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.


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