the baby’s body does not ‘know’ how to make more antibodies. But it provides the baby with protection until it develops its own immune system.
• Artificial passive immunity.
  • It occurs when pre-formed antibodies extracted from one individual are injected into another as serum.
  • This sort of immunity can provide a “quick-fix” and is given to people who have been bitten by poisonous snakes or rabid dog.

Chapter 4 Why Do We Fall Ill Vaccination

Vaccination is the administration of antigenic material (a vaccine) to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens.

Many such vaccines have infectious diseases, and provide a disease-specific means of prevention. These are vaccines against

1. Tetanus
2. Diphtheria;
3. Whooping cough ;
4. Measles ;
5. Polio;
6. Hepatitis-B;
7. Cholera;
8. Tuberculosis;
9. Plague;
10. Mumps; etc. etc.

All these vaccines form the public health programme of childhood immunisation for preventing infectious diseases.

1. Derivation of term vaccination

Three centuries ago, an English physician Edward Jenner (1749-1823) realised that milkmaids had cowpox did not catch smallpox even during epidemics. He tried deliberately giving cowpox to people, and found that they were now resistant to the smallpox virus.

This was because the smallpox virus is closely related to the cowpox virus. ‘Cow’ is ‘vacca’ in Latin, and a cowpox is ‘vaccinia’. From these roots, the word vaccination has come into our

2. How are vaccines made ?

A vaccine is an antigen that is injected or swallowed. It causes the development of active immunity in the patient. The small quantities of antigen introduced into the person’s body stimulate the production of antibodies as if infected by the disease. This type of immunity is long term since the body is able to produce memory cells in the natural pathway.

Antigens are treated before being introduced to the body of the person, in order to make them relatively harmless. Most vaccines are made in one of the following ways :

• Killed virulent organisms
  • In this case, the bacteria is killed by heat or use by chemicals, which denature its enzymes.
  • So the dead pathogen will not cause the disease, but it will possess antigenic sites on its surface that will be recognised by T- and B- lymphocytes, and result in the production of antibodies in the recipient.
  • There is no chance of the pathogen replicating and causing infection.
  • Example: Vaccine for whooping cough-bacteria.
• Live non-virulent strains
  • Vaccines made in this way are often called attenuated (= weaken) vaccines.
  • In such vaccines, the pathogen is deliberately weakened to ensure that it does not cause severe infection.
  • Examples: Rubella, BCG vaccine used against tuberculosis and the Sabin vaccine used against poliomyelitis, which is taken orally.
• Modified toxins
  • In this type of vaccine, the toxoids (toxic substances) produced by the bacteria are made harmless.
  • Toxoids are used to stimulate antibody production, but there is no risk of infection by the pathogen.
  • Example: Vaccines used against diphtheria and tetanus.
• Isolated antigen
  • Sometime important antigens are separated from the microorganism, in this case by breaking up the pathogen’s structure and obtaining glycoproteins.
  • The “flu vaccine” contains a mixture of antigens from various strains of influenza virus, in an attempt to combat the great variations that exists.
  • This antigenic variation occurs in microorganisms that have a high mutation rate.
  • Example: Influenza.
• Genetically engineered antigens
  • In this most modern type of vaccine, restriction endonuclease enzymes are used to extract from the pathogen the genes that code for a particular antigen.
  • Such genes are inserted in a harmless plasmid vector using a ligase enzyme.
  • The bacterial cells then replicate to produce large amounts of antigen.

Chapter 4 Why Do We Fall Ill Worksheet 3

Question 1. Statement – 1: Infection agents viruses, some are bacteria, some are fungi and some are unicellular animals, the protozoans.
Statement – 2: Infectious diseases are caused only by unicellular organisms.

• Statement – 1 is true, Statement – 2 is false.
• Statement – 1 is false, Statement – 2 is true.
• Both statements are true.
• Both statements are false.

Answer. 1. Statement – 1 is true, Statement – 2 is false.

Question 2. Statement – 1: Common cold, influenza, dengue, fever and AIDS are bacterial diseases.
Statement – 2: Diseases like typhoid fever, cholera, tuberculosis and anthrax are caused by virus.

• Statement – 1 is true, Statement – 2 is false.
• Statement – 1 is false, Statement – 2 is true.
• Both statements are true.
• Both statements are false.

Answer. 1. Statement – 1 is true, Statement – 2 is false.

Question 3. Which of the following statements are false.

P) Malaria and kala-azar are caused by fungi.

Q) Most of the skin diseases are caused by protozoans.

R) Worms tend to cause a variety of intestinal infections and elephatiasis.

S) Antibiotics commonly block biochemical pathways important for bacteria

1. P, Q
2. R, S
3. P, R
4. Q, S

Answer. 1. P, Q

Question 4. Match the following:

Disease                  Caused by
A Dengue fever     P Protozoa
B Typhoid fever    Q Fungi
C Malaria fever     R Bacteria
D Athlete’s foot    S Virus

Answer. ABCD/SRPQ

Question 5. Match the following:

Disease                 Caused by
A Poliomyletis       P Protozoa
B Tuberculosis      Q Fungi
C Ring worm        R Bacteria
D Kala-azar           S Virus

Answer. ABCD/SRQP

Question 6. Spot the errors in the given statements and correct them.

1. Mumps are caused due to bacteria.
2. Measles are caused by protozoans.

Answer. Both are incorrect

Question 7. Fill up the blanks

1. Chicken pox is caused by ( bacteria / virus/ fungi /protozoan)
2. Anthrax is caused by ( bacteria / virus/ fungi /protozoan)
3. SARS is caused by ( bacteria / virus/ fungi /protozoan)
4. Ring worm is caused by ( bacteria / virus/ fungi /protozoan)

Answer. 1) virus

2) bacteria

3) virus

4) fungi

Question 8. Say True or false.

1. Elephantiasis is caused by a worm.
2. Swine flu is a bacterial disease.
3. Tetanu is caused by a virus
4. Amoebic dysentry is a protozoan disease.

Answer. 1) True

2) False

3) False

4) True

Question 9. Match the following:

Disease                   Caused by
A Common Cold     P Vector
B Cholera                Q Sex
C AIDS                    R Air borne
D Malaria                S Water borne

Answer. ABCD/RSQP

Question 10. Assertion (A): Filariasis is a vector transmitted disease.
Reason (R): It is transmitted by a vector named culex mosquito.

1. A is correct and R is the correct explanation of A.
2. A is correct and R is not the correct explanation of
3. A is correct and R is wrong.
4. A is wrong and R is correct.

Answer. 1. A is correct and R is the correct explanation of A.

Question 11. Assertion (A): Syphilis is a sexually transmitted disease.
Reason (R): Epidemic typus is a vector transmitted disease.

1. A is correct and R is the correct explanation of A.
2. A is correct and R is not the correct explanation of
3. A is correct and R is wrong.
4. A is wrong and R is correct.

