Question

In cases of filariasis, samples for microscopic detection of microfilariae are taken at night because

• A. Since the disease is spread by mosquitoes, it is best to take the sample at night
• B. The larvae circulate in the bloodstream of patients only at night
• C. Microfilariae circulate in the capillaries in the superficial parts of the body only during the night
• D. Microfilariae reproduce during the night and hence, larger numbers can be found in one sample

Answer 1

The correct option is C Microfilariae circulate in the capillaries in the superficial parts of the body only during the night

Wuchereria bancrofti is a filarial nematode that, as an adult, is a thread-like worm. Adult worms reside in the lymph nodes where the female parasite reproduces to form larvae, while the larvae called microfilariae circulate in the bloodstream. During daytime the microfilariae move through the blood vessels deep inside the body and during the night, they move to the superficial parts, which are the capillaries in the skin. The standard test for detecting the infection is microscopic examination of a blood smear for the presence of the microfilariae. The blood should be sampled at night as that is when the larvae circulate in the superficial parts of the body.