Rickettsia parkeri in the Pampa biome of southern Brazil: Isolation, molecular characterization, and serological evidence of canine infection

In this work we performed a field study in a spotted fever-endemic area of the Pampa biome in Rio Grande do Sul, the southernmost state of Brazil (Rosário do Sul municipality), with the aim to evaluate the serological status of dogs for spotted fever group (SFG) rickettsiae, to attempt the isolation rickettsiae from A. tigrinum ticks, and to further perform a multi-genic molecular characterization of the rickettsial isolate. For this purpose, we collected blood serum samples and ticks from 18 rural dogs during 2016-2017. By immunofluorescence assay, all 18 dogs (100%) reacted serologically to SFG rickettsiae, with highest endpoint titers to R. parkeri, suggesting that at least part of these dogs have been infected by R. parkeri. Among 23 ticks collected from the dogs (13 A. tigrinum and 10 Rhipicephalus sanguineus sensu stricto), 46% (6/13) A. tigrinum contained DNA of R. parkeri, which was successfully isolated in Vero cell culture from one of these ticks. Partial sequences of five genes (gltA, ompA, virB4, dnaA, dnaK) and 3 intergenic spacers (mppA-purC, rrl-rrf-ITS, rpmE-tRNA^fMet) were generated from this rickettsial isolate, and were all 100% identical to corresponding sequences of R. parkeri s.s. We provide the first report of a viable isolate of R. parkeri from A. tigrinum, confirming that this isolate belongs to the strain R. parkeri s.s., as it has already been demonstrated for other two tick species of the Amblyomma maculatum species complex (A. maculatum and Amblyomma triste).

A putative novel strain of Ehrlichia infecting Amblyomma tigrinum associated with Pampas fox (Lycalopex gymnocercus) in Esteros del Iberá ecoregion, Argentina

The current work evaluated road-killed Pampas foxes (Lycalopex gymnocercus) and their ticks for the presence of vector-borne agents in the ecoregion Esteros del Iberá in northeastern Argentina. Spleen, lung and blood samples and Amblyomma tigrinum adult ticks collected from the foxes were tested by polymerase chain reaction (PCR) assays targeting bacteria of the genera Ehrlichia, Anaplasma, and Rickettsia. All foxes tested were negative for the three genera, but evidence of Ehrlichia and Rickettsia infection was detected in the ticks. One A. tigrinum (out of 12 tested) was infected by an ehrlichial agent, here named Ehrlichia sp. strain Iberá, related to ehrlichial agents recently detected in platypuses in Tasmania (Ornithorhynchus anatinus) and in voles (Myodes rutilus and Myodes rufocanus) and shrews (Sorex araneus) in the Russian Far East. Regarding Rickettsia, all A. tigrinum ticks (100%) were infected by ´Candidatus Rickettsia andeanae´, a member of the spotted fever group rickettsia of unknown pathogenicity. Further research is necessary to unveil the ecology of Ehrlichia sp. strain Iberá as well as its zoonotic relevance. The species of the genus Ehrlichia are known to be pathogenic to mammals, including humans and domestic animals, thus the presence of this ehrlichial agent in A. tigrinum is a potential risk for veterinary and public health, as the adults of A. tigrinum are common parasites of dogs in rural and peri-urban environments, and humans are also frequently bitten by this tick species.

[Amblyomma triste and Amblyomma tigrinum (Acari: Ixodidae) in sympatry in Santa Fe Province, Argentina]

The aim of this communication is to report, for the first time, the occurrence of Amblyomma triste in Santa Fe province, Argentina, and to add a new isolation place for Amblyomma tigrinum. Both species of ticks are vectors of Rickettsia parkeri, a spotted fever group rickettsia. Ticks were recovered from tourists in August 2014 and December 2015 at the Federico Wildermuth Foundation (31° 59'S, 61° 24'O), San Martin Department, Santa Fe province. Five adult ticks were morphologically identified as A. tigrinum (3 females and 1 male) and A. triste (1 female). This is the first finding including both Amblyomma maculatum group species, A. triste and A. tigrinum, together in the same locality in Argentina. This finding suggests that this site might have favorable features for the development of both species of R. parkeri vector. Further studies including sampling of a larger number of ticks and detection of R. parkeri DNA are needed to better document the epidemiology of this rickettsia in Santa Fe.

First molecular detection of Rickettsia parkeri in Amblyomma tigrinum and Amblyomma dubitatum ticks from Uruguay

Rickettsia parkei is the etiological agent of spotted fever in Uruguay, where is transmitted to humans by the tick Amblyomma triste. In the present study, ticks were collected from capybaras (Hydrochoerus hydrochaeris) and domestic dogs during 2011-2012 in different parts of Uruguay. Three out of 11 (27.3%) Amblyomma dubitatum ticks collected from capybaras, and 4 out of 6 (66.7%) Amblyomma tigrinum ticks collected from dogs were shown by molecular analyses to be infected by Rickettsia parkeri strain Maculatum 20. Until the present work, A. triste was the only tick species that was found infected by R. parkeri in Uruguay. This is the first report of R. parkeri infecting these two tick species in Uruguay, expanding the current distribution of this rickettsial pathogen in the country.