Biology IX | Health and Diseases | Part 2

Health and Diseases | Part 2

Disease caused by bacteria

Tuberculosis (T.B.)

Tuberculosis (T.B.) was first discovered by Robert Koch in 1882. It is caused by a bacterium called Mycobacterium tuberculosis. The bacterium releases a toxin called tuberculin. T.B. can affect all parts of the body. In human beings, the infection spreads by inhaling infected droplets released through coughing, sneezing, talking and spitting by the patient.


The patient feels sick and weak. There is a loss of appetite and weight. Fever rises on the afternoon and falls by morning. Two specific sites of infection are :

(i) Lung (Pulmonary) T.B. :

In any tuberculosis the person has persistent cough and produces blood stained sputum. There is loss of weight, and weakness, Chest pain and breathlessness are common features.

(ii) Lymph Gland T.B. :

Swelling and tenderness of lymph glands, often in the leg, which may discharge secretions through the skin.

Prevention :

Immunization with BCG or Bacillus-Calmete-Guerin vaccination in which weakened Tuberculosis bacillus is injected which prevents tuberculosis

Control :

By the use of Anti-tubercular therapy (ATT).

Cholera :

It is more common during fairs and after floods. Sometimes it occurs in epidemic form spread over large population. Cholera is caused by the bacterium Vibrio cholerae. It is transmitted by flies, contaminated water and food.


(i) Effortless vomiting without nausea

(ii) Loss of several litres of fluid within hours, which causes dehydration, muscle cramps and weight loss.

(iii) Eyes become shunken


(i) Immunization by standard cholera vaccine.

(ii) Boiled water and cooked food should be taken

(iii) Careful, personal hygiene and good sanitation

(iv) Oral rehydration therapy (Sodium chloride 3.5 g, Sodium bicarbonate – 2.5 g, potassium chloride – 1.5 g, Glucose 20.0g, Surcrose – 40g in one litre water) should be used immediately. Taking small sips of this solution at intervals prevents dehydration.

Control :

Immediate medical advice should be taken.


Typhoid is common in the age group of 1 – 15 years. Every year 2.5 million persons suffer from typhoid. Typhoid is caused by the bacteria Salmonella typhi commonly found in intestine of man.


(i) Headache and typhoid fever which rise to the maximum in the afternoon. Also the temperature increases each day in the first weak.

(ii) High fever in the second week and then gradually declines during third and fourth week.


(i) TAB-vaccination provides immunity for 3 years.

(ii) Typhoral oral vaccine also prevents typhoid

Control :

There are standard drugs against typhoid which cure the disease.


Diarrhoea is frequent loose motions. Causal organism of diarrhoea are certain types of bacteria (E.coli, Shigella spp.) protozoa and viruses.


(i) Frequent loose motion and vomiting leading to dehydration.

(ii) 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.


(i) Stale food should not be consumed

(ii) Personal and community hygiene is important

Control :

Complete bed rest.


(i) Headache and typhoid fever which rise to the maximum in the afternoon. Also the temperature increases each day in the fist week.

(ii) ‘Rehydration fluid’ which can be easily made by adding one teaspoon of sugar and a pinch of salt to 200 mL of water. It is called oral rehydration solution (ORS).

(iii) Use antimicrobial drugs and anti-diarhoeal agents to treat diarrhea.

(iv) Pulp of boiled unripe banana along with required amount of salt, turmeric powder and lime is helpful in controlling diarrhea.

(v) Husk of isabgol seed (Plantago ovata) with water or curd provides relief.


Anthrax is an acute infectious disease caused by bacterium – Bacillus anthracis. This disease commonly orrurs in wild and domestic animals such as cattle, sheep, goat, but it can also infect humans when they are exposed to infected animals.

Symptoms :

Anthrax infection can occur in three forms : Coetaneous (skin), inhalation and gastroinstestinal.

Coetaneous :

About 20% of untreated cases of coetaneous anthrax will result in death. Coetaneous cases are rare.

Inhalation :

It resemble to a common cold leading to severe breathing problems.

Intestinal anthrax :

The symptoms are nausea, loss of appetite, vomiting, pain, and vomiting blood. Results in death in 25% to 60% cases.

Prevention :

Vaccine is reported to be 93% effective in protecting against anthrax.

Control :

Doctor can prescribe effective antibiotic.

Means of Spread of Infectious diseases

1. Air-borne disease.

Those diseases causing microbes spread through air known as air-borne diseases e.g. common cold, pneumonia and tuberculosis

2. Water borne disease.

Those diseases causing microbes spread through water known as air-borne diseases e.g. cholera, diarrhea

3. Sexually-transmitted disease.,

e.g., Syphilis and AIDS. Both of these pathogens are transmitted bisexual contact from one partner to the other. However, such sexually, such 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.

4. Spread of disease through vectors.

Many animals which live with us may carry diseases. These animals carry the infecting agents from a sick person to another potential host. Thus, these animals act as intermediaries or vectors. Vectors are carrier of a diseases or infection. 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. Hence, they feed on many warm-blooded animals including us.

