Epidemiology of capybara-associated Brazilian spotted fever

Abstract

BackgroundBrazilian spotted fever (BSF), caused by the bacterium Rickettsia rickettsii, has been associated with the transmission by the tick Amblyomma sculptum, and one of its main hosts, the capybara (Hydrochoerus hydrochaeris).MethodsDuring 2015–2019, we captured capybaras and ticks in seven highly anthropic areas of São Paulo state (three endemic and four nonendemic for BSF) and in two natural areas of the Pantanal biome, all with established populations of capybaras.ResultsThe BSF-endemic areas were characterized by much higher tick burdens on both capybaras and in the environment, when compared to the BSF-nonendemic areas. Only two tick species (A. sculptum and Amblyomma dubitatum) were found in the anthropic areas; however, with a great predominance of A. sculptum (≈90% of all ticks) in the endemic areas, in contrast to a slight predominance of A. dubitatum (≈60%) in the nonendemic areas. Tick species richness was higher in the natural areas, where six species were found, albeit with a predominance of A. sculptum (≈95% of all ticks) and environmental tick burdens much lower than in the anthropic areas. The BSF-endemic areas were characterized by overgrowth populations of A. sculptum that were sustained chiefly by capybaras, and decreased populations of A. dubitatum. In contrast, the BSF-nonendemic areas with landscape similar to the endemic areas differed by having lower tick burdens and a slight predominance of A. dubitatum over A.sculptum, both sustained chiefly by capybaras. While multiple medium- to large-sized mammals have been incriminated as important hosts for A. sculptum in the natural areas, the capybara was the only important host for this tick in the anthropic areas.ConclusionsThe uneven distribution of R. rickettsii infection among A. sculptum populations in highly anthropic areas of São Paulo state could be related to the tick population size and its proportion to sympatric A. dubitatum populations.

Human-induced changes in habitat preference by capybaras (Hydrochoerus hydrochaeris) and their potential effect on zoonotic disease transmission

“…Forests are preferred ecological niche of A. sculptum ticks [19, 56, 57], the main vectors of the BSF agent ( R. rickettsii ) [16]. In particular, environmental tick burdens were found to be much higher across human-modified landscapes than across natural landscapes studied here [19].…”

“…Forests are preferred ecological niche of A. sculptum ticks [19, 56, 57], the main vectors of the BSF agent ( R. rickettsii ) [16]. In particular, environmental tick burdens were found to be much higher across human-modified landscapes than across natural landscapes studied here [19]. Therefore, capybaras may be highly efficient hosts across human-modified landscapes, increasing their capacity in maintaining and carrying large numbers of A. sculptum [16, 19], due to shared preferences for forested habitats.…”

“…It is important to emphasize that no case of BSF has been reported in Mato Grosso and Mato Grosso do Sul states, and serological analyses of capybaras from these natural landscapes have shown no evidence of R. rickettsii exposure [19]. In contrast, at least three study areas of human-modified landscapes in São Paulo state were classified as BSF-endemic (municipalities of Americana, Araras and Piracicaba), with recent occurrence of human cases and serological evidence of R. rickettsii infection in capybaras [19].…”

“…Capybaras can also act as amplifying hosts of R. rickettsii among A. sculptum populations [16, 17]. Even though the role of capybaras in BSF epidemiology have been well-discussed [16, 17, 18, 19], little is known about the potential effects of human-driven variation in capybara habitat selection to BSF spread and transmission.…”

Ticks and Associated Pathogens From Rescued Wild Animals in Rainforest Fragments of Northeastern Brazil

“…only in DNA samples extracted from ticks collected from mammalian hosts. Rickettsia rickettsii and Rickettsia parkeri are causative species of tick-borne spotted fever in Brazil, and these pathogens were found in this country in ticks collected from capybaras in Mato Grosso state (71) and from dogs in Bahia state (72). Rickettsia bacteria have been reported in ticks infesting several wild mammalian species throughout Brazil (73)(74)(75)(76), and in Brazilian wild birds (77,78).…”