A COMPARATIVE FIELD-STUDY OF THE RELATIVE IMPORTANCE OF LUTZOMYIA-PERUENSIS AND LUTZOMYIA-VERRUCARUM AS VECTORS OF CUTANEOUS LEISHMANIASIS IN THE PERUVIAN ANDES

A two-year field study of Andean cutaneous leishmaniasis (uta) in the valley of Purisima, Ancash Department, Peru has provided quantitative epidemiologic and entomologic evidence for the predominant role of Lut zomyia peruensis in the transmission of Leishmania peruviana in this e ndemic area. The monthly incidence in the valley was greatest in the w et season (from December to May), when Lu. peruensis was particularly endophilic. A significant correlation was detected between intradomici liary (but not extra-domiciliary) Lu. peruensis abundance and the mont hly incidence of uta in the valley following a one-month time lag. In contrast, no significant correlation was detected between any measure of Lu. verrucarum abundance and the incidence of uta. Lutzomyia peruen sis and Lu. verrucarum comprise more than 98% of all the sand fly capt ures made in this valley. The increase in incidence of uta with altitu de, which reached a peak rate between 2,250 and 2,750 meters above sea level, was associated with an increase in the relative abundance of L u. peruensis as compared with Lu. verrucarum. Seasonal and altitudinal variation was also detected in the peak time of activity for both san d fly species, a phenomenon that could significantly influence the tra nsmission rate: later host-seeking sand flies being more likely to fin d sleeping, nondefensive, human hosts.