Wuchereria bancrofti is digenetic, i.e., its life history is completed in two hosts; man is the
main host, while female mosquito, usually Culex pipiens, is the secondary host.
Mature male and female worms copulate in the lymph glands of man where they usually
live. Since female worm is viviparous or ovoviviparous, it delivers numerous larvae called
microfilariae. The microfilariae are born in very immature stage. However, microfilariae
find their way into the blood stream where they can live for a considerable time without
undergoing any developmental changes. Microfilariae exhibit nocturnal periodicity, as they
appear in peripheral circulation of skin periodically at night only generally between 10 pm
and 4 am, but during daytime they are confined inside the deeper large blood vessels. In
fact, the nocturnal periodicityf n.icrofilariae is said to be related with the nocturnal feeding
habit of their secondary host, Culex.
When microfilariae are sucked up by the secondary host, they immediately enter in the
stomach of mosquito, the sheaths around their bodies are shed off and then they penetrate
the gut wall within an hour or two and migrate to the thoracic muscles. Here they become
short and thick like sausages within 2 days having short spiky tails and measure 124 to