Molecular detection of rickettsial bacteria in ticks of the genus Ixodes from the Southern Cone of America

Population genetics of the Ixodes affinis (Ixodida: Ixodidae) complex in America: new findings and a host-parasite review

Ticks are hematophagous ectoparasites associated with a wide range of vertebrate hosts. Within this group, the Ixodidae family stands out, in which the Ixodes genus contains at least 245 species worldwide, from which 55 species are present in the Neotropical region. Ixodes affinis, a tick described in 1899, has a wide distribution from the Southern Cone of America to the United States. However, since its description, morphological variability has been reported among its populations. Furthermore, attempts have been made to clarify its status as a species complex using mitochondrial markers, but mainly in restricted populations of South and Central America. Thus, information related to populations of the transition region between the Neotropical and Nearctic zones is lacking. For these reasons, the objectives of the study were to evaluate the genetic diversity and structure of I. affinis across the Americas and to compile all the published records of I. affinis in America, to elucidate the host-parasite relationships and to identify their geographical distribution. For this, a phylogeny, and AMOVA analyses were performed to assess the genetic structure of samples obtained by field work in South Carolina, USA and Yucatán, Mexico. A total of 86 sequences were retrieved from a fragment of the 16S region. Phylogeny and genetic structure analysis showed four groups that were geographically and genetically related with high branch support and Fst values, all of them statistically significant. The results obtained support the hypothesis that I. affinis it corresponds to a complex of four species, which must be validated through future morphological comparisons.

Ticks (Acari: Ixodidae, Argasidae) associated with wild birds in Argentina

The aim of this study was to report tick infestations on wild birds from four Phytogeographic Provinces of Argentina. A total of 1085 birds was captured (124 species, 97 genera, 29 families and 13 orders), and ticks were collected from 265 birds (48 species, 40 genera and five orders). A total of 1469 ticks (1102 larvae, 363 nymphs and 4 females) belonging to 15 tick species (Amblyomma calcaratum, Amblyomma dubitatum, Amblyomma nodosum, Amblyomma ovale, Amblyomma parvum, Amblyomma sculptum, Amblyomma tigrinum, Amblyomma triste, Haemaphysalis juxtakochi, Haemaphysalis leporispalustris, Ixodes auritulus sensu lato, Ixodes pararicinus, Ixodes silvanus, Ixodes sp. cf. I. affinis and Ornithodoros sp. cf. O. mimon). Eighty-one new associations between bird species and stages of tick species are detected. The families Thamnophilidae, Turdidae, Thraupidae, Passerellidae, Furnariidae and Troglodytidae were the most prevalent. According to the Phytogeographic Provinces involved in this study, the prevalence of infection for each of them in birds was: (1) Chaco: 28.2% (11 tick species); (2) Yungas: 22.0% (8 tick species); (3) Espinal: 11.1% (2 tick species); and (4) Pampa: 3.9% (1 tick species). This study provided information on the diversity of tick species that parasitize wild birds, the variability of the specific tick-bird associations between the different Phytogeographic Provinces and the relevance of some families of birds as hosts of different tick species.

Multilocus genetic analysis indicates taxonomic status of "Candidatus Rickettsia mendelii" as a separate basal group

To date, the phylogeny of Rickettsia spp. from basal groups is based on the small number of identified species. Thus, the finding of "Candidatus Rickettsia mendelii" in 2016 is of great interest. In this study, "Ca. R. mendelii" was first identified in the Asian region in a new carrier, Ixodes pavlovskyi. "Candidatus R. mendelii", along with "Candidatus Rickettsia tarasevichiae", were found in Ixodes ticks collected on Russky Island (the Far East), where I. pavlovskyi coexists with I. persulcatus. To establish the taxonomic position of "Ca. R. mendelii", a detailed genetic study was carried out. "Candidatus R. mendelii" was genotyped by five genetic fragments (16S rRNA, gltA, and ompB genes, groESL operon, and 23S-5S IGS region); among them, the ompB gene, groESL operon and 23S-5S IGS region were sequenced for the first time. In addition, "Ca. R. tarasevichiae" was genetically characterized by eight genetic loci (16S rRNA, gltA, ompA, ompB, sca4, htrA genes, groESL operon, and 23S-5S IGS region), of which the sca4 gene was first determined. Phylogenetic analysis indicated that regardless of analyzed genetic loci, "Ca. R. mendelii" formed a separate well-supported cluster on each phylogenetic tree. Phylogenetic analysis based on concatenated sequences of gltA, ompB, and groEL gene fragments (total length of 3191 bp) demonstrated that "Ca. R. mendelii", like Rickettsia bellii, is a basal group of Rickettsia.

