Question

The causative agent of the disease ‘sleeping sickness’ in human being is an
A) Intracellular parasite found in RBC.
B) Extracellular parasite found in blood plasma.
C) Intracellular parasite found in WBC.
D) Extracellular parasites found on the surfaces of platelets.

Answer 1

Hint: In this question we are going to find the causative agent of the disease sleeping sickness in human being.Human African trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease. It is caused by infection with protozoan parasites belonging to the genus Trypanosoma.

Complete answer:
Let's discuss the above option and find out the correct answer.
A) Intracellular parasite found in RBC:-the parasite can be found in the bloodstream of infected people; and the parasite might be spread to other people through exposure to an infected person's blood (for example, by blood transfusion or by sharing needles or syringes contaminated with blood).Examples of parasitic diseases that can be bloodborne include malaria ,toxoplasmosis etc. hence option A is incorrect.
B)Extracellular parasites found in blood plasma:-Parasites have complex life cycles, alternating between different hosts and facing multiple hostile environments. Trypanosomes is the causative agent for sleeping sickness. This parasite is present in the blood plasma. When the fly bites the host, the metacyclic trypomastigotes enter the blood and from the trypomastigotes. These increase in number and can cross the blood brain barrier and affect the brain. Hence option B is correct.
C)Intracellular parasite found in WBC.Leukopenia may confound population studies that estimate parasite densities on the basis of an assumed WBC count of 8000 cells/μL.C Hence option C is incorrect.
D)Extracellular parasite found on the surfaces of platelets:although there is a broad sense that platelets are proinflammatory and initiate or accelerate immune cell responses to infection in general, some reports have indicated a potential direct anti-Plasmodium parasite-killing role for platelets. Hence option D is incorrect.

Hence option ‘B Extracellular parasite found in blood plasma is the correct answer.

Note:Fever, severe headaches, irritability, extreme fatigue, swollen lymph nodes, and aching muscles and joints are common symptoms of sleeping sickness. Some people develop a skin rash.