A novel Ehrlichia strain (Rickettsiales: Anaplasmataceae) detected in Amblyomma triste (Acari: Ixodidae), a tick species of public health importance in the Southern Cone of America

Wild birds as hosts of ticks (Acari: Ixodidae) and Anaplasmataceae (Rickettsiales) in the Atlantic rainforest ecoregion, Argentina

This study aimed to assess the presence of Anaplasma, Ehrlichia and Rickettsia species infecting wild birds and their associated ticks in two localities: Moconá Provincial Park (MPP) and Piñalito Provincial Park (PPP), within the Atlantic rainforest ecoregion of Argentina. A total of 142 birds were captured representing 34 species, 28 genera, 15 families and five orders. Ticks were collected from 33 of these birds, comprising 19 species, 14 genera and one order. A total of 59 ticks were collected and identified as Amblyomma calcaratum (13 larvae and four nymphs), Amblyomma longirostre (31 larvae and four nymphs), Amblyomma ovale (one larva and one nymph) and Haemaphysalis leporispalustris (five larvae). All samples were screened for detection of Anaplasma, Ehrlichia and Rickettsia DNA by polymerase chain reaction (PCR) assay. Four bird species tested positive for Anaplasmataceae, with three closely related to Anaplasma and Ehrlichia species previously reported in A. calcaratum adults from a site 15 km away from MPP. The fourth Anaplasmataceae agent was phylogenetically related to Ehrlichia strains reported in Amblyomma triste from the Delta and Parana Islands ecoregion. Additionally, two Rickettsia species were detected and molecularly identified within ticks collected from birds: Rickettsia amblyommatis in A. longirostre larvae and Rickettsia rhipicephali in H. leporispalustris larvae. These findings suggest that birds may play a significant role in the spread of ticks and their associated tick-borne pathogens across diverse biomes.

Molecular detection of Candidatus Ehrlichia pampeana (Rickettsiales: Anaplasmataceae) in Haemaphysalis juxtakochi (Acari: Ixodidae) from central Argentina

The aim of this study was to report the first detection of Candidatus Ehrlichia pampeana in Haemaphysalis juxtakochi from Argentina. Free-living ticks were collected from vegetation by drag-flag method on five sample sites in Entre Ríos Province, central Argentina, belonging to the Espinal Phytogeographic Province. Molecular detection of order Rickettsiales agents was performed using gltA (Rickettsia spp.), 16 S rRNA and groEL (Anaplasmataceae) genes as targets. A total of 67 ticks of Amblyomma aureolatum (20 nymphs and 4 adults), Amblyomma dubitatum (15 nymphs) and Haemaphysalis juxtakochi (24 nymphs and 4 adults) were collected. While all tested ticks were negative for Rickettsia spp., and Anaplasmataceae agents could neither be detected in A. aureolatum nor in A. dubitatum, Candidatus Ehrlichia pampeana was detected in one male of H. juxtakochi. DNA sequences of this microorganism (16 S rDNA and groEL) are related to sequences of Ehrlichia ewingii. The findings of the current study represent the first report of this Ehrlichia strain for Argentina.

Tick-borne microorganisms in Amblyomma tigrinum (Acari: Ixodidae) from the Patagonian region of Argentina

This study presents the results of the molecular detection of tick-borne microorganisms in Amblyomma tigrinum Koch collected near the city of Viedma, Río Negro, Argentina. Ticks were collected in their non-parasitic stage, on pet dogs and on Lycalopex gymnocercus (Pampa fox). Also, six tick samples from humans were analyzed. All ticks were morphologically identified to species level and genomic DNA was extracted. The DNA samples were examined by end point PCR assays to amplified DNA of Anaplasma sp., Babesia sp., Ehrlichia sp., Rickettsia sp. and Theileria sp. Although all tested DNA samples from the collected ticks resulted negative to the detection of Piroplasmida and Rickettsia spp., 16 samples (16.5%, including all hosts) were positive in the 16S rDNA gene PCR that detects bacteria from the Anaplasmataceae family. Phylogenetic analysis of seven obtained partial sequences resulted in the identification of three bacteria: two Ehrlichia spp. (related to Ehrlichia sp. strain Iberá and strain Viedma) and Candidatus Anaplasma boleense. The latter finding represents the first detection of this novel Candidatus species in A. tigrinum. Based on the results of this study, it must be assumed that the diversity of bacteria of the Anaplasmataceae family in Argentina is greater than previously thought, and that these bacteria can infect a wide range of domestic and wild animals.