Rickettsia spp., Ehrlichia sp. and Candidatus Midichloria sp. associated to ticks from a protected urban area in Buenos Aires City (Argentina)

The aim of this study was to determine the infection with Rickettsiales in ticks and birds from the main protected urban area of Buenos Aires City (Argentina). One Amblyomma aureolatum (0.2%) and one Ixodes auritulus (0.1%) were positive by PCR targeting Rickettsia 23S-5S rRNA intergenic spacer. Phylogenetic analysis shows to findings in A. aureolatum are closely to Rickettsia bellii and for I. auritulus are related to 'Candidatus Rickettsia mendelii'. One I. auritulus (0.1%) and three A. aureolatum (0.6%) were positive by PCR for a fragment of the 16S rRNA gene of the Anaplasmataceae family. The sequences obtained from A. aureolatum were phylogenetically related to Midichloriaceae endosymbionts. The sequence from I. auritulus s.l. had 100% identity with Ehrlichia sp. Magellanica from Chile and two genotypes of Ehrlichia sp. from Uruguay. The results of our study show that Rickettsia and Ehrlichia are present in ticks in the main protected urban area of Buenos Aires City.

Molecular detection of Rickettsia sp. cf. Rickettsia monacensis in Ixodes sp. cf. Ixodes affinis collected from white-tailed deer in Campeche, Mexico

Deer encompass a group of large-sized vertebrates that serve as hosts for a wide variety of ectoparasites, mainly ticks. In Mexico, ticks have relevance as vectors of pathogenic microorganisms, and 20 species of hard ticks are associated with four species of deer, although only a single study has been conducted to detect bacterial agents associated with ticks from deer in the country. In February, 2019 three white-tailed deers (Odocoileus virginianus) were hunted from the locality of Chiná from the municipality of Campeche, Mexico. The sampled deers were parasitized by 26 ticks belonged to three species: Amblyomma mixtum (5♀, 1♂), Amblyomma ovale (2♀, 1♂), and Ixodes sp. cf. Ixodes affinis (15♀, 2♂). Specimens were screened individually for Anaplasma, Borrelia, Ehrlichia, and Rickettsia DNA by the amplification of several fragments of 16S rRNA, gltA, 17-kDa, and flaB genes. This study report for the first time the presence of Rickettsia sp. cf. Rickettsia monacensis in Ixodes sp. cf. Ixodes affinis in Mexico.

Molecular screening for tick-borne bacteria and hematozoa in Ixodes cf. boliviensis and Ixodes tapirus (Ixodida: Ixodidae) from western highlands of Panama

The first molecular screening for Rickettsia, Anaplasma, Ehrlichia, Borrelia, Babesia and Hepatozoon was carried out in questing Ixodes cf. boliviensis and Ixodes tapirus from Talamanca Mountains, Panama, using specific primers, sequencing and phylogeny. Phylogenetic analyses for the microorganisms in Ixodes cf. boliviensis confirmed the presence of Rickettsia sp. strain IbR/CRC endosymbiont (26/27 ticks), three genotypes of the Borrelia burgdorferi (sensu lato) complex (4/27 ticks), Babesia odocoilei (1/27 ticks), and Hepatozoon sp. (2/27 ticks), tentatively designated Hepatozoon sp. strain Chiriquensis. Phylogenetic analyses for the microorganisms in I. tapirus revealed an undescribed Rickettsia sp., tentatively designated Rickettsia sp. strain Itapirus LQ (6/6 ticks), and Anaplasma phagocytophilum (2/6 ticks). To the best of our knowledge, this is the first report of B. burgdorferi (s.l.) complex, A. phagocytophilum, B. odocoilei, and Hepatozoon sp. in Ixodes ticks from Central America, and also the first detection of Rickettsia spp. in Ixodes species in Panama. In light of the importance of these findings, further studies are needed focusing on the role of I. tapirus and I. cf. boliviensis as vectors, and the vertebrates acting as reservoirs.

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Free-living adult Ixodes ticks collected in Talamanca Mountains, Panama, were PCR-screened for tick-borne pathogens.

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Ixodes tapirus and Ixodes cf. boliviensis identified morphologically and molecularly.

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Genetic differences between Ixodes boliviensis from South America and I. cf. boliviensis from Panama.

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First molecular data for B. burgdorferi (s.l.), Hepatozoon and Babesia odocoilei in I. cf. boliviensis from Central America.

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First molecular data for Anaplasma phagocytophilum and spotted fever group Rickettsia in I. tapirus from Central America.

Rickettsia spp. in ticks (Acari: Ixodidae) from wild birds in Caldas, Colombia

Several bacteria belonging to the genus Rickettsia are recognized as causal agents of diseases in domestic and wild animals and humans. These bacteria are considered emerging or reemerging and are transmitted by ticks, fleas, and lice vectors. In recent decades, there have been reports of rickettsias in ticks of the genus Amblyomma, Ixodes, and Haemaphysalis collected from wild birds. Accordingly, birds play a plausible role in the transport and spread of ticks infected by Rickettsia spp. In this study, we performed molecular detection of Rickettsia species in ticks collected from wild birds in the department of Caldas, Colombia. We detected and identified Rickettsia amblyommatis, 'Candidatus Rickettsia colombianensi' and a Rickettsia sp. closely related to 'Candidatus Rickettsia tarasevichiae' and Rickettsia canadensis. This study contributes to the knowledge on infection by Rickettsia in ticks collected from wild birds in Colombia. We also provide the first reports of infection by R. amblyommatis in the genus Ixodes collected from wild birds in South America and the presence of Rickettsia at elevations above 3000 m a.s.l.