The brown dog tick Rhipicephalus sanguineus sensu Roberts, 1965 across Australia: Morphological and molecular identification of R. sanguineus s.l. tropical lineage

The geographic limits and life history of the tropical brown dog tick, Rhipicephalus linnaei (Audouin, 1826), in Australia with notes on the spread of Ehrlichia canis

The tropical brown dog tick, Rhipicephalus linnaei, is a tick of much medical, veterinary, and zoonotic importance. This tick has a nearly world-wide distribution due to its ability to survive and propagate in kennels and houses. Rhipicephalus linnaei is the vector of Ehrlichia canis, the causative agent of canine monocytic ehrlichiosis, an often debilitating disease of canids and, occasionally, humans. To prevent incursion of E. canis into Australia, dogs entering Australia have been required to have a negative immunofluorescence antibody test for E. canis. In May 2020 however, E. canis was detected in Western Australia. The detection of E. canis in Australia prompted disease investigation and concerted surveillance for R. linnaei and E. canis in regions across Australia. These investigations revealed that R. linnaei was established far beyond the previously recognised geographic range limits of this tick. In the present paper, using records from various collections, published data, and data from our network of veterinarian collaborators and colleagues, we update the current geographic range of R. linnaei in Australia. Our analyses revealed that the geographic range of R. linnaei in Australia is much wider than was previously supposed, particularly in Western Australia, and in South Australia. We also map, for the first time, where E. canis has been detected in Australia. Last, we discuss the possible routes of incursion and subsequently the factors which may have aided the spread of E. canis in Australia which led to the establishment of this pathogen in Australia.

Initial study and phylogenetic analysis of hard ticks (Acari: Ixodidae) in Nantong, China along the route of avian migration

The growing concern about migratory birds potentially spreading ticks due to global warming has become a significant issue. The city of Nantong in this study is situated along the East Asia-Australasian Flyway (EAAF), with numerous wetlands serving as roosting sites for migratory birds. We conducted an investigation of hard ticks and determined the phylogenetic characteristics of tick species in this city. We utilized three different genes for our study: the mitochondrial cytochrome oxidase subunit 1 (COX1) gene, the second internal transcribed spacer (ITS2), and the mitochondrial small subunit rRNA (12 S rRNA) gene. The predominant tick species were Haemaphysalis flava (H. flava) and Haemaphysalis longicornis (H. longicornis). Additionally, specimens of Haemaphysalis campanulata (H. campanulata) and Rhipicephalus sanguineus (R. sanguineus) were collected. The H. flava specimens in this study showed a close genetic relationship with those from inland provinces of China, as well as South Korea and Japan. Furthermore, samples of H. longicornis exhibited a close genetic relationship with those from South Korea, Japan, Australia, and the USA, as well as specific provinces in China. Furthermore, R. sanguineus specimens captured in Nantong showed genetic similarities with specimens from Egypt, Nigeria, and Argentina.

Effect of an altitudinal gradient on the morphology, molecular identification and distribution of Rhipicephalus linnaei in Veracruz, Mexico

Studies of morphological and genetic variation in vector populations across environmental gradients can help researchers to estimate species' responses to climate change scenarios and the potential risk of disease-causing pathogen expansion, which impacts negatively on human health. In this study, we analysed the effect of altitudinal gradients on the phenotypic response of the hard tick of medical and veterinary importance, Rhipicephalus sanguineus sensu lato (s.l.). Specimens of R. sanguineus s.l. were collected from host animals in one of Mexico's regions with high climatic heterogeneity (Veracruz), and geometric morphometric theory was employed to assess the response of three morphological characters to the altitudinal gradient. Additionally, genetic similarity data were provided, and ecological niche models were used to project the climatic distribution in the region. Our results demonstrate that the shape and size of ticks respond to altitude. Molecular identification indicate that all analysed samples correspond to the tropical lineage recently named Rhipicephalus linnaei. According to ecological niche models, the mean annual temperature contributes significantly to the spatial distribution of this tick species, with areas of higher suitability in the mountainous region. These changes in morphological structure and the presence of ticks at higher altitudinal gradients suggest that R. linnaei has a high potential for adaptation. Due to the variability of ecosystems in the state of Veracruz, our results could be valuable in assessing the response of this tick in a changing environment, aiding in predicting future scenarios in the distribution and abundance of this species.

