Chapter 7: Human Health and Disease Case Study Questions | biology Class 12 CBSE

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Chapter 7: Human Health and Disease Case Study Questions | biology Class 12 CBSE | ByteNotes.in

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Case Set 1

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Ramesh, a 10-year-old boy living in a rural area, started experiencing sustained high fever ranging between 39°C to 40°C, severe headache, weakness, stomach pain and loss of appetite for the past two weeks. His parents initially dismissed it as a seasonal flu. However, when his condition deteriorated and he complained of intense abdominal pain, they rushed him to a doctor. The doctor suspected a bacterial infection of the gastrointestinal tract and ordered specific diagnostic tests. The blood test confirmed the diagnosis. The doctor found out that the family had been consuming water from an unprotected well that was contaminated. The boy was admitted and given appropriate antibiotic treatment. The doctor also advised the family on safe drinking water practices.

Question 1: Name the disease Ramesh is most likely suffering from and identify its causative organism.

The disease is typhoid fever.
It is caused by the bacterium Salmonella typhi.

Question 2: Which diagnostic test would confirm this disease? How does the pathogen enter the human body?

Widal test is used to confirm typhoid fever.
The pathogen enters the human body through food and water contaminated with Salmonella typhi and then migrates to other organs through blood.

Question 3: What preventive measures should the family adopt to avoid such waterborne diseases in the future? Explain the role of personal and public hygiene.

Consume only clean and boiled or purified drinking water.
Proper disposal of waste and excreta to prevent contamination of water sources.
Periodic cleaning and disinfection of water reservoirs, pools and tanks.
Maintenance of standard hygiene practices in food preparation and handling.
Awareness about diseases spread through food and water is essential for prevention.

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Case Set 2

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During a biology practical, students were shown a slide of RBCs from a malaria patient. Their teacher explained that the patient, a 25-year-old man returning from a trip to a forested area in Assam, presented with recurring high fever and chills every 3-4 days, along with headache and muscle pain. Blood smear examination revealed the presence of a protozoan parasite inside the RBCs. The teacher pointed out that the rupture of infected RBCs released a toxic substance responsible for the fever. The patient had not taken prophylactic medication before his trip. The condition was identified as the most dangerous form of malaria, requiring urgent hospitalisation.

Question 1: Identify the species of Plasmodium responsible for this most dangerous form of malaria. What is the toxic substance released during RBC rupture?

Plasmodium falciparum is responsible for malignant (most dangerous) malaria.
The toxic substance released during RBC rupture is haemozoin, which causes chills and high fever.

Question 2: Describe the role of the female Anopheles mosquito in the life cycle of Plasmodium.

The female Anopheles mosquito acts as a vector (transmitting agent) for malaria.
When it bites an infected person, Plasmodium parasites enter the mosquito body, multiply and form sporozoites stored in its salivary glands.
When this mosquito bites a healthy person, sporozoites are introduced into the human body, initiating infection.

Question 3: What preventive and control measures should be adopted to reduce malaria transmission in the affected region? Discuss at least four measures.

Avoid stagnation of water in and around residential areas to eliminate mosquito breeding sites.
Regular cleaning of household coolers where mosquitoes breed.
Use of mosquito nets to prevent mosquito bites during sleep.
Introduce larvivorous fishes like Gambusia in ponds to feed on mosquito larvae.
Spray insecticides in ditches, drainage areas and swamps.
Provide wire mesh on doors and windows to prevent entry of mosquitoes.

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Case Set 3

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A 5-year-old girl was brought to a paediatrician with complaints of mild fever, abdominal cramps, and stools containing mucus and blood. The parents mentioned they had recently moved to a new city and noticed that the child's symptoms started after consuming street food and water of uncertain quality. The doctor suspected intestinal parasitosis. Microscopic examination of the stool sample revealed cysts of a protozoan parasite. The doctor also noted that houseflies are important carriers of this parasite. The child was prescribed appropriate medication. The doctor also counselled the parents on food and water hygiene.

Question 1: Name the disease and the causative organism. Where does this parasite reside in the human body?

The disease is amoebiasis (amoebic dysentery).
It is caused by Entamoeba histolytica, a protozoan parasite that resides in the large intestine of humans.

Question 2: How do houseflies contribute to the transmission of amoebiasis?

Houseflies act as mechanical carriers of Entamoeba histolytica.
They transmit the parasite by carrying it from the faeces of infected persons to food and food products, thereby contaminating them and spreading infection to healthy individuals.

Question 3: Explain the symptoms of amoebiasis and describe the preventive measures that should be adopted to control such diseases spread through food and water.

Symptoms include constipation, abdominal pain and cramps, and stools with excess mucous and blood clots.
Preventive measures: consume only clean, purified drinking water and properly washed food items.
Proper disposal of waste and excreta to prevent contamination of water and food.
Maintaining personal hygiene such as washing hands before eating and after using the toilet.
Avoiding consumption of street food from unhygienic sources.
Periodic disinfection of water reservoirs and public food-serving areas.