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 requirement, we can provide treatment that will reduce the symptoms. The symptoms are usually because of inflammation. For example, we can take medicines that bring down fever, reduce pain or loose motions. We can take bed rest so that we can conserve our energy. This exercise will enable us to focus on the healing.

Principles of Prevention of Disease

Following three limitations 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. This means that if someone suffering from a disease, he is like to bedridden for sometime, even if we given him proper treatment.

3. The person suffering from an infectious disease can serve as the source from where the infection may spread to other people.


Biology IX | Health and Diseases | Part 1

Health and Diseases | Part 1

Human Diseases

Definition :

Disease may be defined as a disorder in the physical, physiological, psychological or social state of a person caused either due to nutritional deficiency, hormonal disorder, genetic disorder, pathogen or any other reason.

Types of Diseases

Diseases are broadly grouped into two categories :

a. Congenital diseases

b. Acquired diseases

Congenital Diseases :

These diseases are those which are present since birth. They are caused due to a genetic abnormality or due to metabolic disorders or malfunctioning of any organ or organ system. These disease may be inherited.

Acquired Diseases :

These diseases are those which develop after birth. These can be broadly classified into two types :

(a) Communicable (Infectious) Diseases

These are caused by the attack of microorganism (Pathogens) such as bacteria, viruses, fungi or protozoans. The causal organism of the disease can be transmitted from one person to another by means of air, water, food, physical contact and insects (vectors). Hence, these are called communicable diseases that are communicated from diseases person to healthy person.

(b) Non-Communicable (Non-Infectious) Diseases

The diseases which do not spread from infected person to healthy person are known as non-communicable or non-infectious diseases, such as diabetes, arthritis, heart diseases, cancer, etc. Many non-communicable diseases are due to nutritional deficiency.

Disease caused by Protozoa

Malaria :

Health experts estimate that bout 300 million people are infected with malaria every year and more than 2 million die annually due to malaria. Malaria is caused by a protozoan parasite Plasmodium. This spreads through the bite of an insect vector-female anopheles mosquito which feeds on human blood (male anopheles mosquito feed upon plant juices).

Symptoms :

Headache, nausea, muscular pains and high fever are the main symptoms of malaria. Each malarial attack is of 6 – 10 hours and consists of three states : cold stage feeling very cold and shivering), hot stage (high fever, faster respiration and heart beat) and sweating stage (in which temperature goes down to normal). Malaria may also secondarily cause enlargement of spleen and liver.

Macculoch (1827) proposed the name malaria. Laveran (1880) discovered the malarial parasite Plasmodium in the blood of malarial patient.


1. Use wire-guaze on doors and windows to prevent entry of mosquitoes.

2. Use insect-repellents to prevent mosquito-bite.

3. Sleep under mosquito net.

4. Mosquito larvae should be killed by sprinkling kerosene oil, Cambusia, minnows, trouts and birds (ducks) etc.

5. Kill adult mosquitoes by spraying insecticides

6. Destroy mosquito-breeding places

Control :

A drug named quinine (extracted from the bark of Cinchona tree) is used to treat a person suffering from malaria.

Disease caused by Viruses

Influenza (Flu) :

Symptoms of influenza (Flue) are common cold, cough and fever. It is an air borne disease. The cause disease is a virus called Myxovirus influenzae.

Symptoms :

Sneezing, coughing, fever, etc. are the main symptoms of this disease.

Prevention :

Try to keep away from flue patients.

Control :

There is no effective control for influenza.

Jaundice / Hepatitis :

Jaundice or hepatitis is the disease of liver. Jaundice is caused by viral infection. The types of hepatitis are : Hepatitis – A, B, C, D, E or G Disease is spread mostly by food and water contaminated with hepatitis.


(i) High temperature, headache and joint pains.

(ii) Loss of appetite with a feeling of nausea and vomiting.

(iii) Dark yellow urine and light-coloured stool after 3 to 10 days.


(i) Use chlorinated, boiled and ozonised water.

(ii) Hepatitis – B vaccine should be taken to prevent the disease.


(i) Interferon injection administered on the advice of the doctor will control the disease.

(ii) Adequate rest is essential for an early cure.


Acquired Immuno Deficiency Syndrome (AIDS) is a fatal disease in which immune system of the body is seriously affected. It was first detected in June 1981 in USA. The cause of the disease is a retrovirus-HIV (human immuno deficiency virus). The disease is transmitted from an infected person to healthy person through sexual contact, blood transfusion, use of contaminated needles or blade, or razors and other equipment of barbers and also from infected mother to the foetus.


(i) Decreased count of blood platelets causing haemorrhage and fever.

(ii) Sweating at night and weight loss

(iii) Severe damage to brain which may lead to loss of memory, ability to speak and even think

(iv) Patient becomes susceptible to other infections due to breakdown of immune system


Educating the people for the following :

(i) No common razor should be used.

(ii) A blood donor should be first tested HIV negative.

(iii) Disposable needles and syringes should be used

(iv) Sexual contact with unknown people should be avoided.

Control :

Till date there is no effective treatment for AIDS.