Trypanosome and leishmania infection in sloths (Choloepus hoffmanni and Bradypus variegatus) in Panama

Two-toed (Choloepus hoffmanni) and three-toed (Bradypus variegatus) sloths are commonly found across undisturbed and fragmented Neotropical forest landscapes. Two and three-toed sloths harbor a wide range of viruses and... [ view full abstract ]

Two-toed (Choloepus hoffmanni) and three-toed (Bradypus variegatus) sloths are commonly found across undisturbed and fragmented Neotropical forest landscapes. Two and three-toed sloths harbor a wide range of viruses and protozoan parasites, including those causing vector-borne zoonoses, such as Leishmania spp. parasites. Although in Panama sloths are common blood meals for Rhodnius pallescens, the principal local vector of Trypanosoma cruzi, the Chagas disease agent, the role of sloths in trypanosome transmission is poorly understood. The objective of this study was to evaluate trypanosome (T. cruzi and T. rangeli) and leishmania infection prevalence in sloths from a fragmented forest landscape. The competence of sloths in the trypanosome transmission cycle was evaluated by xenodiagnosis. In 3 sites in fragmented forest landscapes west of the Panama Canal, 66 sloths (N=15 Bradypus variegatus and N=51 Choloepus hoffmanni) were captured, immobilized, examined, blood was taken, and xenodiagnostic studies were performed using using 10 nymphs (4th or 5th instars) of uninfected R. pallescens. Leishmania spp. Were identified by kDNA PCR and PCR-RFLP of the hsp-70 gene. Duplex PCR and culture were used to evaluate single and co-infections with T. cruzi and T. rangeli. Overall, Leishmania spp. were detected in 54% of sloths (36/66) and 32% (21/66) of sloths were positive for trypanosomes by duplex PCR; 1.5% (N=1) T. cruzi, 27.3% (N=18) T. rangeli, and 3% (N=2) T. cruzi-T. rangel co-infection. Of 29 sloths tested by xenodiagnosis, 13 were positive for T. rangeli, 3 were positive for T. cruzi, and 13 were negative. Results suggest that sloths are highly competent reservoirs for T. rangeli, but less likely to transmit T. cruzi to vectors, echoing historical studies before the molecular diagnostic era. Behavior, life history traits, and vector-host interactions may explain why sloths are unlikely to be highly competent reservoirs for T. cruzi, yet important reservoirs for Leishmania spp.