Lymphatic filariasis is due to filarial parasites which are transmitted to humans through mosquitoes.
When a mosquito with infective stage larvae bites a person, the parasites are deposited on the person's skin from where they enter the body. The larvae then migrate to the lymphatic vessels where they develop into adult worms in the human lymphatic system. Infection is usually acquired in childhood, but the painful and profoundly disfiguring visible manifestations of the disease occur later in life. Whereas acute episodes of the disease cause temporary disability, lymphatic filariasis (LF) leads to permanent disability.
LF is endemic in 83 countries and there are an estimated 120 million cases, including 25 million men with hydroceles and 15 million people, primarily women, with lymphedema. The disease occurs throughout the tropical areas of Africa, Asia, the Americas and the Pacific, with around 66% of the infection clustered in South-East Asia and most of the remaining infection (~33%) centred in Africa.
LF is caused by a species of filarial round worms, or nematodes, with up to 90% of all infections caused by Wuchereria bancrofti. In some parts of Asia, LF is caused by Brugia malayi and Brugia timori. Various mosquito species transmit these worms: Culex mosquitoes transmit W. bancrofti in urban and semi-urban areas, Anopheles mosquitoes transmit worms in rural environments, especially in Africa, and Aedes mosquitoes are responsible for transmission throughout the Pacific.
To learn more about the transmission dynamics of lymphatic filariasis, please visit the Global Atlas of Helminth Infections (GAHI).
Numerous countries have implemented LF control programmes, with significant achievements in the Americas, the Pacific and Asia. A few countries in Africa are close to their elimination goals. To learn more about LF elimination, please visit the Global Atlas of Helminth Infections.