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Case Set 4

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During a health camp in a coastal village, doctors noticed several patients with grossly swollen limbs, particularly the legs. One patient, a 40-year-old fisherman, had been suffering from this condition for years. Upon examination, doctors found chronic inflammation of the lymphatic vessels. Blood smear examination at night revealed the presence of microfilariae. Doctors explained to the villagers that the condition was caused by parasitic worms transmitted through mosquito bites. The villagers were advised on mosquito control measures and given appropriate medication. The chronic and disfiguring nature of the disease had already significantly impaired the affected individuals' quality of life.

Question 1: Name the disease and the causative organisms responsible for it.

The disease is elephantiasis (filariasis).
It is caused by filarial worms Wuchereria bancrofti and Wuchereria malayi.

Question 2: What organs are commonly affected in elephantiasis and how is the disease transmitted?

The filarial worms commonly affect the lymphatic vessels of the lower limbs, causing chronic inflammation; the genital organs are also often affected.
The disease is transmitted through the bite of infected female mosquito vectors.

Question 3: Distinguish between ascariasis and filariasis with respect to causative organisms, mode of transmission and symptoms.

Ascariasis is caused by Ascaris (roundworm); filariasis is caused by Wuchereria bancrofti and W. malayi (filarial worms).
Ascariasis is transmitted through contaminated water, vegetables and fruits containing parasite eggs; filariasis is transmitted through the bite of infected female mosquitoes.
Ascariasis symptoms: internal bleeding, muscular pain, fever, anemia, blockage of intestinal passage.
Filariasis symptoms: chronic inflammation of lymphatic vessels of lower limbs, swelling (elephantiasis), and deformity of genital organs.

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Case Set 5

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Priya, a medical student, was studying a case of a patient who had recently received a kidney transplant. Despite matching blood groups and tissue types with the donor, the patient was experiencing graft rejection symptoms. The doctor explained that even after successful tissue matching, the body's immune mechanism recognised the transplanted organ as 'non-self' and initiated an immune response against it. The patient was put on immunosuppressant drugs for the rest of his life. Meanwhile, Priya was also reading about how the immune system sometimes mistakenly attacks the body's own tissues, leading to certain chronic diseases.

Question 1: Which type of immune response is responsible for graft rejection? Name the cells involved.

Cell-mediated immune response (CMI) is responsible for graft rejection.
T-lymphocytes (T-cells) mediate this response and are responsible for recognising and attacking the transplanted tissue.

Question 2: What is auto-immune disease? Give one example.

Auto-immune disease occurs when the immune system mistakenly attacks the body's own cells due to genetic or other unknown reasons, resulting in damage to the body's own tissues.
Example: Rheumatoid arthritis is an auto-immune disease that affects joints in many people.

Question 3: Explain the difference between humoral and cell-mediated immunity. What is the role of B-lymphocytes and T-lymphocytes in acquired immunity?

Humoral immunity involves B-lymphocytes producing antibodies (proteins) that circulate in the blood to fight pathogens; it is also called antibody-mediated immune response.
Cell-mediated immunity (CMI) is carried out by T-lymphocytes; these cells do not secrete antibodies but help B-cells to produce them and are responsible for graft rejection.
B-lymphocytes: produce antibodies (IgA, IgM, IgE, IgG) with H2L2 structure (two heavy and two light chains) in response to pathogens.
T-lymphocytes: mediate CMI, help B-cells produce antibodies, and are responsible for recognising and destroying foreign/non-self cells.
Both B and T lymphocytes carry immunological memory, enabling stronger secondary immune response.

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Chapter 7: Human Health and Disease | Case Study Questions

Passage

Question 1: Name the disease Ramesh is most likely suffering from and identify its causative organism.

Question 2: Which diagnostic test would confirm this disease? How does the pathogen enter the human body?

Question 3: What preventive measures should the family adopt to avoid such waterborne diseases in the future? Explain the role of personal and public hygiene.

Passage

Question 1: Identify the species of Plasmodium responsible for this most dangerous form of malaria. What is the toxic substance released during RBC rupture?

Question 2: Describe the role of the female Anopheles mosquito in the life cycle of Plasmodium.

Question 3: What preventive and control measures should be adopted to reduce malaria transmission in the affected region? Discuss at least four measures.

Passage

Question 1: Name the disease and the causative organism. Where does this parasite reside in the human body?

Question 2: How do houseflies contribute to the transmission of amoebiasis?

Question 3: Explain the symptoms of amoebiasis and describe the preventive measures that should be adopted to control such diseases spread through food and water.

Passage

Question 1: Name the disease and the causative organisms responsible for it.

Question 2: What organs are commonly affected in elephantiasis and how is the disease transmitted?

Question 3: Distinguish between ascariasis and filariasis with respect to causative organisms, mode of transmission and symptoms.

Passage

Question 1: Which type of immune response is responsible for graft rejection? Name the cells involved.

Question 2: What is auto-immune disease? Give one example.

Question 3: Explain the difference between humoral and cell-mediated immunity. What is the role of B-lymphocytes and T-lymphocytes in acquired immunity?

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