Which one of the following life cycle stages of Wuchereria bancrofti is infective to man?

• Microfilaria

• 1^st stage larva

• 2^nd stage larva

• 3^rd stage larva

D.

3^rd stage larva

Wuchereria or filarial worm is a diagenetic parasite. Its primary host is human and Culex mosquito is the intermediate host. When a mosquito bites an infected person, microfilarial or first stage juvenile are picked up. Inside the mosquito muscles, microfilariae transform into infectious parasite or third stage juvenile which are deposited near the site of mosquito. When this mosquito bites a healthy person, third stage juvenile or infectious parasite penetrates through the punctured skin and reach the human lymphatic system.