Small mammals as hosts of Leishmania spp. in a highly endemic area for zoonotic leishmaniasis in North-Eastern Brazil.

Background: Leishmania parasites cause leishmaniasis in humans and animals worldwide. These parasites are transmitted by phlebotomine sand flies, which become infected upon feeding on an infected mammalian host. We assessed the occurrence of Leishmania infection in small mammals in an area of cutaneous and visceral leishmaniasis endemicity.
Methods: A total of 180 small mammals were trapped in 2003 and 2006 in a rural area in north-eastern Brazil. Spleen and skin samples from these animals were assessed by two PCR protocols, one targeting Leishmania (Viannia) spp. and other Leishmania (Leishmania) infantum. Additionally, serum samples were tested by an immunochromatographic test with rK39 as antigen.
Results: Overall, 23.2% (38/164) of the animals were positive to L. (V.) spp. and 8.8% (14/160) to L. (L.) infantum). Five animals of four species (Didelphis albiventris, Nectomys squamipes, Rattus rattus and Holochilus sciureus) were positive by both PCR protocols, an overall co-infection rate of 2.5%. By serology, 5% (7/139) of the animals were positive, but all of them were PCR-negative. An isolate obtained from a water rat (N. squamipes) was characterized as L. (V.) braziliensis (zymodeme Z-74).
Conclusions: This study reinforces the involvement of different small mammals (e.g., N. squamipes, R. rattus and H. scieurus) in the transmission cycles of L. (V.) braziliensis and L. (L.) infantum in north-eastern Brazil. The finding of L. (V.) braziliensis infection in black rats suggests a rapid process of adaptation of a New World Leishmania species to an Old World rodent and raises interesting questions regarding the co-evolution of these parasites and their vertebrate hosts.