Capybara (Hydrochoerus hydrochaeris) exposure to Rickettsia in the Federal District of Brazil, a non-endemic area for Brazilian spotted fever.

Ana Paula Nunes De Quadros,Thamiris Figueiredo Da Silva,Giane Regina Paludo,Paulo Sérgio Ribeiro De Mattos,Andréa De Moraes Carvalho,George Magno Sousa Do Rêgo,Thiago Fernandes Martins,Márcio Botelho De Castro,Marcelo Bahia Labruna,Lina De Campos Binder

doi:10.1590/s1984-29612021035

Abstract

In this study, whole blood samples and ticks were collected from 57 capybaras in recreational areas in the Federal District, Brazil, aiming to investigate the presence of Rickettsia spp. using polymerase chain reaction (PCR) and indirect immunofluorescence (IFAT) assays. None of the capybara blood samples yielded rickettsial DNA by PCR. Among 55 capybara serum samples tested by IFAT, 53 (96.3%) reacted to Rickettsia spp. Among these, 21 (39.6%) identified the R. bellii antigen as the probable antigen involved in a homologous reaction (PAIHR), whereas 2 (3.8%) identified the R. parkeri antigen. Ticks collected from capybaras were identified as 173 Amblyomma sculptum and 410 A. dubitatum, in addition to nine Amblyomma spp. larvae. A sample of 231 ticks was subjected to DNA extraction and PCR for Rickettsia species. None of 122 A. sculptum yielded rickettsial DNA. Molecular evidence of R. bellii was found in 25/108 (23.1%) and of Rickettsia sp. strain Cooperi (R. parkeri-like agent) in 2/108 (1.9%) of the A. dubitatum samples. These results suggest a greater exposure to R. bellii in these capybara populations, in addition to a more significant number of A. dubitatum, which might characterize the Federal District region as not endemic for Brazilian spotted fever.

Highlights

The number of herds of capybaras (Hydrochoerus hydrochaeris) has increased in several recreational areas in the Federal District, Brazil, and cases of tick infestations on people who visit these places are commonly reported in the media (G1, 2017; Medeiros, 2018)
Twenty-one samples (39.6%), including capybaras from all sampled areas, identified the R. bellii antigen as a probable antigen involved in a homologous reaction (PAIHR), with titration at least four times higher than the antigens of the other tested species
The Federal District is considered a non-endemic area for Brazilian Spotted Fever (BSF) (Brasil, 2019a, b)

Summary

Introduction

The number of herds of capybaras (Hydrochoerus hydrochaeris) has increased in several recreational areas in the Federal District, Brazil, and cases of tick infestations on people who visit these places are commonly reported in the media (G1, 2017; Medeiros, 2018). Maintenance of tick populations can be directly associated with capybaras, which are considered primary hosts for these arthropods (Horta et al, 2004; Luz et al, 2019). Pathogens of the genus Rickettsia (Rickettsiales: Rickettsiaceae) are Gram-negative obligate intracellular bacteria transmitted by arthropod vectors (Darby et al, 2007). Within this genus, the spotted fever group (SFG) includes zoonotic agents such as Rickettsia rickettsii and Rickettsia parkeri, which can cause acute febrile human illness, as is the case of the Brazilian Spotted Fever (BSF) and the Rocky Mountain Spotted Fever, caused by R. rickettsii (Pacheco et al, 2007). Sanitary monitoring of populations of capybaras is essential for the control and maintenance of public health

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Results

Conclusion