Natural infection of wild capybaras (Hydrochoerus hydrochaeris) with novel Anaplasma spp. and Ehrlichia spp.

MONJE, L.D.; BELDOMENICO, P.M.; EBERHARDT, A. T.; RUIZ, M. F.

Kuala Lumpur

Congreso; 19TH Internacional Congress of Infectious Diseases.; 2020

The International Society for Infectious Diseases (ISID)

Background: Anaplasma and Ehrlichia (Rickettsiales: Anaplasmataceae) are intracellular Gram-negative bacteria of medical and veterinary importance that infect monocytes, neutrophils, endothelial cells or platelets, depending upon the species involved.The capybara, Hydrochoerus hydrochaeris, is a large rodent found in tropical to temperate freshwater wetlands of South America, considered to be the most important amplifying host of the human pathogen Rickettsia rickettsii (Rickettsiales: Rickettsiaceae). In Esteros del Iberá (northeastern Argentina), capybaras are present at high densities, living close to farms and urban settlements, resulting in an extensive human-livetock-wildlife interface that may represent a potential risk to public health.Methods & Materials: We investigated the potential role played by capybaras and their ticks on the ecology of Anaplasma spp. and Ehrlichia spp. in northeastern Argentina. During 2010?2016 blood samples from 70 capybaras and more than 9400 Amblyomma dubitatum questing ticks were obtained from a ranch in Esteros del Iberá (28°36′ S 57°49′ W). Ticks were identified by using standard taxonomic keys. DNA was extracted from blood and ticks and all samples were screened for Anaplasmataceae by a real-time PCR assay targeting the 16S rRNA gene.Results: Prevalence of Anaplasma spp. infection in capybaras was high (50.0%), while Ehrlichia spp. prevalence was lower (12.8%). Interestingly, very low prevalence of both Anaplasma (0.03%) and Ehrlichia (0.07%) was observed in questing ticks. Molecular analysis using 16S rRNA gene showed that Anaplasma sp. from capybaras was closely related to Anaplasma odocoilei from North America, while Ehrlichia sp. was related to Candidatus Ehrlichia khabarensis from Eastern Russia. In addition, we observed Anaplasma sp. infecting capybaras platelets, which coincides with the tropism of A. odocoilei in deer.Conclusion: Our results showed the presence of novel rickettsial agents infecting a population of free-ranging capybaras in northeastern Argentina. The extremely low prevalence of these agents in capybara´s ticks (Amblyomma dubitatum) excludes this arthropod as a competent vector, warranting further research to find the possible vectors of these bacteria.