Answer. 2. A is correct and R is not the correct explanation of

Question 12. Match the following:

Disease                     Caused by
A AIDS                      P Trans placental
B Tetanus                 Q Animal bites
C Rabies                   R Contact with infected person
D German measles   S Contact with soil

Answer. ABCD/RSQP

Question 13. Match the following:

Disease                      Causative agent enters through

A Tuberculosis           P Mosquito bit
B Typhoid                  Q Nose
C AIDS                       R Mouth
D Japanese                S Sexual organs encephalitis

Answer. ABCD/QRSP

Question 14. P indicates the presence of a disease. Q provides the information about the presence of a particular disease. Local effects of an inflammation is shown in the form of R and S. General effect of an inflammation is depicted in the form of T. Identify P, Q, R, S, T.

Answer. P = Symptoms, Q = Signs, R /S=Swelling/Pain, T= Fever

Question 15. Fill up the blanks

1) ___________are chemicals produced by mircro organisms (mainly bacteria and fungi) which at low concentrations have the ability to inhibit or destroy pathogens.

2) __________ antibiotics kill a wide range of bacteria.

Answer. 1) Antibiotics 2) Broad spectrum

Question 16. Match the following:

Column – 1          Column – 2
A Pencillin            P Preventing protein synthesis
B Streptomycin    Q Damage bacterial cell (plasma) membranes
C Tetracyclines     R Interferes with bacterial ribosomes
D Polymixines      S Inhibits the enzymes

Answer. ABCD/SPRQ

Question 17. Which of the following are the limitations that are normally confronted while treating an infectious disease?

1. Once someone has a disease, its body functions are damaged and may never recover completely.
2. Treatment of a disease takes time.
3. The person suffering from an infectious disease can serve as the source from where the infection may spread to other people.
4. All the above

Answer. 4. All the above

Question 18. Match the following:

Disease               Prevention method
A Air borne         P Safe drinking water
B Water borne    Q Clean environments
C Vector borne   R Living conditions that are not overcrowded.

Answer. ABCD/QPR

Question 19. Fill up the blanks

1) An _________is the way in which the body responds to invasion by a specific pathogen or antigen.

2) __________ are substances that can produce an immune response.

Answer. 1) Immune response

2) Antigens

Question 20. Spot the errors in the given statements and correct them.

1. Cell-mediated immunity involves B-lymphocytes
2. Antibody-mediated immunity involves the production of T – lymphocytes and macrophages.

Answer. Both are incorrect.

Question 21. Identify the following type of B– lymphocytes.

P) They produce more B-lymphocyte cells.

Q) They secrete antibodies into the blood circulation.

R) They do not produce antibodies, but become programmed to remember a specific antigen and respond very rapidly to any subsequent infection.

Answer. P) Dividing – B cells

Q) Plasma – B cells

R) Memory – B cells

Question 22. 1) _________occurs when preformed antibodies pass naturally from mother to baby across the placenta and in breast milk. ( Natural passive immunity / Artificial passive immunity)

2) ___________occurs when pre-formed antibodies extracted from one individual are injected into another as serum. ( Natural passive immunity / Artificial passive immunity)

Answer. 1) Natural passive immunity

2) Artificial passive immunity)

Question 23. Statement – 1: A vaccine is an antigen that is generally applied on the skin.
Statement – 2: Vaccine for whooping cough-bacteria is made by killing virulent organisms.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 2. Statement – 1 is false, Statement – 2 is true.

Question 24. Statement – 1: Vaccines made Live non-virulent strains are often called attenuated vaccines.
Statement – 2: The “flu vaccine” contains a mixture of antigens from various strains of influenza virus, in an attempt to combat the great variations that exists.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 3. Both statements are true.

Question 25. Name the vaccines used for the following diseases.

P) Diphtheria

Q) Poliomyelitiss

R) Tuberculosis

S) Heptatitis

T) Heamophilus influenzae type B

Answer. P) DPT-Hib

Q) Polio

R) BCG

S) Hepatitis – B

T) DPT-Hib

Question 26 The age group for different vaccines is mentioned below. Name the vaccine for each of the following.

P) All infants up to 5 years of age; minimum of three doses at one month interval.

Q) All infant, children and even adult.

R) To all infants of l 1/2, 2 1/2 and 3 1/2 month age.

S) All children between 10 to 14 years.

Answer. P) Polio

Q) Hepatitis-B

R) DPT-Hib

S) BCG

Question 27. (1) What do you mean by symptoms of a disease ?

(2) What are signs of disease ?

(3) Give one example of each of diseases caused by bacteria and virus.

Answer. Conceptual

Question 28. (1) Name the causal organism of ringworm and elephantitis.

Answer. Fungi and worm

(2) Name a sexually transmitted disease caused by bacteria.

Answer. Syphilis

(3) What is full form of HIV ?

Answer. Human Immunodeficiency Virus

Question 29. (1) Name the disease transmitted by dog bite.

Answer. Rabies

(2) Name the causal organism of kala-azar.

Answer. Protozoan

(3) Why female Anopheles mosquito feeds on human blood ?

Answer. Conceptual

Question 30. (1) Name two diseases transmitted by the contaminated food and water.

Answer. Typhoid & cholera

(2) Name the causal organism of measles and anthrax respectively.

Answer. Virus & Bacteria

Diseases Caused Due To Infection By Microorganisms

Chapter 4 Why Do We Fall Ill Malaria (caused by protozoan)

• Malaria is a fatal disease of human beings.
• There are about 300 million people around the world which are infected with malaria every year.
• More than 2 millions persons die annually due to malaria disease.
• Malaria is caused by a protozoan parasite Plasmodium.
• This disease spreads through the bite of an insect vector—the female Anopheles mosquito which feeds on human blood.

Symptoms

• Main symptoms of malaria include headache, nausea, muscular pain and high fever.
• Each malarial attack is of 6 to 10 hours duration and consists of the three stages :
  • Cold stage, i.e., feeling very cold and shivering;
  • Hot stage, i.e., high fever, faster respiration and heart beat; and
  • Sweating stage, i.e., due to profuse sweating temperature goes down to normal.

Note:

• Even after the patient is cured of malaria, the patient feels weak and becomes anaemic.
• Malaria may also secondarily cause enlargement of spleen and liver.
• Presence of malarial parasite can be checked by blood test.

Some Facts About Malaria

• The name Malaria was proposed by Macculoch (1827).
• C.L.A. Laveran (1880), a French physician, discovered the Malarial parasite-Plasmodium in the blood of malaria patient. He received Nobel Prize for this discovery in 1907.
• Sir Ronald Ross (1897), a British physician, confirmed that malaria is caused by malarial parasite and mosquito is the vector. He received Nobel Prize for this discovery in 1902.
• Recently Allan Porter and his coworkers produced a genetically engineered aquatic bacteria at National Institute of Singapore. When mosquito larvae feed on these bacteria, they are killed by the toxic substance produced by these bacteria. This can prove to be an effective biological control method.
• Central Drug Research Institute (CDRI), Lucknow has developed an anti-cerebral malarial drug called-Arteether. This drug is extracted from a herbaceous plant Artemisia annua belonging to family Asteraceae.

