Phylogenetic Evidence for the Existence of Multiple Strains of Rickettsia parkeri in the New World

Free PMC Article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5881050/The bacterium Rickettsia parkeri has been reported to infect ticks of the "Amblyomma maculatum species complex" in the New World, where it causes spotted fever illness in humans. In South America, three additional rickettsial strains, namely, Atlantic rainforest, NOD, and Parvitarsum, have been isolated from the ticks Amblyomma ovale, Amblyomma nodosum, and Amblyomma parvitarsum, respectively. These three strains are phylogenetically closely related to R. parkeri, Rickettsia africae, and Rickettsia sibirica Herein, we performed a robust phylogenetic analysis encompassing 5 genes (gltA, ompA, virB4, dnaA, and dnaK) and 3 intergenic spacers (mppE-pur, rrl-rrf-ITS, and rpmE-tRNAfMet) from 41 rickettsial isolates, including different isolates of R. parkeri, R. africae, R. sibirica, Rickettsia conorii, and strains Atlantic rainforest, NOD, and Parvitarsum. In our phylogenetic analyses, all New World isolates grouped in a major clade distinct from the Old World Rickettsia species (R. conorii, R. sibirica, and R. africae). This New World clade was subdivided into the following 4 clades: the R. parkerisensu stricto clade, comprising the type strain Maculatum 20 and all other isolates of R. parkeri from North and South America, associated with ticks of the A. maculatum species complex; the strain NOD clade, comprising two South American isolates from A. nodosum ticks; the Parvitarsum clade, comprising two South American isolates from A. parvitarsum ticks; and the strain Atlantic rainforest clade, comprising six South American isolates from the A. ovale species complex (A. ovale or Amblyomma aureolatum). Under such evidences, we propose that strains Atlantic rainforest, NOD, and Parvitarsum are South American strains of R. parkeriIMPORTANCE Since the description of Rickettsia parkeri infecting ticks of the "Amblyomma maculatum species complex" and humans in the New World, three novel phylogenetic close-related rickettsial isolates were reported in South America. Herein, we provide genetic evidence that these novel isolates, namely, strains Atlantic rainforest, NOD, and Parvitarsum, are South American strains of R. parkeri. Interestingly, each of these R. parkeri strains seems to be primarily associated with a tick species group, namely, R. parkerisensu stricto with the "Amblyomma maculatum species group," R. parkeri strain NOD with Amblyomma nodosum, R. parkeri strain Parvitarsum with Amblyomma parvitarsum, and R. parkeri strain Atlantic rainforest with the "Amblyomma ovale species group." Such rickettsial strain-tick species specificity suggests a coevolution of each tick-strain association. Finally, because R. parkerisensu stricto and R. parkeri strain Atlantic rainforest are human pathogens, the potential of R. parkeri strains NOD and Parvitarsum to be human pathogens cannot be discarded.This work was supported by Fundação de Amparo à Pesquisa do Estado de São Paulo (grant 2011/51979-1 to F.A.N.-B.) and by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior CAPES/PROEX 1841/2016.info:eu-repo/semantics/publishedVersio

Anti rickettsia-antibody for spotted fever group in horses and dogs in the North of Paraná Stated, Brazil

The Brazilian Spotted Fever (BSF) is a zoonosis that can be fatal if not trteated. As there are few studies of the BSF in the Paraná State, the occurrence of BSF was serologically investigated in dogs and horses by indirect immunofluorescence assay (IFA), in the North of that State, in animals that are regarded as sentinels for BSF. A total of 241 samples of sera of equine, four of asinine, and 29 of dogs were collected in nine farms of three municipalities in the North of Paraná: Arapongas, Douradina, and Umuarama. From fifteen samples of equine serum with positive titres for RIFI, eight (53.3 %) had titre of 64 against R. rickettsii, two (13.3 %) 128 against R. rickettsii, and five (33.3 %) were reactants for R. parkeri and R. rickettsii, with titres ranging from 64 to 2048, and 128 to 1024, respectively. The results showed that domestic animals, sentinels for BSF, are under low exposition to ticks infected with spotted fever group Rickettsia, indicating low risk of human infection by these agents in the studied area

Amblyomma parvum Aragao, 1908 (Acari: Ixodidae) : phylogeography and systematic considerations

The geographical distribution of Amblyomma parvum Arag\ue3o 1908 in the New World is disjunct, with two main clusters separated from each other by the Amazon basin. The main objectives of this study were to further investigate the systematic relationships within A. parvum, to determine whether or not populations from different geographical areas might represent cryptic species, and to reconstruct the phylogeographical evolutionary history of the species. The genetic diversity of A. parvum collected throughout its distributional range was analyzed by using 6 molecular markers: 5 mitochondrial [the small and the large ribosomal subunits 12rDNA and 16SrDNA, the cytochrome oxidase I (COI) and II (COII) and the control region or d-loop (DL)], and one nuclear (ITS2, Inter transcribed spacer 2). Phylogenetic trees were inferred by using maximum parsimony and Bayesian analyses. In addition, node dating was attempted for the main lineages identified phylogenetically. Although mitochondrial and nuclear topologies were not totally congruent, they all identified at least two main supported clusters, a Central American lineage, and a Brazilian-Argentinian lineage. Clade support and divergence values strongly suggest that the two lineages correspond to different taxonomic entities. Node dating placed the split between the Central American and the Brazilian-Argentinian lineages at approximately 5.8-4.9 Mya, just after the progressive replacement of the dry areas that occupied the northern part of South America by the Amazon Basin in the early-mid Miocene. This event might be the cause of fragmentation and putative speciation within the ancestral relatively xerophilic A. parvum population

Molecular detection of Rickettsia rickettsii, Ehrlichia canis and Rangelia vitalli in Rhipicephalus sanguineus senso latu collected from dogs in Brazil

ABSTRACT This study evaluated by molecular methods the presence of major canine tick-borne agents in ticks infesting domestic dogs of a hospital population in a neglected area of the southern zone of the São Paulo Metropolitan region, which is characterized by an extensive urban area surrounded and interspersed by forest remnants of the original Atlantic rainforest. During 2017, 106 tick specimens - 71 adults and 33 nymphs of Rhipicephalus sanguineus sensu lato (s.l.), and two adults of Amblyomma aureolatum - were collected from 41 dogs that were attended in a Veterinary Teaching Hospital in São Paulo City, Brazil. By molecular analyses, 4.2% (3/71) of the R. sanguineus s.l. adult ticks contained the bacterium Rickettsia rickettsii, 2.8% (2/71) contained the bacterium Ehrlichia canis, and 4.2% (3/71) contained the protozoan Rangelia vitalii. These results indicate that domestic dogs of the southern zone of the São Paulo metropolitan region might be exposed to three of the major tick-borne agents affecting dogs in Brazil, R. rickettsii, E. canis and R. vitalii. In addition, the findings reinforce the circulation of the human pathogen R. rickettsii in the study area in a likely enzootic cycle involving dogs and R. sanguineus ticks