[Microfilarial loads of onchocerca and experimental vectorial capacity of Simulium soubrense-Simulium sanctipauli group in the forest zone of Ivory Coast].

Mass treatment programs using ivermectin are now beginning in forest areas and simuli will soon be feeding on individuals with low microfilarial loads (probably < 10). Most previous reports have involved higher mean loads (range: 14-6950. The purpose of this study was to ascertain the impact of low microfilarial loads on the number of infecting larvae present at the end of a parasite cycle in the Simulium soubrense-Simulium sanctipauli group and on availability for transmission to man by inoculation. Tests were carried out on five subjects from a forest area of southwest Ivory Coast who were infected with onchocerciasis and presented mean microfilarial loads of 1, 5, 10, 20, and 100. Findings showed a direct correlation between microfilarial load (1, 5, 20, and 100) and intake of microfilaria per dissected female. Similarly there was a correlation between microfilarial loads (1, 5, 10, 20, and 100), quantity of infected females, and number of infecting larvae per infected female. Parasite output was variable but decreased as microfilarial load increased. This study suggests that the experimental vectorial capacity of simuli is similar in subjects presenting onchocerciasis with high and low microfilarial loads.