CG Board Class 8 Science Chapter 16 Solutions: Some Common Diseases (कुछ सामान्य रोग) – 2026-27

Diseases caused by protozoan parasites mentioned in the textbook are Malaria (caused by Plasmodium) and Amoebiosis / Amoebic Dysentery (caused by Entamoeba histolytica).

The main cause for the spread of malaria is the bite of an infected female Anopheles mosquito, which transmits the malarial parasite Plasmodium from an infected person to a healthy person.

The first aid provided to a person having frequent bowels and diarrhoea is administering Oral Rehydration Solution (ORS) or home-made rehydration fluids like coconut water, salty buttermilk, lemon juice, rice starch water (maand), light tea, or boiled pulse water (dal water) frequently to prevent dehydration (loss of water and essential salts from the body).

Name of Malarial Parasite:* Plasmodium* (a protozoan parasite).

• Name of Carrier / Vector: Female Anopheles mosquito.

The symptoms of chicken pox are

1. Mild to moderate fever in the patient.
2. Uneasiness, body pain, backache, and pain in joints.
3. Appearance of red rashes/spots on the body. Rashes start from the neck, face, and spread to lower parts and legs, which form scales (crusts) after 4 to 7 days.

The polio virus enters through the digestive tract, multiplies in the intestine walls, enters the blood vessels, and then attacks the central nervous system (nerves controlling leg muscles), causing paralysis of muscle movement.

OPV stands for Oral Pulse Vaccine (or Oral Polio Vaccine), which is administered orally in drop form to children from birth up to 5 years of age to develop immunity against the polio virus.

Polio is spread primarily through infected food, water, and direct contact with the excreta (stools) or throat discharges of an infected person, carried by houseflies and unhygienic conditions.

The main symptoms of rabies (hydrophobia) are

1. Hydrophobia (extreme fear of water).
2. High fever, severe headache, and high restlessness/nervousness.
3. Blockage and spasms in the throat muscles, suppressing the voice.
4. Paralysis due to damage/bursting of nerve cells in the central nervous system.

The full form of the AIDS virus is Human Immunodeficiency Virus (HIV). (The full form of AIDS itself is Acquired Immune Deficiency Syndrome).

Symptoms of sickle cell anaemia are

1. Pale or white appearance of the body due to lack of blood (anaemia).
2. Extreme fatigue and heavy/shortness of breathing.
3. Irritability and loss of appetite.
4. Swelling and pain in fingers, toes, and joints.
5. Frequent cold and fever, enlarged spleen, and stunted/hindered growth in children.

(1) T.A.B vaccine is against typhoid.**

Correct Statement. T.A.B. vaccine provides protection against typhoid fever.

(2) Tuberculosis is caused by Vibrio cholerae.

Incorrect Statement.

• Corrected Statement: Tuberculosis is caused by Mycobacterium tuberculosis bacteria, whereas Vibrio cholerae causes cholera.

(3) To prevent mosquito bite, mosquito nets must be used.

Correct Statement. Mosquito nets protect against mosquito bites and prevent vector-borne diseases like malaria and filaria.

(4) Excreta of the persons from dysentry and diarrhoea must not be left open, but be covered by sand or ash.

Correct Statement. Covering excreta prevents houseflies from carrying disease pathogens to food and water.

(5) Using the handkerchiefs and towels used by a person suffering from cold and flu, does not affect a healthy person.

Incorrect Statement.

• Corrected Statement: Using handkerchiefs and towels used by a person suffering from cold and flu can easily transmit the virus to a healthy person.

(6) To prevent filarial mosquitoes must be destroyed.

Correct Statement. Filaria is transmitted by Culex mosquitoes, so destroying mosquitoes prevents filaria.

(7) Rabies is caused by the bite of any dog or cat.

Incorrect Statement.

• Corrected Statement: Rabies is caused by the bite of a rabies-infected animal (dog, cat, monkey, etc.) carrying the rabies virus in its saliva, not by any uninfected healthy animal.

