In: Biology
describe why Filarial parasites undergo nocturnal periodicity and what accounts for this phenomenon.
Answer: Filariasis is a parasitic infection caused by Wuchereria bancrofti (helminthiasis). The infection is spread by blood-feeding insects (black flies, mosquitoes etc.). In host peripheral blood circulation the peak of parasite in night when the mosquito vectors are seeking a blood meal. Numerous auto fluorescence granules are present in nocturnal species of W. Bancrofti. The present granules act as photoreceptors responsible for negative phototoxic of microfilariae. So in day time these negative photoreceptor gives the negative signal for their movement. However, when the host (infected individuals) keep for long time in dark (in day time) or the individual working in coal mining these photoreceptors are not active even in day time due to lack of exposed sunlight then the microfilariae move in peripheral circulation. So the presence of autofulorescence photoreceptor is responsible for the nocturnal activity of parasite W. Bancrofti.Normally for diagnosis the blood samples can be collected in night (when the parasite concentration is high in blood circulation) or by the use of Diethylcarbamazine (DEC) even in day time. DEC induce the circulation of microfilariae in peripheral blood circulation.