FREQUENCY-DISTRIBUTION OF WUCHERERIA-BANCROFTI INFECTION IN THE VECTOR HOST IN RELATION TO HUMAN HOST - EVIDENCE FOR DENSITY-DEPENDENCE

This paper uses detailed entomological data from Pondicherry to compar e the microfilaria distribution in vector with that of human and also to examine the evidence for the operation of density dependence on par asite transmission. Analysis showed that the distribution in vector is similar to that in human. The expected distribution derived from the fit of a zero-truncated negative binomial to the human data, closely r eflected the observed microfilaria distribution in the vector. This im plies that a relatively large proportion of observed microfilaria nega tives in the vector population may be true zeros, as observed in human , arising from the biting on true negatives (as yet uninfected, with u nmated female worms or immune) in humans, rather than attributable to the blood sampling process. Further it was found that both the prevale nce of infection and the degree of parasite aggregation in the vector population falls significantly with parasite stage, implying the opera tion of density dependence, perhaps via parasite-induced vector mortal ity.