Prevention

• Malaria is an infectious disease. It spreads from infected person to healthy person (hosts) by the bite of female Anopheles mosquitoes (vectors).
• The only way to prevent malaria is to prevent mosquitoes from biting.
  We can protect us from the bite of mosquitoes by following methods :
• Wire-gauze should be used on doors and windows of our houses to prevent entry of mosquitoes.
• Insect-repellents (e.g., Odomas) should be used to prevent mosquito-bite.
• We should sleep under mosquito net.
• Mosquito larvae should be killed by sprinkling kerosene oil on large-sized water bodies. Some larvivorous fishes such as Gambusia, minnows or trouts or birds (e.g., ducks) can be introduced in water bodies. These animals feed on mosquito larvae and hence larvae get killed and population of mosquitoes is checked. This is called biological control of mosquito.
• Adult mosquitoes can be killed by spraying insecticides (e.g., BHC, malathion) on the walls of human dwellings. Insecticides are chemical poisons (toxicants), hence, regulation of mosquito population by them is called chemical control. Now another insecticide DDT is not used in the chemical control of mosquitoes, since, it persists in the environment for much longer time and cause toxicity by accumulation in the body of fishes, birds and humans through food chains.
• The breeding grounds should be destroyed. Thus, the ditches, puddles or swamps around human dwellings should be drained or filled. We should not allow the collection of water in any uncovered container such as water tank, pot, cooler, flower pot, discarded tyres (tires) etc.

Control

• A drug named quinine, which is extracted from the bark of Cinchona tree, is used to treat a person suffering from malaria.
• This drug kills most of the stages of malarial parasite.
• There are certain other drugs (medicines) which should be taken on the advice of doctor.

Chapter 4 Why Do We Fall Ill Influenza

• Influenza is commonly called flu.
• It is an international disease and is caused by influenza virus (Myxovirus influenza).
• There exist three types of influenza viruses- A, B and C.
• A and B types of influenza viruses are important because these are responsible for epidemics of disease throughout the world.
• The inhaled virus attacks the epithelial cells in the mucous membrane of nose, throat and upper respiratory tract.
• Influenza is spread mainly from person to person contact and by droplet infection via sneezing, coughing or talking.

Symptoms

• The common symptoms of influenza disease are sudden onset of chills, discharge from the nose, sneezing, fever, headache, muscular pains, coughing, inflammation of respiratory mucosa and general weakness. Fever lasts three days in adults.

Prevention

• We should try to keep away from flu patients.

Control

• There is no effective control for influenza. However, vaccines are used for the control of infection and antiviral drugs are used for cure.
• Amantadine and Rimantidine are recommended for the treatment of influenza. Rest speeds up the recovery.

Chapter 4 Why Do We Fall Ill Jaundice or hepatitis

• Jaundice or hepatitis is the disease of liver.
• Since liver is a very important organ in body, so its inflammation due to jaundice affects digestion adversely.
• Jaundice is caused by viral infection.
• The types are : Hepatitis A, Hepatitis B, Hepatitis C, Hepatitis D, Hepatitis E or Hepatitis G.
• Except for type B which is a DNA virus, all the other are RNA viruses.
• Hepatitis is spread mostly by food and water contaminated with hepatitis virus.

Hepatitis A

• Hepatitis A or infectious hepatitis by a RNA-containing virus is an acute infectious disease of liver which affects mainly children and young adults.
• Transmission of hepatitis A virus (HAV) takes place by faecal-oral route, i.e., infection of HAV takes place by ingestion of contaminated water, food or milk.

Symptoms

• High temperature, headache, fatigue, general weakness, and joint pains.
• Loss of appetite (called anorexia) with a feeling of nausea and vomiting.
• Appearance of irritating rashes on body.
• Dark yellow urine.
• Light coloured stool after 3 to 10 days of infection.

Prevention

For avoiding infection of hepatitis A following preventive measures should be taken.

• Use chlorinated, boiled and ozonised water.
• Proper cleaning of hands after handling bed and vessels of the patient.
• Hepatitis-A vaccine should be taken to prevent the disease.

Control

• Application of interferon injection on the advice of the doctor will control the disease.
• For an early cure, it is essential that patient of jaundice should take adequate rest.
• Patient of jaundice should take high calorie diet such as juice of sugarcane, radish with gur (jaggery).
• Consumption of protein and fat should be limited.

Hepatitis B

• Hepatitis B is also known as serum hepatitis or transfusion hepatitis (by a double-stranded DNA virus).
• This is most dangerous and widespread type of viral hepatitis. (Hepatitis B is regarded more dangerous than AIDS).
• It occurs due to infection of Hepatitis B virus (HBV).
• HBV is a blood borne DNA virus.
• The infection of HBV is transmitted by infected blood, inoculation (Inoculation means the introduction of a vaccine into a living being to give immunity), from mothers to their babies and by sexual route (through the semen, saliva, etc.).

Symptoms

• Main symptoms of Hepatitis B include progressive liver disease, chronic active hepatitis and hepatocellular carcinoma (i.e., malignant cancer of liver cells).

Prevention

• Infection of HBV can be prevented by avoiding risky practices such as free or promiscuous sex (Promiscuous means sexual contact which is not restricted to one sexual partner), injectable drug abuse and direct or indirect contact with blood, semen and other body fluids of patients of Hepatitis B.
• Hepatitis B vaccine should be taken to prevent disease.

Chapter 4 Why Do We Fall Ill Rabies (Hydrophobia)

• The bite of a rabid dog (mad dog) and some other rabid mammals such as monkeys, cats or rabbits may cause rabies, which is fatal viral disease caused by a rabies virus or lyssa virus which is present in the saliva of the infected animals.
• The viruses are injected into human blood by the bite of the rabid animal.
• Disease is not expressed after infection even up to 1 to 3 months.
• The long period of incubation makes it possible for a rabies vaccination, after a bite, to develop immunity and prevent the appearance of disease.

Symptoms.

• Rabies is characterised by severe headache, high fever, painful contraction of muscles of throat and chest (due to which there is difficulty in swallowing).
• The patient feels restless, does excessive salivation, has a chocking feeling and finds difficulty in taking in even liquid food. Since patient develops fear of water, the disease is also called hydrophobia.

Prevention

• Cleaning the wound with carbolic soap and clear water immediately after the dog bite is an important preventive measure.
• Any antiseptic medicine (e.g., Savalon, Dettol) should be applied to the wound caused by dog bite. A doctor should be immediately consulted for application of anti-rabies vaccine to the patient.
• Compulsory immunization of stray dogs and cats should be done. Pet dogs should be vaccinated with anti-rabies vaccine.
• A rabid animal shows excessive salivation and tries to seek isolation after bite. Such mad animals should be killed.

Control

• Rabies can be treated with Pasteur’s treatment (discovered by Louis Pasteur), in which a course of 14 vaccines was given.
• Currently 5 anti-rabies vaccines are prescribed at an interval of 0-3-7-14-30 day of dog bite.