(1) Disease caused by bacteria and virus is:**

(a) hereditary disease

(b) contagious / communicable disease

(c) scurvy

(d) non contagious disease

(b) contagious / communicable disease

(2) BCG is used against:

(b) tuberculosis

(3) Which is a bacteria borne disease?

(b) typhoid (caused by Salmonella typhi)

(4) Malaria is spread by:

(c) female anopheles mosquito

(5) Chill and shivering is a symptom of which disease:

(c) malaria

(6) The disease caused by a protozoa is:

(a) dysentry

(7) Dysentry is caused due to:

(a) drinking contaminated water

Preventive measures against tuberculosis (T.B.) are

1. Administering BCG (Bacillus Calmette Guerin) vaccine to infants.
2. Isolating the T.B. patient in a clean, ventilated room away from other family members.
3. Asking the patient to cover their mouth with a cloth while coughing or sneezing.
4. Proper disposal of the patient’s spit/phlegm by covering it with ash or soil and burying it in a hole.
5. Avoiding overcrowding, dark, and dust-polluted environments, and maintaining proper nutrition.
6. Completing a full course of anti-tuberculosis medical treatment under doctor’s guidance.

Definition:** Dehydration is the excessive loss of water and essential mineral salts from the body caused by frequent vomiting and watery stools.

• Treatment / Management:

1. Give Oral Rehydration Solution (ORS) frequently. ORS can be prepared at home by boiling 1 cup (200 ml) of clean water, letting it cool, and adding a pinch of salt, one teaspoon of sugar, and half a lemon juice.
2. Provide home-available fluids such as coconut water, salty buttermilk, rice starch water (maand), light tea, or dal water.
3. Keep the patient hydrated and consult a doctor immediately if severe.

Stagnant water pits near the house serve as breeding grounds for mosquitoes. If mosquitoes breed there, you may get infected with mosquito-borne communicable diseases such as

1. Malaria: Caused by Plasmodium parasite transmitted by female Anopheles mosquitoes.
2. Filaria (Elephantiasis): Caused by Wuchereria bancrofti worm transmitted by Culex mosquitoes.

Disease: The friend is most likely suffering from Amoebiosis (Amoebic Dysentery) or Diarrhoea**.

• Reason: Abdominal cramps, muscle spasms in the stomach, and frequent bowel discharge containing mucus/blood are primary characteristic symptoms of Amoebiosis (caused by Entamoeba histolytica protozoa). If the stools are continuous and watery, it indicates Diarrhoea.

1. Common Cold (Rhinovirus):

• Symptoms: Frequent sneezing, profuse watery nasal discharge, red and swollen nose, blocked nose, mild fever, and sore throat.

1. Polio (Poliovirus):

• Symptoms: Fever, cold and cough, neck muscle cramps, shrinking of leg muscle fibers, and paralysis of leg movement leading to lameness.

Filaria (Filariasis or Elephantiasis)* is a disease caused by a thread-like worm called Wuchereria bancrofti, transmitted through Culex* mosquito bites.

Houseflies act as mechanical carriers that transmit pathogens from excreta/garbage to food and water. Diseases spread by flies include

1. Cholera (caused by Vibrio cholerae)
2. Typhoid (caused by Salmonella typhi)
3. Amoebiosis / Dysentery (caused by Entamoeba histolytica)
4. Diarrhoea

It is necessary for prospective brides and grooms to undergo blood tests before marriage to check for genetic disorders, specifically Sickle Cell Anaemia.

• Reason: Sickle cell anaemia is an inherited genetic disorder. If two sickle cell carriers (or a carrier and a sufferer) marry, there is a high probability that their children will be born suffering from severe sickle cell anaemia. Blood matching ensures that carriers do not unknowingly marry another carrier, thereby preventing the transmission of this genetic disorder to the next generation.