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In Colombia it has been suggested that the rodent Proechimys canicollis may be a reservoir-host of Leishmania (L.) chagasi, the cause of American visceral leishmaniasis, based on polymerase chain reaction/hybridization tests. We have detected no infection in laboratory-bred specimens of another species, P. guyannensis, after their inoculation with promastigotes or amastigotes of this parasite from Amazonian Brazil.

The population structure of strains of Leishmania (Viannia) braziliensis sensu lato from Pará State and Paraná State in Brazil, of L. (V.) shawi and L. (Leishmania) amazonensis from Pará State, and the relationships of type strains of the subgenera L. (Viannia) and L. (Leishmania) were examined by the random-amplified polymorphic deoxyribonucleic acid (RAPD) technique. Four different primers (M13-40, QG1, L15996 and delta gt11R) were used. The bands were analysed using the neighbor-joining (NJ) and unweighted pair-group method with arithmetic averages (UPGMA) algorithms of the MEGA package. The topology of the NJ and UPGMA trees was very similar but they were not always identical. Both trees differentiated the standard strains of the different species. Strains from the same location were grouped together only in the UPGMA phenogram of the M13-40 primer. L. (V.) braziliensis isolates from Paraná State were genetically closer to those from Paragominas, Pará State than to those from the Amazonian regions of Carajás in Pará State and Peru. The relationship was not dependent on geographical distance. It is postulated that the groups arose from different origins, in which the Amazonian stocks were related to Psychodopygus sand flies while the Paraná strains originated from a gene pool transmitted by Lutzomyia sand flies such as Lutzomyia (Nyssomyia) whitmani. Transmission by Ps. complexus in Paragominas is considered to be a secondary adaptation from the Lutzomyia leishmanial gene pool. Although the vectors of L. (V.) braziliensis are poorly known in the Amazon region, there is strong evidence that the major vectors are all Psychodopygus spp. There was a high degree of genetic variability amongst the L. (V.) shawi strains and there was no clear grouping according to the strains' origins. The genetic variability amongst L. (L.) amazonensis strains from the same locations was much lower but they formed 2 groups which coincided with their origin. Our results support the clonal population structure of Leishmania isolates and suggest that their distribution is related to the origin of the gene pool as well as to present vector and reservoir movements.

The clinical and epidemiological features of 62 cases of cutaneous leishmaniasis due to Leishmania (Leishmania) amazonensis, from Pará State, Amazonian Brazil, are discussed. The parasite, isolated in hamster skin and/or blood-agar culture medium, was in each case identified by both biological characteristics and a monoclonal antibody specific for promastigotes of L. (L.) amazonensis. Of the 62 patients, 46 (74.2%) presented with a single cutaneous lesion, and on no occasion was evidence found indicating metastatic spread to either the naso-pharyngeal mucosae or the viscera. Recent claims that this parasite may be responsible for both mucocutaneous leishmaniasis and typical visceral leishmaniasis are discussed. Meglumine antimoniate (Glucantime) proved highly efficient in the treatment of all patients. Of the 62 patients examined by the Montenegro skin test, only 32 (51.6%) gave a positive reaction. The significance of this finding is considered and the hypothesis made that the parasite itself may induce an immunoinhibition. Field studies amply confirmed the role of Lutzomyia flaviscutellata as the major sandfly vector of L. (L.) amazonensis in Amazonia.