Chapter 4 Why Do We Fall Ill AIDS

• AIDS stands for Acquired Immuno Deficiency Syndrome.
• It is a fatal disease.
• The disease of AIDS is caused by retrovirus (a RNA virus) known as Human Immunodeficiency Virus (HIV) AIDS virus attacks white blood cells (WBCs) or lymphocytes (T4 helper cells) of human beings and weakens the human body’s immunity or self- defence mechanism.
• Since AIDS virus reduces the natural immunity of the human body, therefore, the patients suffering from AIDS becomes prone to many other infections or diseases.
• The patients suffering from AIDS die from other infections (called secondary infections).
• Death occurs because the patient’s body cannot resist the attack of pathogens of secondary infections since patient’s natural defence mechanism has been destroyed by AIDS virus.
• Transmission. AIDS disease spreads among human beings by the following ways
• The AIDS disease usually spreads through unprotected (i.e., without the use of condom; condom is a membranous penile sheath of rubber having an anti-veneral or contraceptive function) sexual contact with an infected person carrying AIDS virus. Thus, AIDS is a sexually transmitted viral disease.
• The AIDS disease also spreads through the transfusion of blood contaminated with AIDS virus.
• The AIDS disease also spreads through the use of infected needles for injections (i.e., sharing of infected injection needles which have not been sterilised).
• An AIDS infected mother can transmit the virus to her child during pregnancy or during birth (i.e., by mother’s blood). This is called vertical transmission.

Note:

• AIDS was first detected in USA in 1981 and in India, first confirmed evidence of AIDS infection came in April 1986 from Tamil Nadu.
• The AIDS disease has spread in epidemic form in Africa and western countries. This is because of the undesirable sexual practices, polygamy and polyandry.
• Recently alarmingly increasing cases of AIDS have been reported from different parts of India.

Symptoms.

• Swollen lymph nodes; regular fever; sweating at night and weight loss.
• AIDS virus causes severe damage to brain and may lead to loss of memory, ability to speak and of clear thinking.

Prevention and control.

So far no medicine or vaccine has been developed to cure AIDS, so, once a person gets AIDS, he is sure to die in a short span of time. The following steps may help in controlling infection of this dreaded disease :

• People should be educated about AIDS transmission.
• Disposable syringes and needles should be used for injection.
• Sexual contact with unknown people should be avoided.
• High risk groups should refrain from donating blood.
• Sterilised needles may be provided to drug addicts.
• Before receiving blood for transfusion, one should ensure that it has been screened for HIV.
• The common razor at the barber’s shop should not be used.

Chapter 4 Why Do We Fall Ill Polio

• Poliomyelitis or polio is a disease of the nervous system caused by one of the smallest known virus, called polio virus.
• The virus enters the body through the food and water and reaches the intestine and from there it enters the CNS or central nervous system (brain and spinal cord) via blood stream and lymphatic systems.
• In CNS, the virus destroys the motor nerve cells of spinal cord that are responsible for the muscular control. Therefore, the muscles of polio-infected person become unable to carry out the normal functions.
• Polio is a kind of paralysis and it affects more to the legs.
• Children between the age of 6 months and 3 years are most prone to polio infection.
• Polio is transmitted among children by the faeco-oral route and through the direct contact, dirty hands, contaminated food or milk and flies.
• Faeco-oral route of infection of a disease includes transmission of an infection via food/water that is contaminated by stool of the patient.

Symptoms

• The early symptoms of the polio disease are sore throat and headache.
• If the infection persists, the patient suffers from fever, vomiting, muscular pain, stiffness in the neck, tingling sensation in limbs and ultimately occurrence of paralysis.
• Sooner or later polio results in atrophy of skeletal muscles and deformity of affected limb.

Prevention.

• Complete rest and physiotherapy is helpful in the beginning of attack of polio virus.
• Exercising of legs is done to reduce the paralytic effect.
• Maintenance of hygiene by proper sanitary disposal of waste is an essential step for prevention of polio.
• Oral Polio Vaccine (OPV) is given orally to the children as per National Immunisation Schedule in our country.
• OPV is a live attenuated (diluted or weakend) viral strain taken by mouth and colonises the gut and induces immunity.

Pulse polio immunisation programme (PPIP).

• Pulse polio immunisation programme forms the largest single day public health project.
• Pulse means a dose of a substance (here polio vaccine) especially when applied over a short period of time.
• It was conducted for the first time in December 1995, in an attempt to eradicate polio from our country.
• This programme uses oral polio vaccine or OPV.
• As per the National Immunisation Schedule (NIS), a dose of 3 drops (0.5 ml) is given orally to the child, i.e., one dose each at 1.5, 2.5 and 3.5 month’s age.
• Finally, a booster dose is given at the age of 1.5 years.
• The vaccine consists of milder forms of polio viral particles.
• After oral administration, virus particles in the vaccine begin to live in the intestine of the human body and multiply.
• It leads to production of protective molecules (antibodies) in the intestine and the blood.
• The prefixed days, on which pulse polio immunisation is to be carried out throughout the country, are called National Immunisation Days (NIDS).
• The pulse polio immunization campaign seems to be a successful programme.
• Since the incidence of poliomyelits in Inda has decreased dramatically, India recorded 4,791 cases of polio in 1994; 2,489 in 1997; 1600 in 2002; 225 in 2003 and 135 in 2004 (Renu Verma 2011).
  Aims of Pulse Polio Immunisation Programme (PPIP)
  • To immunise those children who are not earlier immunised or are partially immunised.
  • To replace the disease-causing wild virus by harmless vaccine virus in the environment.

Chapter 4 Why Do We Fall Ill Tuberculosis (T.B.)

• Tuberculosis was first discovered by German scientist Robert Koch in 1882. He was awarded Nobel Prize for this discovery in 1905.
• T.B. is an infectious disease which is communicated from one person to another directly or indirectly.
• Tuberculosis is also contracted from animals (e.g., cattle).
• Tuberculosis is caused by a bacterium-called Mycobacterium tuberculosis. The bacterium releases a toxin called tuberculin.
• T.B. can affect all parts of body such as lungs, lymph glands, bones, intestine, etc.
• In human beings, the infection of T.B. spreads by inhaling infected droplets released through coughing, sneezing, talking and spitting by the patient.
• The incubation period of T.B. includes a few weeks to a few years.

Symptoms.

• The patient of tuberculosis feels sick and weak.
• There is a loss of appetite and weight.
• Typical fever pattern and night sweats are also common.
• The symptoms of T.B. vary depending on the site of the infection (disease) in the body.
• There are following two specific sites of tuberculosis infection.
  • Lung or pulmonary T.B.
    • The person suffered with pulmonary T.B. has continuous fever, persistent cough and produces blood stained sputum.
    • There is loss of weight and weakness.
    • The chest-pain and breathlessness are common features of patients of lung T.B.
    • When the tuberculosis bacteria get into the lungs, they set up a local inflammation and produce an abscess.
    • This usually heals up and leaves a small patch of scar tissue which shows up in X-rays photographs.
    • In advanced stages of tuberculosis large areas of the lungs are destroyed.
  • Lymph gland T.B.
    Symptoms of T.B. of lymph gland include swelling and tenderness of lymph glands, often in the leg which may discharge secretion through the skin.

Prevention.

• Vigorous public health measures are the best method of prevention. Other preventive measures include isolation and proper rehabilitation of the patient. Avoidance of over-crowding, provision of good ventilation and better nutrition help to reduce the incidence of the disease.
• Immunisation with BCG or Bacillus-Calmette-Guerin vaccination prevents tuberculosis. BCG vaccine contains weakened Tuberculosis bacillus and it is injected into the skin of a person to give immunity for 3 to 5 years.

Control.

The tuberculosis can be cured by the following six essential drugs.

