Filariases

It is apparent that there are many similarities among the various filariae. Besides a common life cycle, with an arthropod vector and human hosts, there are similarities in the diseases that they produce. This clinical picture takes one of two main courses: (1) characteristic disease produced by the presence of adult nematodes in their target tissue, which distinguishes typical cases for each of the filariae, and (2) the systemic hypersensitivity reactions to the circulating microfilaria, which tend to be similar. The characteristic feature of Wuchereria bancrofti is genital disease with funiculitis and hydrocele and less often elephantiasis. For Brugia malayi it is elephantiasis of the distal leg or arm, usually leaving the knee or elbow uninvolved with normal contours. Brugia timori, restricted to just a few islands of Indonesia, produces elephantiasis similar to that of Brugia malayi, but with its characteristic descending lymphadenitis. Loa loa is best known for the Calabar swelling, or angioedema, that it produces, although other filariae can induce similar reactions. Both Loa loa and Dirofilaria tenuis cause macroscopic, subconjunctival eyeworms. Clinical disease from onchocerciasis takes four predominant forms: eye disease, lymphadenitis, subcutaneous nodules (onchocercomata), and a pruritic, hypopigmented, or hyperpigmented papular dermatitis.