Human Health and Diseases MCQs for NEET — Zoology Questions with Answers

People get malaria by being bitten by an infective female Anopheles mosquito. Only Anopheles mosquitoes can transmit malaria and they must have been infected through a previous blood meal taken from an infected person.

Because the malaria parasite is found in red blood cells of an infected person, malaria can also be transmitted through blood transfusion, organ transplant, or the shared use of needles or syringes contaminated with blood. Malaria may also be transmitted from a mother to her unborn infant before or during delivery(vertical transmission through placental defect).

(c): Memory cells refer to memory B cells. It is a B cell sub-type that are formed following primary infection. When a B cell is activated, by recognising a specific antigen, it proliferates to form antibody producing plasma cells and long-lived memory cells. The memory B cells are specisics or the antigen that first stimulated their production. If this antigen is encountered again, memory B cells can recognise it and quickly proliferate. This forms a new generation of antibody-producing plasma cells. This means that the antibody response is much more rapid and specific in subsequent infections than in primary infection, reducing the chance of symptom development. This is the principle behind vaccination.

158.(d) : Influenza A virus subtype H5N1, also known as A (H5N1) or H5N1, is a subtype of the influenza A virus that can cause illness in humans and many other animal species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for "highly pathogenic avian influenza virus of type A of subtype H5N1", is the causative agent of H5N1 flu, commonly known as "avian influenza" or "bird flu". It is endemic in many bird populations, especially in Southeast Asia. One strain of HPAI A(H5N1) is spreading globally after first appearing in Asia. It is epizootic (an epidemic in nonhumans) and panzootic (affecting animals of many species, specially over a wide area), killing tens of millions of birds and spurring the culling of hundreds of millions of others to stem its spread. HPA1A(H5N1) is an avian disease. H5N1 is mainly spread by domestic poultry, both through the movements of infected birds and poultry product and through the use of infected poultry manure as fertiliser or feed. Humans with H5N1 have typically caught it from chickens, which were in turn infected by other poultry or waterfowl. Migrating waterfowl (wild ducks, geese and swans) carry H5N1, often without themselves becoming sick. Many species of birds and mammals can be infected with HPAI A (H5N1), but the role of animals other than poultry and waterfowl as disease-spreading hosts is unknown.

(a) : The degree of pathogenicity of a microorganism is called virulence. This is indicated by case fatality rates and/or its ability to invade the tissues of the host; the competence of any infectious agent to produce pathological effects.

(a) : Hepatitis A caused by picornavirus a positive stranded RNA virus Hepatitis B - caused by partially double stranded, and partially single stranded DNA virus called Hydra virus.

(b): Cocaine is a natural alkaloid obtained from leaves of Erthyroxylon coca. Its chemical formula is C₁₇H₂₁ NO₄. It is a powerful CNS stimulant. It causes lack of sleep and loss of appetite.

Escherichia coli is the non-pathogenic bacteria of colon. One of the characteristics of Escherichia coli is the production of bacteriocins (colerains), a specific type of metabolite which is not only lethal to the organism of the same species but also to related organisms. Balantidium coli results in inflammation of alimentary tract. Entamoeba coli causes amoebic dysentery. Enterobius vermicularis infection is known as oxyuriasis or enterobiosis.

(d)

(a) In Entamoeba histolytica, the precystic or minute forms encyst only in the lumen of the intestine. In precystic stage, the chromatid bodies are found which disappear as the cysts mature.

(d): Wuchereria bancrofti is a dreaded human parasite. It is digenetic parasite completing its life cycle in two hosts, the final host is man harbouring the adult worm. The adult worms live coiled up in the gland and lymph vessels of man.