Canine Babesiosis Caused by Large Babesia Species: Global Prevalence and Risk Factors-A Review

Canine babesiosis is a disease caused by protozoan pathogens belonging to the genus Babesia. Four species of large Babesia cause canine babesiosis (B. canis, B. rossi, B. vogeli, and the informally named B. coco). Although canine babesiosis has a worldwide distribution, different species occur in specific regions: B. rossi in sub-Saharan Africa, B. canis in Europe and Asia, and B. coco in the Eastern Atlantic United States, while B. vogeli occurs in Africa, southern parts of Europe and Asia, northern Australia, southern regions of North America, and in South America. B. vogeli is the most prevalent large Babesia species globally. This results from its wide range of monotropic vector species, the mild or subclinical nature of infections, and likely the longest evolutionary association with dogs. The most important risk factors for infection by large Babesia spp. include living in rural areas, kennels or animal shelters, or regions endemic for the infection, the season of the year (which is associated with increased tick activity), infestation with ticks, and lack of treatment with acaricides.

Ehrlichia canis rapid spread and possible enzooty in northern South Australia and distribution of its vector Rhipicephalus linnaei

Recent concerns have arisen in Australia regarding detections of the exotic bacterium Ehrlichia canis which has resulted in ehrlichiosis outbreaks. In Australia, it is spread by the tropical brown dog tick Rhipicephalus linnaei, formerly Rhipicephalus sanguineus sensu lato tropical lineage. Previously, the tick has been recorded in South Australia in the Coober Pedy and the Oodnadatta areas. This study, which includes historical specimens data held in historical Australian arthropod collections, along with 10 sampled remote communities, confirms the wide distribution range of this species within the State. E. canis was detected by PCR in the ticks. The percentage of dogs hosting PCR-positive ticks increased from 2.8% (95% confidence interval [CI]: 0.3 to 9.7) in November-December 2020 to 62.9% (95% CI: 44.9 to 78.5) end of February 2021, initially in two then in seven Anangu Pitjantjatjara Yankunytjatjara lands communities in the far northern regions of South Australia. Our results suggest a rapid spread of the pathogen. No evidence of E. canis was found in nine regional communities. The extended tropical brown dog tick distribution indicates a greater area where E. canis may occur and may require management to minimise the impacts of ehrlichiosis outbreaks. Without the implementation of effective detection and control programs, this extended distribution of R. linnaei is likely to result in the spread of the bacterium to other regions.

Rhipicephalus linnaei (Audouin, 1826) recognised as the "tropical lineage" of the brown dog tick Rhipicephalus sanguineus sensu lato: Neotype designation, redescription, and establishment of morphological and molecular reference

