RESUMO

Trypanosoma cruzi, the cause agent of Chagas disease, is transmitted mainly by blood-feeding insects of the subfamily Triatominae. The T. cruzi life cycle alternates between triatomines and mammalian hosts, excluding birds and reptiles. Triatomines of Mepraia genus are wild vectors of T. cruzi in Chile. Mepraia specimens infected with T. cruzi have been detected in Pan de Azúcar and Santa María islands. The most common vertebrates that inhabit these islands are birds and reptiles, and it is unknown whether small mammals are present. Consequently, it is relevant to know whether there are any T. cruzi-infected small mammals on those islands to elucidate the T. cruzi cycle. To clarify this crossroads, islands of northern Chile were explored to determine if T. cruzi-infected triatomines and rodents co-occur in islands of northern Chile. T. cruzi DNA was detected by conventional and real-time PCR in three islands: on Santa María and Pan de Azúcar islands T. cruzi was detected in Mepraia sp samples, while on Pan de Azúcar (6.1%) and Damas islands (15%) was detected in the rodent Abrothrix olivacea. We show for the first time in Chile the occurrence of insular rodents infected with T. cruzi, and a complete T. cruzi life cycle in a coastal island. Our results provide new insights to understand the T. cruzi infection in the wild cycle.

RESUMO

Chagas disease is one of the main zoonoses mediated by vectors in America. The etiological agent is the protozoan Trypanosoma cruzi, transmitted mainly by hematophagous insects of the subfamily Triatominae. Mepraia species are triatomines endemic to Chile that play an important role in T. cruzi transmission in the wild cycle and are potential vectors for humans. In addition to the continental distribution, populations of Mepraia genus have been reported inhabiting islands of northern Chile. The presence of individuals of Mepraia in insular areas might be explained through passive dispersion by marine birds or by vicariance of an ancestral widespread population. To clarify the biogeographic origin and phylogenetic relationships of island individuals of Mepraia, mitochondrial COI and cyt b genes were sequenced in individuals from island and continental areas. Gene sequences were used to estimate phylogenetic relationships, divergence dates and migration rates between insular and continental populations. The dates of divergence estimates are congruent with sea level and tectonic changes that originated the islands during Pleistocene. Migration rates suggest symmetric historical island-continent gene flow. We suggest that the origin of island triatomines can be explained by both vicariance and dispersion. Phylogenetic relationships show that individuals from Santa María Island and the continent clustered in a clade different from those previously reported, indicating a new lineage of Mepraia genus. This study will contribute to understand the origin of the T. cruzi infection in coastal islands of northern Chile.

Assuntos

RESUMO

Chagas disease is one of the main zoonosis mediated by vectors in America. The etiologic agent Trypanosoma cruzi infects different mammals and is transmitted principally by the subfamily Triatominae. Mepraia is a genus endemic to Chile, responsible for transmitting T. cruzi in the sylvatic cycle. Mepraia includes three species: M. gajardoi and M. parapatrica inhabit coastal areas, while M. spinolai inhabits coastal and interior valleys. Previous studies reported the occurrence of Mepraia in Pan de Azucar Island, currently classified as M. parapatrica, but T. cruzi has not been reported in these insects. It is suggested that this could be due to infrequent insect feeding on mammalian hosts. In order to detect T. cruzi in insects from coastal islands, specimens from Pan de Azucar and Santa Maria Islands were examined. A region of kDNA of T. cruzi was amplified by PCR and hybridization assays were performed for T. cruzi genotyping of insect feces. The presence of infected insect and mixed T. cruzi infections was demonstrated. This is the first report of infected Triatominae in coastal islands in Chile. We discuss T. cruzi detection in insular zones, and the presumptive reservoirs that may participate in maintaining its transmission cycle in this habitat. Mixed and unidentified infections suggest that there are complex and unknown reservoir interactions in these habitats.

Assuntos