Immunoepidemiology of lymphatic filariasis: the relationship between infection and disease

Lymphatic filariasis is manifested by a spectrum of symptoms that range from microfilaraemia to gross immunopathology. The geographical variations seen in this disease have been explained by heterogeneity in genetically determined host responses. By modelling the disease through time, Don Bundy, Bryan Grenfell and P.K. Rajagopalan can provide a simple, unified explanation for the observed heterogeneity. Their model shows that there is a sequential progression from infection, microfilaraemia, amicrofilaraemia to obstructive disease in all individuals who experience microfilaraemia. Only the probability of developing microfilaraemia is geographically variable, being dependent on the local incidence of infection.