This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Transfusion-associated malaria has a shoer incubation period because of the presence in blood of: 
Select and explain. 
A. Trophozoites, B. Sporozoites, C. Female gametocyte, D. Merozoites
A: Trophozoites
Answer: A: Trophozoites 
Explanation: Ans: A. Trophozoites(Ref: Paniker's 7/e p77, 6/e p69; Harrison 19/e p1374)Transfusion associated malaria has a shoer incubation period because of presence of trophozoites in blood.Malaria can be transmitted by blood transfusion, needle-stick injury, sharing of needles by infected injection drug users, or organ transplantation.The incubation period in these settings is often sho because there is no pre-erythrocytic stage of development.Parasites may remain ble in blood bank for 1-2 weeks.As this condition is induced by direct infection of red cells by the merozoites, pre-erythrocytic schizogony and hypnozoits are absent.Relapse does not occur and incubation period is sho.