Classification: ICD-125.2; ICD-10 B74.3
Syndromes and synonyms: Loa loa filariasis, loiasis, African eyeworm, Calabar swelling
Agent: Filarial nematode (roundworm), Loa loa. Adult worms are nematodes that live freely in subcutaneous tissue. Adult females are 40–70 mm long and males are 30–34 mm long.
Reservoir: Humans. Loa loa also infects some monkeys but the human and simian cycles seem to be independent.
Vector: Tabanid adult female flies, mainly Chrysops silacea, C. dimidiata, and C. distinctipennis. These day-biting and blood-sucking flies breed in forested and damp environments (e.g. swamps or rotten vegetation). Other favorable environments are cocoa plantations. Chrysops are attracted by movement, dark objects, and smoke. The vector does not enter structures like homes or barns. Up to 18% of the vector population can be infected with L. loa in endemic areas.
Transmission: Infective larvae migrate out of the mouth part of the fly during bite onto the skin and subsequently enter the wound. The tabanid bite is painful with blood loss.
Cycle
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