Human Diseases — Set 1

Correct Answer: C. Malaria

• **Malaria** = caused by the protozoan parasite *Plasmodium* (P. falciparum, P. vivax, etc.), injected into the bloodstream when a female Anopheles mosquito bites a human host. • **Plasmodium life cycle** — the parasite multiplies inside red blood cells, rupturing them periodically and causing the classic cycle of fever, chills, and sweating every 48–72 hours. • Malaria kills over 600,000 people annually, mostly in sub-Saharan Africa and South Asia, making it one of the deadliest vector-borne diseases on Earth. • 💡 Option A (Filaria) is wrong because it is caused by a nematode worm (*Wuchereria bancrofti*) spread by *Culex* mosquitoes; Option B (Dengue) is wrong because it is a viral disease spread by *Aedes aegypti*; Option D (Chikungunya) is wrong because it is also a viral disease spread by *Aedes* mosquitoes, not Anopheles.

Correct Answer: D. Vitamin D

• **Vitamin D** = its deficiency causes Rickets in children — a condition where bones become soft, weak, and deformed (bowed legs, enlarged skull) because calcium and phosphorus cannot be properly absorbed and deposited in bone tissue. • **Vitamin D sources** — synthesised in the skin on exposure to sunlight (UV-B); also obtained from fatty fish, egg yolk, and fortified milk; adults with the same deficiency develop Osteomalacia. • Rickets was historically called the "English disease" because industrial smog in 19th-century Britain blocked sunlight for large urban populations. • 💡 Option A (Vitamin K) is wrong because its deficiency causes poor blood clotting, not bone deformity; Option B (Vitamin A) is wrong because its deficiency causes Night Blindness and Xerophthalmia; Option C (Vitamin C) is wrong because its deficiency causes Scurvy.

Correct Answer: B. Lungs

• **Lungs** = Tuberculosis (TB) is caused by the bacterium *Mycobacterium tuberculosis*, which primarily attacks lung tissue, forming granulomas called tubercles — giving the disease its name. • **TB transmission** — spreads through airborne droplet nuclei when an infected person coughs, sneezes, or speaks; untreated pulmonary TB has a fatality rate of ~50%, but the BCG vaccine and antibiotics have dramatically reduced deaths. • TB can also affect other organs (bone, kidney, brain — called extra-pulmonary TB), but the lungs are the primary and most common site. • 💡 Option A (Kidneys) is wrong because kidney disease is not the hallmark of TB, though renal TB can occur secondarily; Option C (Liver) is wrong because the liver is primarily affected by Hepatitis, not TB; Option D (Heart) is wrong because cardiac diseases are caused by entirely different pathogens or lifestyle factors.

Correct Answer: C. Mercury

• **Mercury** = Minamata disease is caused by methylmercury poisoning, which bioaccumulates in seafood; residents of Minamata Bay, Japan, ate fish contaminated by industrial wastewater from the Chisso Corporation's chemical plant throughout the 1950s. • **Neurological effects** — methylmercury crosses the blood-brain barrier, causing brain damage, sensory loss, loss of coordination (ataxia), tunnel vision, and in severe cases, paralysis and death; it is especially devastating to unborn children. • The Minamata Convention on Mercury (2013) is an international treaty named after this disaster, aiming to protect human health from anthropogenic mercury emissions. • 💡 Option A (Cadmium) is wrong because cadmium poisoning causes Itai-Itai disease (bone and kidney damage), not Minamata; Option B (Arsenic) is wrong because arsenic causes skin lesions, cancer, and arsenicosis; Option D (Lead) is wrong because lead poisoning causes neurological damage in children but is called plumbism, not Minamata disease.

Correct Answer: A. Hepatitis

• **Hepatitis** = a viral infection of the liver causing inflammation; the damaged liver cannot process bilirubin normally, leading to its buildup in blood and tissues — producing the characteristic yellow discolouration of skin and eyes called jaundice. • **Types of Hepatitis** — Hepatitis A and E spread via contaminated food/water (faecal-oral route); Hepatitis B, C, and D spread via blood, sexual contact, or mother to child; Hepatitis B and C can progress to chronic liver disease, cirrhosis, and liver cancer. • Hepatitis B is the world's most common serious liver infection, with over 296 million people chronically infected globally. • 💡 Option B (Typhoid) is wrong because it is a bacterial disease caused by *Salmonella typhi*, primarily affecting the intestines, not the liver with jaundice; Option C (Cholera) is wrong because it causes severe watery diarrhoea, not liver inflammation or jaundice; Option D (Amoebiasis) is wrong because it is a parasitic infection of the large intestine.

