[Epidemiology of cutaneous leishmaniasis in Bolivia. 2. Transmission patterns].

In Bolivia the transmission of tegumentary leishmaniasis due to Leishmania (V.) braziliensis depends both on environmental factors and human activities. In the Yungas, transmission takes place in the houses during the night. The vector is Lutzomyia nuneztovari anglesi Le Pont & Desjeux, which enters the houses after 10 p.m. and leaves them before 6 a.m. This transmission pattern explains why men and women are equally infected, generally before 10 years old. Some more adults are infected very likely in coffee plantations or in the relict forest where the same vector species abounds and bites in daytime. In the Alto Beni, pioneers, mainly males, are infected when clearing the forest. Three Psychodopygus species have been shown to be the vectors. The risk is drastically decreasing when people establish in plantations or nearby villages because sandfly vectors do not get easily out of the forest cover. In the Pando, forest people are infected when harvesting Brazil-nuts or bleeding the rubber-trees, the two main activities in the area. It is very likely that Ps. c. carrerai is one of the vectors. Pando and Alto Beni primary rain-forests are natural primary foci of Le. braziliensis. So far the mammalian reservoirs are unknown but the circulation of the parasite has been proven by the fast contamination of receptive people entering the forest. The Yungas primary forest may be also considered as a relict focus. The cultivated area of the Yungas is an anthropic secondary focus. The vector Lu. n. anglesi became adapted to coffee plantations from which it enters the houses and transmits the parasite to man.