• Rifampicin (RMP);
• INH;
• Streptomycin;
• Pyrazinamide;
• Ethambutol; and
• Thioacetozone.

Thus, T.B. can be controlled by the use of antitubercular therapy (ATT)

NOTE:

• The diagnosis of tuberculosis is made on the basis of positive tuberculin test, chest X-rays, positive sputum, gastric analysis, etc
• Tuberculosis is not a hereditary disease.
• The modern treatment of tuberculosis is based on the six main factors : namely rest, diet, drugs, surgery, rehabilitation and health education.
• BCG vaccine is injected into the skin for providing considerable protection against the tuberculosis disease.

Chapter 4 Why Do We Fall Ill Cholera

• Cholera is an acute infectious, fatal disease and is more common during overcrowded fairs, festivals and after floods.
• Sometimes cholera occurs in epidemic form (epidemic means wide and destructive in occurrence) spread over large population.
• Cholera is caused by the bacterium Vibrio cholerae.
• It is transmitted by flies, contaminated water and food.
• When sanitation is poor, it spreads rapidly.
• The incubation period of cholera is generally from a few hours to two or three days.
• When the bacteria of cholera are ingested, they multiply in the small intestine and invade its epithelial cells.
• When the bacteria die, they release toxins which irritate the intestinal lining and lead to the secretion of large amounts of water and salts.

Symptoms

• Watery diarrhoea (i.e., rice-water like stools) which is generally painless.
• Effortless vomiting without nausea.
• Loss of several litres of fluid from patient’s body takes place within hours. This results in dehydration, muscle cramps and weight loss.
• Great loss of mineral salts and body fluid leads to kidney failure.
• Eyes of patient become shrunken.

Prevention

• Persons should be immunised by standard cholera vaccine. One dose of immunisation lasts for about six months.
• In cholera-prone areas, boiled water and cooked food should be taken.
• Careful personal hygiene and good sanitation in the community are the only certain protection against cholera.

Control

• For preventing dehydration therapy with Oral Rehydration Solution(ORS) should be done immediately. ORS solution contains 3.5 g sodium chloride, 2.5 g sodium bicarbonate, 1.5 g potassium chloride, 20 g glucose, 40 g sucrose in one litre water. Taking small sips of ORS solution at intervals prevents dehydration of the patient.
• Immediate medical advice should be taken.
  Antibiotics such as tetracycline kill the bacteria of cholera.

Chapter 4 Why Do We Fall Ill Typhoid

• Typhoid is most common infectious or communicable disease of India.
• Typhoid fever is common in humans of the 1 to 15 years age group.
• Typhoid is caused by a rod-shaped and motile bacterium, called Salmonella typhi which is commonly found in the intestine of human beings. Human infection is direct.
• Infection takes place by the oral route through ingestion of food, milk or water contaminated by contact with faecal matter of the typhoid patient.
• The bacteria spread through faecal matter by house flies.
• The symptoms of typhoid often appear 10 to 14 days after the infection.

Symptoms

• Headache and typhoid fever which rises maximum in the afternoon. The temperature increases each day in the first week.
• High fever in the second week. Fever gradually declines during 3rd and 4th day.
• In nutshell symptoms of typhoid include continuous fever often with delirium (disorder of the mind), slow pulse, tender and distended abdomen, diarrhoea with water-green stools and eruption of rosy spots (rash) on the body of the patient.

Prevention

• Proper sanitation and disposal of faecal matter prevents infection.
• TAB-vaccination provides immunity for 3 years. (TAB vaccine contains killed typhoid bacilli and paratyphoid organisms-Salmonella paratyphi A and B).
• Typhoral oral vaccine also prevents typhoid.

Control

There are standard drugs (e.g., Chloromycetin) which cure typhoid.

Diarrhea

• Diarrhoeal disease form a group of intestinal infections, including food poisoning. The main symptom of all such infections is diarrhoea.
• Diarrhoea is an abnormally frequent discharge of semisolid or fluid faeces.
• Other symptoms of diarrhoeal disease include decreased appetite, nausea, vomiting, borborygmus (i.e., gurgling noise produced by movement of gas in the alimentary canal) and abdominal cramps.
• There may be blood and mucus in the stools.
• Persistent vomiting and loose stools cause dehydration and shock. Blood pressure may fall, pulse rate increases and temperature rise.
• Diarrhoea is one of the major causes of infant mortality in India.
• Infection of diarrhoea spread through contaminated food, water, drinks, hands, clothes, bed sheets and utensils.
• The causative agents of diarrhoea are mainly bacteria such as Escherichia coli, Clostridium botulinum, Shigella dysentiriae, Campylobacter jejuri and Salmonella .
• The protozoans (Entamoeba histolytica, Giardia intestinalis and Balantidium coli), some viruses (Rotavirus, Enterovirus, Adenovirus and Norwalk) and nematodes (Ascaris) also act as causative agents of diarrhoea.

Symptoms

• Frequent loose motions and vomiting lead to dehydration.
• Dehydration (loss of water from body tissues) which makes the patient dangerously ill in a very short time.
• Most of the infant deaths due to diarrhoea can be prevented by making sure that dehydration does not take place due to excessive loss of body fluids through stools and vomiting.
• In cases of dehydration, the patient becomes irritable, eyes appear sunken, nose is pinched and the tongue and the inner side of cheeks appear dry.
• There is sudden weight loss, weak pulse, deep breathing and fever or fits.

Prevention

• Eatables should be covered to prevent their contamination.
• Fruits and vegetables should be properly washed before use.
• Proper personal hygiene is important. Hands should be washed with soap and water before eating any food.
• Stale food should not be consumed.
• Community hygiene is also important.

Control

• Complete bed rest should be ensured till the illness is fully controlled.
• For treating diarrhoea anti-microbial drugs and anti-diarrhoel agents should be used.
• If there is frequent vomiting, liberal amount of fluids with electrolytes should be provided orally.
• Pulp of boiled unripe banana along with required amount of salt, turmeric powder and lime is helpful in controlling the diarrhoea.
• Husk of isabgol seed (Plantago ovata) with water or curd provides relief.
• Saline drip may be given intravenously to maintain fluid and electrolytes in the body. Alternatively oral rehydration solution (ORS) may be given to the patient periodically.
• Dilute soups and dais, rice-water and butter-milk can also be given to the child to compensate the loss of water. Meanwhile, a doctor should be called in who will give some antibiotic treatment. In children, diarrhoea can be prevented by keeping clean surroundings, clean milk and feeding bottles and by following proper feeding habits. There is no vaccine for preventing diarrhoea.

Chapter 4 Why Do We Fall Ill Peptic Ulcers

• Peptic ulcers are painful bleeding areas in stomach and duodenum.
• Robin Warren a Perth based Australian pathologist observed in 1984 that areas of peptic ulcers contained many small curved gram negative bacterium, named Helicobacter pylori
• Barry Marshall , a young clinical fellow of Warren succeeded in culturing the bacteria (1985).
• Marshall and Warren (1985) found that amoxicillin, an antibiotic effective in killing the bacteria could also cure the peptic ulcers.
• The finding helped in changing once painful chronic and disabling condition into short duration treatable disease. For this breakthrough Marshall and Warren were awarded Nobel Prize for Physiology and Medicine in 2005.