Anaplasmataceae presence in Amblyomma calcaratum associated with anteaters (Tamandua tetradactyla) in the rainforest ecoregion, Argentina

Bacteria of the sister genera Ehrlichia and Anaplasma (Anaplasmataceae) are obligate intracellular Alphaproteobacteria that are transmitted mostly through arthropod vectors. These agents can infect different vertebrate cells, depending on the species involved, and can cause diseases in animals and humans. In this study, we evaluated the presence of Anaplasmataceae bacteria in Amblyomma calcaratum ticks collected from a road-killed Tamandua tetradactyla in the Rainforest ecoregion in Argentina. All samples were screened for Anaplasmataceae DNA using a real-time PCR assay targeting the 16S rRNA gene. Evidence of Anaplasmataceae DNA was detected in three out of thirty-nine Am. calcaratum ticks. Phylogenetic analysis of a portion of 16S rRNA gene positioned one sample (Ehrlichia sp. strain Ac124) with Ehrlichia sequences and the other two samples with Anaplasma sequences; Anaplasma sp. strain Ac145 close to Anaplasma odocoilei and Anaplasma sp. strain Ac152 in an ancestral position to most Anaplasma species. The groEL sequence obtained showed that Ehrlichia sp. strain Ac124 was phylogenetically related to Ehrlichia sp. strain Iberá reported infecting Amblyomma tigrinum from Iberá wetlands in Argentina. Phylogenetic analysis using the rpoB sequence positioned Anaplasma sp. strain Ac145 close to the canine pathogen Anaplasma platys, while Anaplasma sp. strain Ac152 was positioned close to the bovine pathogen Anaplasma marginale. In this study, three Anaplasmataceae agents were detected in adults of Am. calcaratum associated with a T. tetradactyla. These results suggest that the number of Anaplasmataceae species, as well as their distribution, is largely unknown.

Molecular detection of Ehrlichia spp. in ticks parasitizing wild lagomorphs from Spain: characterization of a novel Ehrlichia species

Background

Several species belonging to the genus Ehrlichia are considered pathogenic for animals and humans. Although wildlife are known to play an important role in the epidemiology of these bacteria, information on the role of wild lagomorphs in their sylvatic cycle is limited. Thus, the objective of the present study was to assess the occurrence of Ehrlichia spp. in ticks collected from wild lagomorphs in Spanish Mediterranean ecosystems.

Methods

A total of 1122 pooled ticks (254 pools) collected from 506 wild rabbits (Oryctolagus cuniculus) and 29 Iberian hares (Lepus granatensis) were analysed using a nested PCR assay targeting the partial groEL gene. Ehrlichia spp.-positive samples were further subjected to a second PCR assay targeting 16S rRNA.

Results

Three (1.2%) tick pools comprising Rhipicephalus pusillus collected from nine wild rabbits were positive for Ehrlichia spp. All the Ehrlichia DNA sequences were identical, and use of sequence and phylogenetic analyses allowed us to identify a novel Ehrlichia species.

Conclusions

We provide evidence that a novel Ehrlichia species, named herein as ‘Candidatus Ehrlichia andalusi’, which may be of concern for animal and public health, is circulating in R. pusillus in Spanish Mediterranean ecosystems. Further studies are warranted to assess the epidemiology, pathogenicity and zoonotic potential of this Ehrlichia species.

