Question

Student to attempt either option (A) or (B).
(A) Describe any two situations where a medical doctor would recommend injection of pre-formed antibodies (antitoxins) into the body of a patient. 
OR 
(B) The symptoms of malaria do not appear immediately after the entry of sporozoites into the human body when bitten by female Anopheles mosquito. Explain why it happens.

Hint:

Pre-formed antibodies (antitoxins) provide passive immunity for immediate protection, while malaria’s delayed symptoms are due to the parasite’s initial liver stage.

Answer 1

(A):
Step 1: One situation is when a patient is exposed to tetanus (e.g., through a deep puncture wound). A doctor injects tetanus antitoxins to neutralize the toxin produced by Clostridium tetani, providing immediate protection. 
Step 2: Another situation is in the case of snakebite (e.g., a venomous snake like a cobra). Antivenom (pre-formed antibodies) is injected to neutralize the snake venom, preventing systemic damage. 
OR 
(B): 
Step 1: Malaria symptoms do not appear immediately because the Plasmodium sporozoites injected by the Anopheles mosquito first travel to the liver, where they multiply into merozoites during the pre-erythrocytic stage (about 5–16 days). 
Step 2: Only after this incubation period do merozoites enter the bloodstream, infect red blood cells, and cause symptoms like fever and chills as they multiply and rupture the cells. 
Thus, (A) includes tetanus and snakebite scenarios, while (B) explains the delayed onset of malaria due to the parasite’s life cycle.