Chapter 4 Why Do We Fall Ill Anthrax

• Anthrax is an acute infectious disease caused by a rod-shaped non-motile bacterium called Bacillus anthracis.
• This disease commonly occurs in wild and domesticated animals such as cattle, sheep, goat, horses and pigs.
• Anthrax can spread by eating under-cooked meat of infected animals.
• Human beings can also contract infection from animal products such as bones, wool, hide and bristles. B. anthracis produces an extra-cellular toxin.
• Fowls are resistant to anthrax.

Symptoms.

Infection of anthrax can occur in following three forms:

• Cutaneous (skin);
• Inhalation; and
• Gastrointestinal.
  • Cutaneous anthrax
    About 20 per cent of untreated cases of cutaneous anthrax will result in death. Cutaneous cases are rare.
  • Intestinal anthrax.
    Its symptoms are nausea, loss of appetite, vomiting, pain and vomiting blood. It results in death of 25 per cent to 60 per cent cases.
  • Infection by inhalation.
    Its initial symptoms may resemble a common cold leading to severe breathing problems. It ultimately results in death of patient.

Prevention

• Vaccine of anthrax is found to provide 93 per cent protection against anthrax.
• Course of four subcutaneous injections of anthrax vaccine is recommended. Mild adverse reaction to the vaccine of anthrax is reported.

Control

• Treatment should be started early to get good result. At this stage food infection should be distinguished from food poisoning.
• In food infection, food merely transfers bacteria into the body.
• In food poisoning, bacteria grow in food and release toxins.
• When such a food is taken, toxins are absorbed into the blood from the digestive tract.
• They affect the body quickly, causing gastrointestinal trouble and other effects.

Some Vital Facts About Diseases

• Dengue fever is a viral disease whose vector is Aedes aegypti. It is a daytime biting mosquito.
• World T.B. Day : 24th March.
• National T.B. Control Programme was started in 1962.
• The WHO has announced a new treatment, and management regimen-Directly Observed Treatment, Short-course (DOTS) for the control of tuberculosis (TB), also called “White plague” and for reducing the threat of multi drug resistant strains in the next decade. (Regimen = A systematized course of living, as to food, clothing, etc.).
• The incidence of tetanus in India is about 30 to 50 per one lakh. Neonatal tetanus carries a mortality type of 90 percent.
• Bubonic plague is commonest type of plague. It is caused by a bacterium of the genus Yersinia {Y.pestis).
• Incidence of diarrhoel diseases is highest in Andhra and Orissa states of India.
• Hepatitis B is more dangerous than AIDS.
• Malaria Day. August 20.
• The Integrated Child Development Scheme (ICDS) offers a series of services to control nutritional problems. Health centres distribute tablets of iron and folic acid among women and children to prevent anaemia. Vitamin A is also given to children orally under various schemes.
• WHO (World Health Organisation, 1978) has defined health to be “A state of complete physical, mental and social well being (and not merely the absence of disease or infirmity) that enables one to lead a socially and economically productive life”.
• World AIDS day is December 1.
• Because of weight loss of AIDS patient, this disease is also called slim disease.

Chapter 4 Why Do We Fall Ill Worksheet 4

Question 1. Name the causative agent for the following diseases.

1. Malaria
2. Influenza
3. Hepatitis A
4. Rabies
5. AIDS

Answer. 1) Plasmodium

2) Myxovirus influenza

3) RNA containing virus

4) lyssa virus

5) Human Immunodeficiency Virus (HIV)

Question 2. Name the causative agent for the following diseases.

1. Polio
2. TB
3. Cholera
4. Typhoid
5. Diarrhoea
6. Peptic ulcer

Answer. 1) Polio virus

2) Mycobacterium tuberculosis

3) Vibrio cholerae.

4) Salmonella typhi

5) Escherichia coli, Clostridium botulinum, Shigella dysentiriae, Campylobacter jejuri and Salmonella

6) Helicobacter pylori

Question 3. Vijay’s friend Raj was not attending the classes due to ill health. The tensed Vijay went to Raj’s house and could find he is having following symtoms.

1. feeling very cold and shivering
2. high fever, faster respiration and heart beat
3. Profuse sweating and low temperature. Based on the above symptoms, interpret the disease with Raj is suffering. Also suggest some preventive methods of that disease.

Answer. Malaria

Question 4. Statement – I: Malaria disease spreads through the bite of an insect vector, the female Anopheles mosquito.
Statement – 2: Malaria may also secondarily cause enlargement of spleen and liver.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 3. Both statements are true.

Question 5. Fill up the blanks.

1) A drug named __________, which is extracted from the bark of Cinchona tree, is used to treat a person suffering from malaria.

2) Influenza is caused by _________ virus.

Answer. 1) Quinine

2) Myxovirus influenza

Question 6. Say True or False

1. Influenza is spread mainly from person to person through female anopheles mosquito.
2. Jaundice or hepatitis is the disease of liver.
3. The drug named qunine is recommended for the treatment of influenza.
4. Infection of HAV takes place by ingestion of contaminated water, food or milk.

Answer.

1) False

2) True

3) False

4) True

Question 7. Assume that your friend is ill. If the following symptoms are seen, identify the disease. Sudden onset of chills, discharge from the nose, sneezing, fever, headache, muscular pains, coughing, inflammation of respiratory mucosa and general weakness.

Answer. Influeza

Question 8. Which of the following are the symptoms of Heptatitis A?

P) High temperature, headache, fatigue, general weakness, and joint pains.

Q) Loss of appetite (called anorexia) with a feeling of nausea and vomiting.

R) Dark yellow urine.

S) Painful contraction of muscles of throat and chest

T) The patient feels restless, does excessive salivation, has a chocking feeling and finds difficulty in taking in even liquid food.

Answer. P, Q, R

Question 9. Fill up the blanks.

P) Hepatitis B is also known as ___________or __________.

Q) HBV is a __________virus.

R) Rabies is caused by a ______________which is present in the saliva of the infected animals.

S) Rabies can be treated with __________, in which a course of 14 vaccines was given.

T) AIDS stands for _________________________.

Answer. P) Serum hepatitis or Transfusion hepatitis

Q) Blood borne DNA virus

R) Lyssa virus

S) Pasteur’s treatment

T) Acquired Immuno Deficiency Syndrome.

Question 10. Statement – 1: The disease of AIDS is caused by retrovirus (a DNA virus) known as Human Immunodeficiency Virus (HIV)
Statement – 2:The AIDS disease also spreads through the transfusion of blood contaminated with AIDS virus.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. 3. Both statements are true.

Question 11. Assertion (A): The patients suffering from AIDS becomes prone to many other infections or diseases. Reason (R): AIDS virus reduces the natural immunity of the human body.

1. A is correct and R is the correct explanation of A.
2. A is correct and R is not the correct explanation of
3. A is correct and R is wrong.
4. A is wrong and R is correct.

Answer. 1. A is correct and R is the correct explanation of A.

Question 12. Through which of the following, AIDS is NOT spread through.

P) Unprotected sexual contact with an infected person carrying AIDS virus

Q) Hugging the infected person carrying AIDS virus.

R) Transfusion of blood contaminated with AIDS virus

S) Touching the infected person with AIDS virus.

