Environmental factors and the distribution of mansonelliases in southern Venezuela

The distribution of mansonelliases and their relation to various quantitati ve criteria were determined through the study of 1,057 subjects in 17 local ities in ten regions of Amazonas State and Bolivar State. The total prevale nce among the blood samples, determined through the Knott technique, was 18 .54 %. 11.26 % were parasited by Monsonella perstans, 9.93 % by Mansonella ozzardi, and 2.63 % by both species. The average of microfilaremia was 48.1 9 mf/mL of blood in M. perstans and 13.79 mf/mL in M. ozzardi. In the regio ns studied, M. ozzardi has a wider area of distribution than M. perstans. P revalence, average number of parasites per host, and the infection index ha ve a positive and statistically significant correlation with the total annu al precipitation mean for each region for M. perstans; in the case of M. oz zardi the quantitative parameters ore positively correlated with the altitu de of each region, this correlation being statistically significant. With r espect to type of vegetation, M. perstans had a higher infection index in A mazonian caatinga transition in pluvial lowland forest, and M. ozzardi in s emideciduous forest of the alisio type. Therefore two types of transmission , M. ozzardi-Simulium and M. perstans-Culicoides are suggested.