Correct Answer: C. Typhoid

• **Typhoid** = the Widal Test is a serological agglutination test that detects antibodies (agglutinins) produced against the O and H antigens of *Salmonella typhi* in the patient's blood serum, confirming typhoid fever infection. • **Typhoid transmission** — *Salmonella typhi* spreads via contaminated food and water (faecal-oral route); symptoms include sustained high fever, headache, rose spots on the abdomen, and relative bradycardia; treated with ciprofloxacin or azithromycin. • The Widal test was developed in 1896 by French physician Georges-Fernand Widal and remains one of the most widely used typhoid diagnostic tools in developing countries. • 💡 Option A (Malaria) is wrong because malaria is diagnosed by blood smear microscopy or the RDT (Rapid Diagnostic Test), not Widal; Option B (Pneumonia) is wrong because pneumonia is diagnosed by chest X-ray and sputum culture; Option D (Yellow Fever) is wrong because it is diagnosed by PCR or IgM antibody ELISA, not the Widal test.

Correct Answer: B. Vitamin C

• **Vitamin C (Ascorbic acid)** = its deficiency causes Scurvy because Vitamin C is essential for collagen synthesis; without adequate collagen, blood vessel walls weaken, causing bleeding gums, skin haemorrhages, poor wound healing, and loose teeth. • **Historical significance** — Scurvy devastated sailors on long voyages before the 18th century; the British Navy's discovery that citrus fruits (limes, lemons) cured scurvy led to the nickname "Limeys" for British sailors; Vitamin C cannot be synthesised by the human body and must be obtained from diet. • Amla (Indian gooseberry) contains the highest Vitamin C content among commonly available foods — approximately 600 mg per 100g. • 💡 Option A (Iron) is wrong because iron deficiency causes Anaemia, not Scurvy; Option C (Protein) is wrong because protein deficiency causes Kwashiorkor or Marasmus; Option D (Vitamin B1) is wrong because Thiamine deficiency causes Beri-beri, not Scurvy.

Correct Answer: D. Diabetes Mellitus

• **Diabetes Mellitus** = characterised by chronically elevated blood glucose (hyperglycaemia) due to either insufficient insulin production by pancreatic beta cells (Type 1) or insulin resistance in body cells (Type 2); the classic symptoms are polyuria, polydipsia, and polyphagia. • **Insulin role** — insulin is a hormone secreted by the islets of Langerhans in the pancreas; it enables cells to absorb glucose from the bloodstream; without it, glucose accumulates in blood, spills into urine (glycosuria), and cells are starved of energy. • India is known as the "Diabetes Capital of the World" with over 100 million diabetics, the highest count globally. • 💡 Option A (Anaemia) is wrong because it involves reduced haemoglobin/RBC count, not blood sugar; Option B (Goitre) is wrong because it results from iodine deficiency causing thyroid gland swelling; Option C (Diabetes Insipidus) is wrong because it is a completely different disorder caused by ADH deficiency, resulting in excessive urination without elevated blood sugar.

Correct Answer: D. Entamoeba histolytica

• **Entamoeba histolytica** = a protozoan parasite that invades the mucosa of the large intestine, causing inflammation, ulceration, and bloody diarrhoea (dysentery); it spreads via contaminated food and water through the faecal-oral route. • **Cyst stage** — the parasite survives outside the body as cysts in contaminated water; once ingested, cysts transform into active trophozoites in the intestine; in severe cases, the parasite can migrate to the liver, causing amoebic liver abscess. • Amoebic dysentery must be distinguished from bacillary dysentery (caused by *Shigella* bacteria) — amoebic dysentery is treated with metronidazole. • 💡 Option A (Plasmodium vivax) is wrong because it causes malaria, not dysentery; Option B (Vibrio cholerae) is wrong because it causes Cholera — profuse watery diarrhoea without blood; Option C (Escherichia coli) is wrong because though some strains can cause diarrhoea, classic amoebic dysentery is specifically caused by *E. histolytica*.

Correct Answer: D. Iodine

• **Iodine** = the thyroid gland requires iodine to synthesise the hormones thyroxine (T4) and triiodothyronine (T3); when iodine is deficient, the pituitary gland releases excess TSH to stimulate the thyroid, causing it to enlarge abnormally — the visible neck swelling called Goitre. • **Simple vs toxic goitre** — simple (endemic) goitre is caused by iodine deficiency and is common in mountainous inland regions far from the sea; iodised salt is the primary public health intervention to prevent it; severe iodine deficiency during pregnancy causes cretinism in the newborn. • India's salt iodisation programme began in the 1950s, dramatically reducing endemic goitre in high-risk Himalayan and hilly regions. • 💡 Option A (Magnesium) is wrong because magnesium deficiency causes muscle cramps and cardiac arrhythmias, not thyroid swelling; Option B (Calcium) is wrong because calcium deficiency causes rickets and osteoporosis; Option C (Iron) is wrong because iron deficiency causes Anaemia.