The end of lymphatic filariasis?

When the British physician Patrick Manson incriminated mosquitoes as vectors of Wuchereria bancrofti in China in 1877, it was the first time that an insect had been associated with the active transmission of an agent of any human or animal disease. The minute filarial worms (microfilariae), were, however, first observed as blood parasites by another British physician, Timothy Lewis. A BMJ report in 1870 records he had noticed microfilariae in the urine of patients.1 Manson had read Lewis’s work and postulated that the worms lived in the lymphatic system, and that like other similar parasites, the females produced larvae viviparously. His curiosity about the fate of the microfilariae led to the discovery that they were transmitted by mosquitoes.

Lymphatic filariasis is a major cause of acute and chronic morbidity of humans in tropical and subtropical areas of Asia, Africa, the western Pacific, and some parts of the Americas. Over 20% of the world’s population live in areas where they are at risk of infection with filarial parasites. An estimated 120 million people are infected in at least 83 endemic countries, with 91% of cases caused by W bancrofti and the remainder by Brugia malayi and B timori.2

Uniquely among vector borne infections, lymphatic filariasis can be transmitted by five genera of mosquito (Anopheles, Aedes, Culex, Mansonia, and Ochlerotatus). Human infection occurs when the third stage (L3) infective larvae escape from the mosquito’s proboscis on to the skin and penetrate at the site of the bite. The larvae migrate to the lymphatic system, where they mature into adult male and female worms. As Manson suspected, adult …