Graphical Abstract

Molecular Detection of Candidatus Rickettsia andeanae and Ehrlichia sp. in Amblyomma pseudoconcolor Aragão, 1908 (Acari: Ixodidae) from the Argentinian Patagonia

This study presents the molecular detection of Candidatus Rickettsia andeanae and Ehrlichia sp. in Amblyomma pseudoconcolor Aragão, 1908 (Acari: Ixodidae) collected on a large hairy armadillo (Chaetophractus villosus (Desmarest, 1804)). On 12 October 2020, a specimen of C. villosus was found dead on the road in Río Negro province, Argentina. Molecular detection of Rickettsia and Ehrlichia agents was performed amplifying the gltA and 16S rRNA gene, respectively. One tick, determined morphologically and genetically as A. pseudoconcolor, was collected on C. villosus. The rickettsial agent detected in A. pseudoconcolor was identified as Candidatus Rickettsia andeanae. The Ehrlichia sp. strain showed high sequence similarity to different uncultured Ehrlichia sp. detected in horses, capybaras and Ixodes ornithorhynchi from Nicaragua, Brazil and Australia, respectively. The results of this study and previous findings suggest that A. pseudoconcolor may be a potential vector of some Rickettsia and Ehrlichia bacteria of unknown pathogenicity.

Two novel Ehrlichia (Rickettsiales: Anaplasmataceae) strains detected in ticks (Ixodida, Ixodidae) and opossums (Didelphimorphia: Didelphidae) in Argentina

The aim of this study is to determine if there is circulation of microorganisms of the genus Ehrlichia in opossums Didelphis albiventris and their ticks from the Humid Chaco in Argentina. Blood samples of 15 specimens of the opossum D. albiventris were analysed. Immature stages of the ticks Amblyomma ovale (Larvae=26; Nymphs=10), Amblyomma sculptum (Larvae=86; Nymphs=6) and Ornithodoros sp. cf. O. mimon (Larvae=90) were also analyzed. DNA was extracted individually from blood samples and ticks. Molecular detection of Ehrlichia agents was performed targeting two different loci: 16S rRNA and dsb gen. The phylogenetic analyses showed that the Ehrlichia sp. detected in D. albiventris in this study is identical to Ehrlichia sp. strain Natal previously detected in two marsupials from Brazil. Furthermore, a new Ehrlichia strain was amplified from an A. ovale nymph (named as Ehrlichia sp. strain El Bagual) which is phylogenetically closely related to a strain of Ehrlichia sp. detected in Bradypus tridactylus in Brazil. The findings of the current study represent the first report of these two strains of Ehrlichia for Argentina, showing that the diversity of Ehrlichia spp. is greater than previously assumed. Further studies should determine the epidemiological relevance of these findings.

Characterization of "Candidatus Ehrlichia Pampeana" in Haemaphysalis juxtakochi Ticks and Gray Brocket Deer (Mazama gouazoubira) from Uruguay

Human ehrlichiosis are scantily documented in Uruguay. The aim of this study was to investigate the presence of Ehrlichia spp. in Haemaphysalis juxtakochi and in a gray brocket deer (Mazama gouazoubira) from Uruguay. The presence of Ehrlichia DNA was investigated in free-living H. juxtakochi in five localities of southeast and northeast Uruguay, as well as blood, spleen, and ticks retrieved from a M. gouazoubira. Ehrlichia spp. DNA was detected in six out of 99 tick pools from vegetation, in the spleen of M. gouazoubira, and in one out of five pools of ticks feeding on this cervid. Bayesian inference analyses for three loci (16S rRNA, dsb, and groEL) revealed the presence of a new rickettsial organism, named herein as "Candidatus Ehrlichia pampeana". This new detected Ehrlichia is phylogenetically related to those found in ticks from Asia, as well as Ehrlichia ewingii from USA and Cameroon. Although the potential pathogenicity of "Ca. E. pampeana" for humans is currently unknown, some eco-epidemiological factors may be relevant to its possible pathogenic role, namely: (i) the phylogenetic closeness with the zoonotic agent E. ewingii, (ii) the evidence of H. juxtakochi parasitizing humans, and (iii) the importance of cervids as reservoirs for zoonotic Ehrlichia spp. The molecular detection of "Ca. E. pampeana" represents the third Ehrlichia genotype described in Uruguay.

