Natural infection of Lutzomyia spp. with Leishmania was studied with the aid of the polymerase chain reaction (PCR) in Chaute, Lima, Perú, a locality endemic for Andean cutaneous leishmaniasis (uta). The PCR, with primers specific for the L. braziliensis complex, was applied to sandfly pools. Sandflies were sampled from April 1990 to May 1991 with CDC light traps in homes, and from near homes with a Shannon trap using protected human bait. Lu. verrucarum (4 pools) and Lu. peruenis (2 pools) from the anthropophilic collections, and Lu. verrucarum (2 pools) from indoors were found to be infected with Leishmania. The majority of infected sandflies were recorded mainly in April 1991 (4 pools), coinciding with the highest sandfly densities and the maximum number of new cases of uta (7). Non-infected sandflies were found from May to October 1990 and January to March 1991. Thus, these 2 sandfly species play a role in the spread of leishmaniasis among humans and other animals in Chaute.

Evidence that domestic dogs may act as reservoir hosts for cutaneous leishmaniasis in the Peruvian Andes is provided by the isolation, for the first time, from naturally infected dogs of parasites identified (by isoenzymes) as Leishmania peruviana. Leishmania parasites were isolated from nasal aspirates or biopsies from 5 (1.8%) of 279 asymptomatic dogs samples in endemic villages of the Peruvian Andes. In addition, Leishmania (Viannia) infections were identified in 15 (5.4%) of 276 nasal samples by the polymerase chain reaction (PCR) using subgenus-specific primers. Further circumstantial evidence for a reservoir role for dogs comes from the finding of a relatively high dog blood index among the sandfly vectors collected inside houses (29% for Lutzomyia peruensis and 17% for Lu. verrucarum). Possible wild mammal reservoir hosts for Andean cutaneous leishmaniasis were also detected in endemic villages. At least 8 species were identified among the 1266 small mammals trapped. Leishmania parasites were isolated from blood or skin biopsies taken from 2 (2.6%) of 78 Didelphis albiventris and 6 (1.2%) of 511 Phyllotis andinum. Three isolates were identified by isoenzymes as L. peruviana, and the other 5 were identified by PCR as Leishmania (Viannia) species. Leishmania (Viannia) infections were also identified by PCR directly on skin biopsies taken from 2 (2.8%) of 72 D. albiventris, 1 (0.2%) of 499 P. andinum, and 4 (2.6%) of 153 Akodon sp.

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