Rickettsia species infecting Amblyomma ticks from an area endemic for Brazilian spotted fever in Brazil

Abstract

This study reports rickettsial infection in Amblyomma cajennense and Amblyomma dubitatum ticks collected in an area of the state of Minas Gerais, Brazil, where Brazilian spotted fever is considered endemic. For this purpose, 400 adults of A. cajenennse and 200 adults of A. dubitatum, plus 2,000 larvae and 2,000 nymphs of Amblyomma spp. were collected from horses and from the vegetation. The ticks were tested for rickettsial infection through polymerase chain reaction (PCR) protocols targeting portions of three rickettsial genes (gltA, ompA, and ompB). Only two free-living A. cajennense adult ticks, and four pools of free-living Amblyomma spp. nymphs were shown to contain rickettsial DNA. PCR products from the two A. cajennense adult ticks were shown to be identical to corresponding sequences of the Rickettsia rickettsii strain Sheila Smith. DNA sequences of gltA-PCR products of the four nymph pools of Amblyomma spp. revealed a new genotype, which was shown to be closest (99.4%) to the corresponding sequence of Rickettsia tamurae. Our findings of two R. rickettsii-infected A. cajennense ticks corroborate the endemic status of the study area, where human cases of BSF were reported recently. In addition, we report for the first time a new Rickettsia genotype in Brazil.

Transmission dynamics and control of Rickettsia rickettsii in populations of Hydrochoerus hydrochaeris and Amblyomma sculptum

“…In this scenario, the average fraction of infected detached larvae is 1.25% (95% CI = 0%-7.04%), infected attached larvae 0.7% (95% CI = 0%-6.5%), infected detached nymphs 1.35% (95% CI = 0%-9.36%), infected attached nymphs 0.8% (95% CI = 0%-6.95%), infected detached adults 0.46% (95% CI = 0%-5.17%) and infected attached adults 0.54% (95% CI = 0%-5.64%). These results are consistent with previous observations in BSF-endemic areas in which the fraction of infected A. sculptum adults attached to horses has been reported at 0% [28] and the fraction of infected detached adults A. sculptum at 1% (95% CI = 0.01%-7.8%) [28], 0.2% (95% CI = 0.01%-1.04%) [10] and 1.28% (95% CI = 0.07%-5.59%) [29]. The fraction of infected capybaras and other tick populations remains unreported.…”

Rickettsia rickettsiiCo-feeding Transmission amongAmblyomma aureolatumTicks

“…When nymphs derived from engorged larvae that had fed with R. rickettsii IN within the same chamber (UL + IN), absence of rickettsial transmission was demonstrated in 4 guinea pigs (nos. 24, 25, 28, 29), whereas rickettsial transmission was demonstrated by fever and seroconversion in 2 guinea pigs (nos. 26, 27).…”

Update on Tick-Borne Rickettsioses around the World: a Geographic Approach

“…The Pampulha strain, recently reported in A. dubitatum ticks in Brazil (201)(202)(203), and the Colombianensi strain, reported in Amblyomma dissimile and Rhipicephalus (Boophilus) microplus ticks in Colombia (204), are two distinct strains that are closely related to the Old World species Rickettsia tamurae and Rickettsia monacensis. In Brazil, only a few populations of A. dubitatum have been found to be infected by the Pampulha strain; however, infection rates are usually very high among the infected populations (203).…”