Serological evidence of Ehrlichia minasensis infection in Brazilian dogs

Ehrlichia spp. are important tick-borne pathogens of animals in Brazil, and Ehrlichia canis is the most prevalent species infecting dogs. Moreover, Ehrlichia minasensis has also recently been identified as a novel ehrlichial agent that infects cattle in Brazil. The objective of this study was to determine whether dogs could be infected by E. minasensis. To investigate this possibility, sera (n = 429) collected from dogs in the Pantanal region were retrospectively analyzed for the presence of antibodies against E. canis and E. minasensis. Canine sera were screened by two isolates of E. canis in indirect immunofluorescence assay (IFA) and the majority (n = 298; 69.4%) had antibodies with endpoint titers ranging from 80 to 327,680. In order to further confirm E. canis-specific antibodies, IFA positive sera were analyzed by ELISA using E. canis-specific peptides (i.e. TRP19 and TRP36 US/BR/CR), which detected E. canis antibodies in 80.2% (239/298) of the dog sera. Fifty-nine (13.7%) samples had detectable antibodies to E. canis by IFA but were negative by E. canis peptide ELISA. These sera were then tested by E. minasensis IFA (Cuiaba strain) as antigen and 67.8% (40/59) were positive (titers ranging from 80 to 20,480). Eleven sera had antibody titers against E. minasensis at least two-fold higher than observed for E. canis and suggests that these dogs were previously infected with E. minasensis. The results of the present study suggest that multiple ehrlichial agents infect dogs in Brazil, which highlights the need to consider different Ehrlichia spp. in Brazilian dogs, particularly in areas where dogs are frequently exposed to multiple tick species. This investigation is the first to provide serologic evidence of E. minasensis infection in dogs from Brazil.

Detection of Ehrlichia sp. in Amblyomma sculptum parasitizing horses from Brazilian Pantanal wetland

Bacteria of the genus Ehrlichia are transmitted by ticks and also are an important cause of infection in wild and domestic mammals. Infection with Ehrlichia spp. has been reported in horses, especially in the USA, Nicaragua and Brazil. In this study, we report the parasitism by Amblyomma sculptum, Rhipicephalus microplus and Dermacentor nitens ticks in horses from a ranch located in south Pantanal wetland. Molecular and serological analyzes to determine infection by Ehrlichia spp. in horses and their respective ticks were carried out. A total of 12 horses were submitted to blood collection to investigate antibodies by indirect immunofluorescence assay (IFA) using Ehrlichia canis crude antigens and to be tested by polymerase chain reaction (PCR) in order to amplify fragments of the 16S rRNA, dsb, groEL and sodB gene of Ehrlichia spp. A total of 164 tick specimens were removed from horses, stored in isopropanol and later identified as D. nitens, A. sculptum and R. microplus. DNA from ticks were extracted and subjected to the same PCR assays to detect Ehrlichia spp. Anti-Ehrlichia spp. antibodies were detected in five/12 (41.7 %) horses by IFA, with antibody titers ranging from 40 to 160. All horse DNA samples were negative for the 16S rRNA, dsb, groEL and sodB of Ehrlichia spp. One A. sculptum female was positive to all target genes of Ehrlichia. This tick was parasitizing an Ehrlichia-seropositive horse with antibody titer of 80. Nucleotide sequences of 16S rRNA, dsb, groEL and sodB genes showed close relationship with different strains of Ehrlichia detected in wild mammals, Amblyomma ticks and horses from Brazil and Argentina. Detection of anti-Ehrlichia sp. antibodies suggests that horses have been exposed to an ehrlichial agent in the Pantanal. Future studies on Ehrlichia infection should be carried out to better elucidate and to bring new information about equine ehrlichiosis, since these animals are important hosts of ticks in the Brazilian Pantanal wetlands.

