A preliminary survey of the prevalence ofMansonella ozzardiin some rural communities on the river Purus, state of Amazonas, Brazil

Three hundred and eighty-six blood films were taken from mesticos (persons of mixed race) in villages on the river Purus, Amazonas; 17(4-4%) were infected with Mansonella ozzardi. An average of 11-2 microfilariae/20 mm3 of blood (range 1-103) were found in infected persons. No statistical difference was found between the infection rates of males and females. Seringueiros (rubber collectors) and lavradores (agricultural workers) showed similar high infection rates, compared to people with indoor occupations. Rubber-collecting communities showed a higher infection rate with M. ozzardi than villages economically dependent on the local municipal town. It is suggested that this was due to greater numbers of infective vectors in these locations, and to the higher proportion of the human population working outdoors.