1. P, Q
2. R, S
3. Q, S
4. P, R

Answer. 3. Q, S

Question 13. Which of the following symptoms are seen in AIDS patient.

P) Swollen lymph nodes

Q) Regular fever

R) Sweating at night and weight loss

S) Damage to brain and may lead to loss of memory

1. P, Q, R
2. Q, R, S
3. P, R, S
4. P, Q, R, S

Answer. 4. P, Q, R, S

Question 14. Assertion (A): The muscles of polio-infected person become unable to carry out the normal functions. Reason (R): The polio virus destroys the motor nerve cells of spinal cord that are responsible for the muscular control.

1. A is correct and R is the correct explanation of A.
2. A is correct and R is not the correct explanation of
3. A is correct and R is wrong.
4. A is wrong and R is correct.

Answer. 1. A is correct and R is the correct explanation of A.

Question 15. Identify the following disease.

Children between the age of 6 months and 3 years are most prone to this disease. The early symptoms of this disease are sore throat and headache. If the infection persists, the patient suffers from fever, vomiting, muscular pain, stiffness in the neck, tingling sensation in limbs and ultimately occurrence of paralysis.

Answer. Polio

Question 16. Write the expanded forms of the following related to diseases.

1) AIDS = Acquired Immuno Deficiency Syndrome.

2) HIV = Human Immunodeficiency Virus

3) HBV = Hepatitis B virus

4) DPT = Diphtheria Pertussis Tetanus

5) BCG = Bacillus-Calmette-Guerin

6) OPV = Oral Polio Vaccine

7) PPIP = Pulse Polio immunisation programme

8)NIDS = National Immunisation Days

9) ATT = Antitubercular therapy

10) ORS = Oral Rehydration Solution

Question 17. Identify the following scientists.

1. The French physician who discovered the Malarial parasite.
2. The British physician who confirmed that malaria is caused by malarial parasite and mosquito is the vector.
3. The German scientist who discovered Tuberculosis.
4. A Perth based Australian pathologist who observed that areas of peptic ulcers contained many small curved gram negative bacterium, named Helicobacter pylori.

Answer. 1) C.L.A. Laveran (1880)

2) Sir Ronald Ross

3) Robert Koch

4) Robin Warren

Question 18. Fill in the blanks

1. Tuberculosis is caused by a bacterium-called __________. The bacterium releases a toxin called _________.
2. Cholera is caused by the bacterium __________.
3. Typhoid is caused by a rod-shaped and motile bacterium called _________.

Answer. 1) Mycobacterium tuberculosis, tuberculin

2) Vibrio cholerae.

3) Salmonella typhi

Question 19. Spot the errors in the given statements and correct them.

1. Symptoms of pulmonary TB include swelling and tenderness of lymph glands, often in the leg which may discharge secretion through the skin.
2. The person suffering with Lymph T.B. has continuous fever, persistent cough and produces blood stained sputum.

Answer. Both are incorrect.

Question 20. Say True or False

1. Chloromycetin cure typhoid.
2. Diarrhoea is an abnormally frequent discharge of semisolid or fluid faeces.

Answer. 1) True 2) True

Question 21. Statement – I: The causative agents of diarrhoea are mainly bacteria such as Escherichia coli, Clostridium botulinum, Shigella dysentiriae, Campylobacter jejuri and Salmonella .
Statement – 2:Anthrax is an acute infectious disease caused by a rod-shaped non-motile bacterium called Bacillus anthracis.

1. Statement – 1 is true, Statement – 2 is false.
2. Statement – 1 is false, Statement – 2 is true.
3. Both statements are true.
4. Both statements are false.

Answer. Both statements are true.

Question 22. (1) Give two examples of viral diseases.

Answer. Common cold, Influenza , Dengue fever Poliomyelitis

(2) Give two examples of bacterial diseases.

Answer. Typhoid fever, Cholera, Tuberculosis Anthrax

(3) Give one examples of protozoan diseases.

Answer. Malaria, Kala-azar, Amoebic dysentry, Sleeping sickness

Question 23. (1) What is infective agent of peptic ulcers ?

Answer. Helicobacter pylori

(2) Who were awarded Nobel Prize for discovery of treatment for peptic ulcers ?

Answer. Marshall and Warren

Question 24. Name the disease in which

(a) Patient fears from water; (b) Yellowing of skin takes place.

Answer. Hydrophobia

Question 25. (1) Name one sexually transmitted viral disease.

Answer. AIDS

(2) What is full form of ORS ?

Answer. Oral Rehydration Solution

(3) Name the causal organism and vector of malaria respectively.

Answer. Plasmodium, Female Anopheles mosquito

Question 26. (1) Name the causal organism of (a) Tuberculosis; (b) Typhoid.

Answer. Mycobacterium tuberculosis, Salmonella typhi

(2) Name two diseases against which vaccines are available.

Answer. Diphtheria, Tetanus, Hepatatis

(3) Write full form of AIDS.

Answer. Acquired Immuno Deficiency Syndrome

Question 27. (1) Name two domestic animals which transmit rabies to human beings.

Answer. Dogs, rabbits or cats

(2) Name two modes of transmission of AIDS.

Answer. Unprotected sexual contact, Tranfusion of blood from infected person.

(3) Mention two preventive measures against rabies.

Answer. Cleaning the wound with carbolic soap, Any antiseptic medicine (e.g., Savalon, Dettol) should be applied to the wound

Question 28. (1) Name the toxin released by tuberculosis bacteria.

Answer. Ttuberculin

(2) Write down the modes of transmission of tuberculosis.

Answer. Conceptual

(3) Name the disease in which legs become paralysed.

Answer. Polio

Question 29. (1) When was the Pulse Polio Immunization Programme launched in India ?

Answer. December, 1995

(2) What is full form of BCG ?

Answer. Bacillus-Calmette-Guerin

(3) Name the causal organism of diarrhoea.

Answer. Escherichia coli, Clostridium botulinum

Question 30. (1) Name the disease the child will not suffer from if BCG vaccine is given.

Answer. Tuberculosis

(2) Name any three diseases of human beings caused by bacteria and three diseases caused by virus.

Answer. Common cold, Influenza ,Dengue fever are viral diseases.Cholera, Tuberculosis, Anthrax are bacterial diseases.

(3) How does dehydration set in during diarrhoea ?

Answer. Conceptual

Chapter 4 Why Do We Fall Ill Competitive Worksheet

Question 1. is an example of a bacterial disease that spreads through . The information in which alternative completes the given statement?

1. 1- Cholera 2- air
2. 1- Common cold 2- water
3. 1- Common cold 2- air
4. 1- Cholera 2- water

Answer. 4. 1- Cholera 2- water

Question 2. AIDS virus affects the body’s immune system. Which of the following acts does not lead to the transmission of AIDS?

1. Transfusion of blood from an infected person to a healthy person
2. Sexual act between an infected person and a healthy person
3. Breast feeding of baby by an infected mother
4. Handshake with an infected person

Answer. 4. Handshake with an infected person

Question 3. and are examples of diseases caused by protozoans. The information in which alternative completes the given statement?