We re-describe the adult stages of Rhipicephalus linnaei (Audouin, 1826), and characterise its diagnostic molecular traits. A male R. linnaei collected in Esna City, Luxor Governorate, Egypt is designated as the neotype. Rhipicephalus linnaei is re-established as a valid tick name and removed from the synonymy list of Rhipicephalus sanguineus (Latreille, 1806). Rhipicephalus linnaei is most similar to R. sanguineus and Rhipicephalus camicasi Morel, Mouchet & Rodhain, 1976 because they share similar elongated comma-like spiracula that are narrowly visible dorsally, and the dorsal prolongation is narrower than the width of the adjacent festoon. The male of R. camicasi is distinguished from R. linnaei by the non-tapering caudal widening of the spiracula. The male of R. sanguineus is distinguished from R. linnaei by shorter extension that does not taper into a long narrow extension of the spiracula. The genital pore atrium of female R. linnaei is broadly U-shaped, while it is a narrower U-shape in R. sanguineus. The remaining species within the R. sanguineus species complex - Rhipicephalus sulcatus Neumann, 1908, Rhipicephalus turanicus Pomerantsev, 1940, Rhipicephalus guilhoni Morel & Vassilades, 1963, Rhipicephalus secundus Feldman-Muhsam, 1952 and Rhipicephalus afranicus Bakkes, 2020, all exhibit spiracula with the dorsal prolongation as wide as the adjacent festoon. The DNA sequence of R. linnaei is most closely related to R. guilhoni. The phylogenetic analysis of mitogenome (mtDNA) sequences including assembled mtDNA from whole genome sequencing of the neotype supports R. linnaei as a well-defined taxon when compared with DNA sequences of other species of the R. sanguineus species complex, in particular: R. sanguineus, R. turanicus, R. secundus and R. camicasi. Molecularly, R. linnaei belongs to the so-called R. sanguineus s.l. "tropical lineage" distributed globally including the Americas, Africa, Europe, Asia and is the only species from R. sanguineus species complex in Australia.

Museum material of Rhipicephalus sanguineus sensu Roberts (1965) collected in 1902-1964 from Australia is identical to R. sanguineus sensu lato tropical lineage at the mitochondrial DNA 12S rRNA level

Ticks identified as Rhipicephalus sanguineus (Latreille, 1806) have been recorded in Australia since 1896. It is now recognized that ticks identified as R. sanguineus belong to different lineages. Recently, the so-called temperate lineage has been redescribed as R. sanguineus sensu stricto with a designated neotype. In Australia, the evidence suggests that only R. sanguineus sensu lato tropical lineage exists. We present a genetic evaluation of R. sanguineus sensu Roberts (1965) from museum material that was evaluated or identified by Roberts. We evaluated 12 museum specimens collected between 1913 and 1964, from various locations around Australia at the molecular level. DNA isolation was successful for 4/12 specimens. All four museum specimens were 100% identical to each other and to the reference R. sanguineus s.l. tropical lineage. Measurements of morphologically significant structures for male and female museum and contemporary tick specimens were obtained. The morphologically significant structures revealed there was no significant difference (ANOVA, P > 0.05) between these groups of male and female ticks. This study updates and supplement the comprehensive descriptions provided by Roberts (1965), which genetically belong to R. sanguineus s.l. tropical lineage.

Oral pharmacokinetic profile of fipronil and efficacy against flea and tick in dogs

Fipronil (FIP) is an ectoparasiticide of the phenylpyrazole class, used in veterinary medicine in topical form. Supported by evidence of uncontrolled human exposure to FIP and environmental damage caused by commercially available formulations, its use by oral administration has become promising. The effectiveness of FIP against the flea Ctenocephalides felis felis and the tick Rhipicephalus sanguineus and its pharmacokinetics and main active metabolite, fipronil sulfone (SULF) were evaluated after single oral administration of tablets in three different doses (2, 4, and 6 mg/kg) in dogs. Through the plasma concentration curves, it was possible to observe that the FIP showed rapid absorption and metabolization and slow elimination. The values of C_max (β = 0.7653) and AUC_{0- t} (β = 0.3209) did not increase proportionally with increasing dose. At 48 h after treatment, doses of 4 mg/kg (AUC_{0- t}  = 442.39 ± 137.35 µg/ml*h) and 6 mg/kg (AUC_{0- t}  = 421.32 ± 102.84 µg/ml*h) provided 100% and 99% efficacy against fleas, and 95% and 98% against ticks, respectively. The estimated EC₉₀ of FIP +SULF was 1.30 µg/ml against C. felis felis and 2.16 µg/ml against R. sanguineus. The correlation between the FIP pharmacokinetic and efficacy data demonstrated its potential for oral administration in the form of tablets for the control of ectoparasites in dogs, as a safer alternative for animals, humans, and the environment, aligned with the One Health concept.

