Filariasis is a parasitic disease caused by filarial parasites in the human body. There are eight known species of parasitic filarial worms in the human body, with Bancroftian and Malayan filarial worms mainly prevalent in China. To the north of the Yangtze River, B. bancrofti is the main parasite, while to the south of the Yangtze River, both species are present.
The early manifestations are lymphadenitis and lymphangitis, and in the late stages it can develop into lymphoedema, elephantiasis and sphingomyelitis, which is a serious and debilitating disease.