Question

Infective stage of Trypanosoma gambiense is
A. Metacyclic trypomastigote
B. Sporocysts
C. Sporozoite
D. Trophozoite

Answer 1

Hint: There are two species of African trypanosomiasis (also called sleeping sickness); each is named for the region of Africa in which they were found. The East African trypanosomiasis is caused by Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense is responsible for west African trypanosomiasis. Both these types are transmitted by the tsetse fly which is native to Africa.

Complete answer:
• The infection of this disease occurs in two stages:
• The first stage includes the invasion of the parasites in the blood and lymphatic system.
• The second stage involves the movement of the parasites inside the central nervous system.
• East African trypanosomiasis is more acute than West African trypanosomiasis as it progresses to the second phase within a few weeks.
• Fever, severe headaches, extreme fatigue, swollen lymph nodes, and painful muscles and joints are common symptoms of sleeping sickness.
• Some people often develop a rash on their skin.
• During the second stage the following symptoms occur-progressive confusion, personality changes, and other neurologic problems that occur after the infection has invaded the central nervous system. If left untreated, death will occur within months.
• Trypanosoma gambiense is transmitted by tsetse flies. The fly vector contains the parasite and undergoes transformations that prepare it to infect the human host.
• These developmental stages are the replicative procyclic and epimastigote forms and the non-replicative, infective, metacyclic form that develops in the salivary glands of the fly.

Hence, the correct answer is option (A).

Additional information:
Both the male and female flies can transmit the infection. Other modes of transmission are possible. A pregnant woman can also pass the infection to her unborn baby sometimes. It is also estimated that the infection can also be transmitted by blood transfusion, organ transplantation, and laboratory exposure, but such cases have no proper evidence.

Note: The complete development takes place on fly and lasts about 20 days. The infective stage happens in salivary glands. There they undergo the transformation and the product formed is a somewhat short and stumpy infective stage. Then after becoming infected, they are passed onto humans through biting and infection occurs.