Filariasis

Filariasis refers to a group of parasitic infections caused by thread-like nematodes transmitted to humans through insect vectors such as mosquitoes, blackflies, and deerflies. Only a few of the hundreds of known filarial species naturally infect humans.

The primary clinical forms include lymphatic filariasis, onchocerciasis, loiasis, and mansonelliasis. Lymphatic filariasis, caused by Wuchereria bancrofti, Brugia malayi, or Brugia timori, is the most widespread and is recognized by the World Health Organization as a leading cause of disability worldwide.

The 5 species of nematodes of the family Filarioidea responsible for disease in man are:

• Wuchereria bancrofti - mosquito: Culex, Aedes, Anopheles
• Brugia malayi - mosquito
• Brudia timori - mosquito
• Loa loa - deerfly: Chrysops
• Onchocerca volvulus - blackfly: Simulium

These nematodes require two hosts to complete their life cycle, and following infection and development of the adult worm in a human host, the female worm releases larval microfilariae. These are then spread by insect vectors.

Diagnosis relies on clinical assessment supported by laboratory testing, such as antigen assays, blood smears, or skin snips.

Management includes antiparasitic medications, hygiene-based interventions, vector control, and, in selected cases, surgery. Prevention is achieved through personal protective measures and mass drug administration in endemic regions.

Reference

1. Local Burden of Disease 2019 Neglected Tropical Diseases Collaborators. The global distribution of lymphatic filariasis, 2000-18: a geospatial analysis. Lancet Glob Health. 2020 Sep;8(9):e1186-94.