Filariasis (Philariasis) is a parasitic tropical disease, caused by a thread-like parasitic worm of the type of nematode. Some of examples are Wuchereria bancrofti and Brugia malayi. These parasites are transmitted by mosquitoes.

The common presentation of filariasis is elephantiasis. It is the thickening of the skin and tissues due to the present of parasites in the lymphatic system. Elephantiasis mainly affects legs, but also can affect ears and mucus membranes. W. bancrofti can affect legs, arms, breats and vulve.

Life cycle
Life cycle of W. bancrofti (male – around 5cm, female – around 10 cm)
The human being serve as definitive host while the mosquitoes as intermediate hosts. Microfillaria would reside in the lymphatic circulation and constantly migrate between the deep (during the day) and peripheral circulation (at night). And the worm is transferred into a vector (mosquitoes). Inside the mosquitoes, they would mature into motile larvae and be ingested into the blood stream of another human. The larvae will then moves to the lymph nodes (mostly in the legs or genital area) and develop into an adult worm in a year.
Pathogenesis of W.bancrofti

After infection, the worms will mature in 6-8 months. There is an asymptomatic phase and then an inflammatory phase where the antigens of the worms cause inflammatory responses and disrupt the flow which causes lymphedema. There will be symptoms of fever, chills, skin infections, painful lymph nodes and tender skin of lymphedematous extremity. An obstructive phase after that marks the development of lymph varices, hydrocele and elephantiasis.
This disease is endemic in Asia, Africa, Central and South America. A diagnosis can be made by identifying the microfilariae on a Giemsa stained thick blood film. The blood is drawn at night when the parasites circulate. PCR can also be use as a tool for diagnosis.
Treatment
Albendazole, ivermectin and diethylcarbamazine. Doxycycline had been suggested to treat elephantiasis as well.