1. 1- Dengue 2- influenza
2. 1- Influenza 2- Malaria
3. 1- Malaria 2- kala-azar
4. 1- Kala-azar 2- dengue

Answer. 3. 1- Malaria 2- kala-azar

Question 4. Viruses cause a number of diseases in humans. Which of the following diseases is caused by viruses?

1. Anthrax
2. Influenza
3. Cholera
4. Malaria

Answer. 2. Influenza

Question 5. Infectious diseases are diseases that spread through microbes, whereas non- infectious disease are diseases that are caused due to abnormalities in the internal structure of the body or its functioning. Which of the following diseases is non-infectious?

1. Cancer
2. Typhoid
3. Cholera
4. Malaria

Answer. 1. Cancer

Question 6. is a chronic disease as it affects the body for a duration of time. The information in which alternative completes the given statement?

1. 1- Tuberculosis 2- long
2. 1- Cough 2- short
3. 1- Tuberculosis 2- short
4. 1- Cough 2- long

Answer. 1. 1- Tuberculosis 2- long

Question 7. Tuberculosis is a disease, which affects the .The information in which alternative completes the given statement?

1. 1- acute 2- digestive system
2. 1- chronic 2- respiratory system
3. 1- chronic 2- digestive system
4. 1- acute 2- respiratory system

Answer. 2. 1- chronic 2- respiratory system

Question 8. Vaccines are small doses of a particular disease-causing microbe injected into the body of an individual. They act by fooling our immune system. Which of the following statements is incorrect regarding the given information?

1. Vaccines prevent the occurrence of the disease.
2. Vaccines induce memory for the particular infection.
3. Vaccines block the entry of disease-causing microbes.
4. Vaccines mimic the action of the disease-causing microbe.

Answer. 3. Vaccines block the entry of disease-causing microbes.

Question 9. Penicillin was the first antibiotic to be discovered. It is effective against most bacterial disease, but is ineffective against fungal diseases. Which of the following reasons correctly explains the given observation?

1. Fungal cells do not have a cell wall.
2. Bacteria are smaller in size when compared to fungi.
3. Fungal cells produce chemicals, which destroy penicillin.
4. Bacterial cells and fungi have dissimilar biochemical pathways.

Answer. 4. Bacterial cells and fungi have dissimilar biochemical pathways.

Question 10. Japanese Encephalitis is a vector-borne disease that transmits through the bite of mosquitoes. Which of the following organs is mainly affected by this disease?

1. Lungs
2. Liver
3. Brain
4. Stomach

Answer. 3. Brain

Question 11. Diseases can be transmitted from one person to another by many means. A particular disease is transmitted through direct contact, but cannot be transmitted by hugging or shaking hand. Which of the following diseases best suits the given mode of transmission?

1. Cholera
2. Syphilis
3. Kala-azar
4. Common cold

Answer. 2. Syphilis

Question 12. Helicobacter pylori is a . It causes peptic ulcers, which is a disease. The information in which alternative completes the given statement?

1. 1- bacteria 2- chronic
2. 1- protozoan 2- Acute
3. 1- bacteria 2- Acute
4. 1- protozoan 2- chronic

Answer. 1. 1- bacteria 2- chronic

Question 13. Which type of diseases can be prevented by controlling the breeding of mosquitoes?

1. Air-borne
2. Food-borne
3. Water-borne
4. Vector-borne

Answer. 4. Vector-borne

Question 14. Vaccines are available for which of the following diseases?

1. Polio
2. Malaria
3. Diabetes
4. Dengue

Answer. 1. Polio

Question 15. Antibiotic penicillin is ____1______ against common cold, which is caused by a ____2______. The information in which alternative completes the given statement?

1. 1- ineffective 2- protozoan
2. 1- ineffective 2- virus
3. 1- effective 2- protozoan
4. 1- effective 2- virus

Answer. 2. 1- ineffective 2- virus

Question 16. Supply of safe drinking water helps prevent ____1_____ diseases, while a clean environment helps prevent ____2_____ diseases. The information in which alternative completes the given statement?

1. 1- vector-borne 2- sexually transmitted
2. 1- sexually transmitted 2- air-borne
3. 1- air-borne 2- water-borne
4. 1- water-borne 2- vector-borne

Answer. 4. 1- water-borne 2- vector-borne

Question 17. Which of the following diseases cannot be prevented by vaccination?

1. Tetanus
2. Diphtheria
3. Common cold
4. Whooping cough

Answer. 3. Common cold

Question 18. Penicillin is an antibiotic that blocks the formation of ____1______. Hence, it is effective against ____2______. The information in which alternative completes the given statements?

1. 1- cell membrane 2- virus
2. 1- cell membrane 2- bacteria
3. 1- cell wall 2- virus
4. 1- cell wall 2- bacteria

Answer. 3. 1- cell wall 2- virus

Question 19. Malaria-causing microbes enter the body through mosquito bites. They first infect the _____1______ and then the _____2______. The information in which alternative completes the given statements?

1. 1- stomach 2- white blood cells
2. 1- stomach 2- red blood cells
3. 1- liver 2- white blood cells
4. 1- liver 2- red blood cells

Answer. 4. 1- liver 2- red blood cells

Question 20. Which of the following statements about sexually transmitted diseases is incorrect?

1. AIDS is a sexually transmitted disease
2. Syphilis is a sexually transmitted disease
3. Sexually transmitted diseases spread through handshakes
4. Sexually transmitted diseases spread through sexual contact

Answer. 4. Sexually transmitted diseases spread through sexual contact

Question 21. A water-borne disease such as _____1______ is more likely to spread in the ____2______ of safe supplies of drinking water. The information in which alternative completes the given statement?

1. 1- pneumonia 2- presence
2. 1- pneumonia 2- absence
3. 1- cholera 2- presence
4. 1- cholera 2- absence

Answer. 3. 1- cholera 2- presence

Question 22. Which of the following statements about air-borne diseases is correct?

1. Air-borne disease cannot spread through dust particles
2. Air-borne diseases spread easily in crowded areas
3. Pneumonia is not an air-borne disease
4. Typhoid is an air-borne disease

Answer. 2. Air-borne diseases spread easily in crowded areas

Question 23. Tuberculosis-causing bacteria enter the body through

1. nose
2. mouth
3. mosquito bite
4. sexual contact

Answer. 1. nose

Question 24. Diseases such as _____1______ and AIDS are _____2______ diseases. The information in which alternative completes the given statement?

1. 1- cholera 2- water-borne
2. 1- cholera 2- sexually transmitted
3. 1- syphilis 2- water-borne
4. 1- syphilis 2- sexually transmitted

Answer. 4. 1- syphilis 2- sexually transmitted

Question 25. Which of the following statements about water-borne diseases is incorrect?

1. Water-borne diseases spread through physical contact with the person infected by the disease
2. Water-borne diseases spread through the consumption of contaminated water
3. Typhoid is a water-borne disease
4. Cholera is a water-borne disease

Answer. 1. Water-borne diseases spread through physical contact with the person infected by the disease

Question 26. Which of the following statements is incorrect?

1. Air-borne diseases can spread through dust particles
2. Air-borne diseases spread easily in crowded areas
3. Pneumonia is an air-borne disease
4. Hepatitis A is an air-borne disease

Answer. 4. Hepatitis A is an air-borne disease