In 2015, emergent cases of localized cutaneous leishmaniasis (LCL) were reported in Tinum, Yucatan, Mexico. As part of an eco-epidemiological study to characterize the elements that trigger Leishmania infection in that area, we conducted a field study to investigate the occurrence of Leishmania infection in wild rodents. From November 2019 to February 2020, rodents were caught from three sites located in the municipality of Tinum, Yucatan. For each specimen, clinical signs suggestive of Leishmania infection were recorded. Samples from the tail, liver, and spleen were taken for the identification of Leishmania DNA by PCR. Twenty rodents belonging to two species were caught including Heteromys gaumeri (55, 11/20) and Ototylomys phyllotis (45, 9/20). Fifty-five percent of the animals presented white spots on the tail, 15 had splenomegaly, and 5 had hepatomegaly. Fifty-five percent (11/20) of the animals were found infected by Leishmania. Heteromys gaumeri was caught in all trapping sites and was the most infected species (63.6, 7/11). The percentage of infection for O. phyllotis was 44.4 (4/9). Leishmania (Leishmania) mexicana was identified as the infecting species in two H. gaumeri. This study provides, for the first time, evidence of Leishmania infection in wild rodents from the Yucatan state. Heteromys gaumeri and O. phyllotis may be involved in the transmission cycle of L. mexicana in this emergent focus; however, further longitudinal studies are needed to confirm their role as primary reservoirs.

Objetivo. Determinar la presencia de Rickettsia typhi en roedores sinantrópicos capturados en la comunidad rural de Bolmay, Yucatán, México, con antecedentes de tifo murino en sus habitantes. Materiales y métodos. Se examinaron 37 roedores: 30 Mus musculus, 6 Rattus rattus y 1 Heteromys gaumeri. Se obtuvo ADN total del bazo de los roedores. La identificación de R. typhi se realizó a través de la amplificación de un fragmento del gen htrA (proteína 17-kDa) por PCR punto final. Los productos positivos fueron purificados y enviados a secuenciación para su análisis de alineamiento con la herramienta BLAST. Resultados. La identificación de ADN rickettsial se logró en un 27% (10/37) de los roedores: siete M. musculus y 3 R. rattus. El análisis de alineamiento obtuvo porcentajes de identidades y coberturas del 97 - 99% para R. typhi, respectivamente. Conclusiones. El presente estudio sugiere la participación de los roedores sinantrópicos en el ciclo de transmisión del tifo murino en la región. Se describe la primera evidencia molecular de R. typhi en M. musculus de Yucatán, México.

Asymptomatic infection (the absence or inapparent signs and symptoms) has been observed in many endemic areas of leishmaniasis, however, little is known about the parasitological and immunological factors associated with this type of infection. This study aimed to identify the in vitro expression of IFN-γ in asymptomatic carriers of viable Leishmania parasites. Asymptomatic infection was identified using the Montenegro skin test in an at-risk population from Yucatan, Mexico. Parasite viability was evinced in the blood by 7SL RNA transcripts amplification. The expression of mRNA IFN-γ was analyzed in peripheral blood mononuclear cells stimulated with soluble Leishmania antigen, using RT-qPCR. Parasite viability was observed in 33.3 % (5/15) of asymptomatic subjects. No differences were found in the expression of IFN-γ between asymptomatic and healthy subjects, and no correlation was found between the presence of viable parasites and the expression of IFN-γ. This study demonstrates the persistence of Leishmania parasites in the absence of an in vitro IFN-γ response in asymptomatic carriers from Mexico.