Epidemiological link between canine monocytic ehrlichiosis caused by Ehrlichia canis and the presence of Rhipicephalus sanguineus sensu stricto in Argentina

In this work, we analyze data that support an epidemiological link between cases of canine monocytic ehrlichiosis (CME) by Ehrlichia canis and the presence of Rhipicephalus sanguineus sensu stricto as vector in an endemic area for this tick in Argentina. In a blood sample of a 1-year-old toy poodle with CME compatible clinical signs, which showed CME typical morulae in monocytes in Giemsa-stained blood smear, DNA of E. canis was detected by PCR. Further, DNA of E. canis was also detected in a female of R. sanguineus s.s. collected on the infected dog. Rhipicephalus sanguineus s.s. is the only member of the R. sanguineus group that prevails in the study area. The results of this study suggest that R. sanguineus s.s. may play a more important role in the transmission of E. canis than it was assumed so far. The epidemiological link between CME cases and R. sanguineus s.s. as vector in temperate areas of Argentina described in this work contrast previous studies which found that R. sanguineus sensu lato "tropical lineage" (which is absent in the study area) is competent to transmit E. canis but not R. sanguineus s.s.

Molecular screening for rickettsial bacteria and piroplasms in ixodid ticks surveyed from white-tailed deer (Odocoileus virginianus) and nilgai antelope (Boselaphus tragocamelus) in southern Texas

A survey of ixodid ticks parasitizing white-tailed deer (Odocoileus virginianus) and nilgai antelope (Boselaphus tragocamelus) was completed during the 2018–2019 public hunt season on the Laguna Atascosa National Wildlife Refuge (Cameron County, Texas) and the East Foundation's El Sauz Ranch in nearby Willacy County (Texas). Anocenter nitens was the predominant tick species identified with 5% of these ticks collected from nilgai. All life stages were encountered in high numbers on white-tailed deer, indicating that deer may be a primary host in this region. Amblyomma maculatum and Amblyomma inornatum were identified from both hosts, while Ixodes scapularis was encountered only on white-tailed deer. This is the first published record of A. inornatum on nilgai. A subset of ticks was used in PCR assays to detect Rickettsia spp., family Anaplasmataceae, Borrelia spp., and Theileria-Babesia spp. Borrelia spp. were not detected in any of the ticks analyzed. Rickettsia parkeri was detected in three A. maculatum adult ticks from deer, Rickettsia sp. endosymbiont sequences were present in all I. scapularis ticks, and Rickettsia amblyommatis was detected in three A. inornatum adult ticks from deer. Sequence analysis of Anaplasmataceae-positive amplicons from A. nitens and A. maculatum had low percent identity to published Anaplasma spp. sequences, suggesting a unique Anaplasma sp. may be circulating in the population. Anaplasma platys was detected from A. nitens larvae and an Ehrlichia sp. Delta strain was present in A. maculatum, both of unknown pathogenicity towards deer. Theileria cervi was detected in all stages of A. nitens ticks, and positive ticks originated from 27 of 31 deer and a single nilgai sampled from throughout the survey site. The primary vector for T. cervi is absent from this region, suggesting T. cervi is possibly maintained by a different tick species.

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Anocenter nitens predominates on white-tailed deer and nilgai in southern Texas.

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Theileria cervi was detected in Anocenter nitens ticks from deer and a single nilgai.

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Three Theileria cervi genotypes were detected in this region of southern Texas.

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Unique Anaplasma sp. detected in A. nitens; low identity to known Anaplasma sp.

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Amblyomma inornatum ticks were identified on nilgai; a first record on this host.