Mosquito-borne infections in Fiji. 3. Filariasis in northern Fiji: epidemiological evidence regarding the mechanisms of pathogenesis.

During a filariasis survey conducted in northern Fiji in 1968-9 examinations were made for microfilaraemia, enlarged lymph nodes and elephantiasis. Analysis of the microfilarial densities at different ages and the number of anatomical sites showing lymph gland enlargement or elephantiasis have been used to provide evidence on the clustering of infections and pathogenesis.Although there is no evidence of clustering of risk of infection, there is evidence favouring the clustering of adult filariae in individuals. Nevertheless the number of sites of lymph node enlargement do not correspond with this finding and statistical evidence suggests that lymph-node enlargement is not necessarily associated with the near presence in the body of adult filariae, whether dead or alive.Males of Indian ethnic origin showed a higher prevalence of elephantiasis than males of Fijian ethnic origin, but women of either ethnic race showed prevalences lower than those of men.The onset of elephantiasis at a site does not directly reflect the number of infections sustained in the local area, but it appears that filariasis first induces for a limited period a proneness to elephantiasis. During this period a random and discrete event may induce the onset of elephantiasis. The nature of the event is unknown, but it probably is not trauma.