Molecular Detection of Tick-Borne Pathogens in Stray Dogs and Rhipicephalussanguineus sensu lato Ticks from Bangkok, Thailand

Canine tick-borne pathogens (CTBPs) such as Babesia vogeli, Ehrlichia canis, Anaplasma platys, Hepatozoon canis, and Mycoplasma haemocanis are important pathogens in dogs worldwide. Rhipicephalus sanguineus sensu lato, the main vector of several CTBPs, is the most common tick species found on dogs in Thailand. The present study identified CTBPs in dogs and ticks infested dogs. Samples (360 dog blood samples and 85 individual ticks) were collected from stray dogs residing in 37 temples from 24 districts in Bangkok and screened for CTBPs using molecular techniques. The most common CTBP found infecting dogs in this study was Ehrlichia canis (38.3%) followed by Mycoplasma haemocanis (34.2%), Hepatozoon canis (19.7%), Babesia vogeli (18.1%), and Anaplasma platys (13.9%), respectively. Furthermore, A. platys (22.4%) was the most common CTBP in ticks followed by M. haemocanis (18.8%), B. vogeli (9.4%), H. canis (5.9%), and E. canis (2.4%), respectively. The detection of CTBPs from the present study highlights the potential risk of infections that may occur in stray dogs and their ticks residing in Bangkok temples. These findings underline the importance of performing active surveys to understand the complexity of distributions of CTBPs in dogs and their ticks in Thailand.

The "tropical lineage" of the brown dog tick Rhipicephalus sanguineus sensu lato identified as Rhipicephalus linnaei ()

The brown dog tick (Rhipicephalus sanguineus) parasitises dogs. Over the past decade, two distinct lineages have been recognised - R. sanguineus sensu lato "temperate lineage" and R. sanguineus sensu lato "tropical lineage". The nominal taxon R. sanguineus (Latreille, 1806) was recently associated with the "temperate lineage". We here identify the "tropical lineage" as Rhipicephalus linnaei (Audouin, 1826) using material from Australia, where no other Rhipicephalus species parasitises dogs. Whole genome sequencing of R. linnaei from Australia, Fiji and Laos, and assembly of their complete mitochondrial DNA (~15 kb) confirms the genetic identity and distinctness from all other known species within the brown dog tick species complex. Designation of the species R. linnaei is unequivocally supported by material available through the Australian National Insect Collection, Australia. Accordingly, we are formally justified in using R. linnaei for the "tropical lineage".

Genetic Diversity of Hard Ticks (Acari: Ixodidae) in the South and East Regions of Kazakhstan and Northwestern China

To date, there is no report on the genetic diversity of ticks in these regions. A total of 370 representative ticks from the south and east regions of Kazakhstan (SERK) and Xinjiang Uygur Autonomous Region (XUAR) were selected for molecular comparison. A fragment of the mitochondrial cytochrome c oxidase subunit I (cox1) gene, ranging from 631 bp to 889 bp, was used to analyze genetic diversity among these ticks. Phylogenetic analyses indicated 7 tick species including Hyalomma asiaticum, Hyalomma detritum, Hyalomma anatolicum, Dermacentor marginatus, Rhipicephalus sanguineus, Rhipicephalus turanicus and Haemaphysalis erinacei from the SERK clustered together with conspecific ticks from the XUAR. The network diagram of haplotypes showed that i) Hy. asiaticum from Almaty and Kyzylorda Oblasts together with that from Yuli County of XUAR constituted haplogroup H-2, and the lineage from Chimkent City of South Kazakhstan was newly evolved; and ii) the R. turanicus ticks sampled in Israel, Almaty, South Kazakhstan, Usu City, Ulugqat and Baicheng Counties of XUAR were derivated from an old lineage in Alataw City of XUAR. These findings indicate that: i) Hy. asiaticum, R. turanicus and Ha. erinacei shared genetic similarities between the SERK and XUAR; and ii) Hy. marginatum and D. reticulatus show differences in their evolution.