Detection of ehrlichial DNA in Haemaphysalis ticks recovered from dogs in Japan that is closely related to a novel Ehrlichia sp. found in cattle ticks from Tibet, Thailand, and Africa

Prevalence of Ehrlichia spp. in dogs and ticks in Hainan Province, China

BACKGROUND

Ehrlichia spp. are a group of intracellular parasitic bacteria primarily transmitted by ticks. They exhibit a wide global distribution and can infect a diverse range of mammals, including humans, underscoring their immense public health significance.

RESULTS

Among 631 ticks examined, all were identified as belonging to the Rhipicephalus linnaei; of these, 63 (9.98%) out of 631 ticks tested positive for Ehrlichia canis.Additionally, 140 (11.08%) out of 1264 dog blood samples were positive for E. canis. Notably, Ehrlichia ewingii and Ehrlichia chaffeensis were not detected. The prevalence of Ehrlichia infection in dogs was associated with factors such as age, breed, dewormer use, tick infestation, and living environment while displaying no association with the dog's gender.

CONCLUSIONS

In Hainan Province, Rhipicephalus linnaei is the dominant tick species infecting dogs. Dogs are vulnerable to Ehrlichia infection, particularly rural and stray dogs, suggesting the need for a targeted control strategy.

Bacterial blood microbiome of Mastomys rodents: implications for disease spill-over at the animal-human interface within the Bushbuckridge-East community, South Africa

The Bushbuckridge-East community in Mpumalanga Province, South Africa is bordered by nature reserves, including the Manyeleti Game Reserve. Murid rodents are prevalent in both Manyeleti and communal rangelands adjoining the community households. Although rodents are reservoir hosts for a broad range of viral, bacterial and parasitic pathogens, the rodent microbial diversity and transmission of zoonotic agents to humans in the community is understudied. In this study we investigated bacterial diversity in wild and commensal rodents sampled from different habitats. The 16S rRNA gene was amplified from DNA extracted from the blood of 24 wild Mastomys and one Steatomys sp. and subjected to PacBio circular consensus sequencing. As Bartonella species were dominant in the blood microbiome, gltA gene characterization was performed to delineate species. Rodents sampled from peri-urban and communal rangelands had higher proportions of Bartonella spp. [Hlalakahle (77.7%), Gottenburg (47.8%), Tlhavekisa (83.8%)] compared to those from the protected habitat (43.8%). Ehrlichia spp., Anaplasma spp., and Coxiella burnetii were detected at <1% of the sequence reads. Conventional PCR and sequencing validated the detection of Bartonella spp. with the first confirmation of Bartonella mastomydis infection in Mastomys in South Africa. Additionally, 317 mites, 90 fleas, 10 ticks and eight lice were collected from the rodents, providing evidence of possible vectors of the organisms detected. The detection of zoonotic agents in rodents in Bushbuckridge-East community, together with prior serological confirmation of Bartonella and Coxiella in non-malarial acute febrile patients from this community, highlights the possible risks that commensal rodents pose to human health.

Molecular characterization of Ehrlichia canis from naturally infected dogs reveals a novel Asiatic-lineage and co-circulation of multiple lineages in India

Canine monocytic ehrlichiosis caused by Ehrlichia canis is an important rickettsial pathogen of dogs transmitted by Rhipicephalus sanguineus sensu lato ticks in India. Globally, molecular characterization of E. canis is done using different E. canis gene targets. This study aimed to characterize genetic diversity of uncultured Ehrlichia species from dogs by 16S rRNA and partial gp200 gene (termed as p43 region) sequences data. Phylogeny based on 16S rRNA gene did not reveal any region-specific lineages. The phylogeny based on 5' region of E. canis gp200 gene (termed as p43 region) revealed four major clusters (A, B, C and D) and the Indian isolates fall under clusters A and B. Cluster A is characterized by an insertion of unique 141 bp tandem repeat sequence. Similar tandem repeat sequence was found in one of the E canis isolates from east-Asia, suggesting a possible divergence within this species. The study shows evidence for divergence of a new lineage within E. canis. The location of this insertion at the 'ankyrin repeat domains' containing region is suggestive of its possible role in modulation of host responses.

Opening the Black Box of Host Range, Vectorial Diversity, and Genetic Variants of Genus Anaplasma: The Contributing Factors Toward Its Zoonosis

Background: Genus Anaplasma of the family Anaplasmataceae possesses bacteria of hematopoietic origin, which are obligate intracellular Gram-negative bacteria transmitted mainly by tick vectors. The members of this group of infectious agents are not new as etiological agents of animal diseases worldwide. However, now, reports of their zoonotic potential have gained currency to study these pathogens. The emergence of new species of Anaplasma and the spread of existing species to new areas and hosts highlight the importance of monitoring and improving diagnostic and treatment options for zoonotic diseases caused by Anaplasma. Conclusion: This review focuses on the general and distinctive characteristics of Anaplasma spp., with particular emphasis on the novel species and their diverse spectrum of hosts as potential risk factors impacting its emerging zoonosis.

Ehrlichiosis in Dogs: A Comprehensive Review about the Pathogen and Its Vectors with Emphasis on South and East Asian Countries

Ehrlichiosis in dogs is an emerging vector borne rickettsial zoonotic disease of worldwide distribution. In general, three Ehrlichial species (Ehrlichia canis, E. ewingii, and E. chaffeensis) are involved in infecting dogs. Among them, E. canis is the well-known etiological pathogen affecting platelets, monocytes, and granulocytes. Dogs act as a reservoir, while the main vector responsible for disease transmission is Rhipicephalus sanguineus. However, in east Asian countries, Haemaphysalis longicornis is considered the principal vector for disease transmission. This disease affects multiple organs and systems and has three clinical manifestations, including acute, subclinical, and chronic. Definitive diagnosis involves visualization of morulae on cytology, detection of antibodies through an indirect immunofluorescence test (IFAT), and DNA amplification by polymerase chain reaction (PCR). In canine ehrlichiosis, no predilection of age or sex is observed; however, Siberian Huskies and German Shepherds are more likely to develop severe clinical manifestations. Doxycycline, rifampicin, and minocycline are proven to be effective drugs against canine ehrlichiosis. This review is intended to describe a brief overview of Ehrlichia infection in dogs, its reported prevalence in east and south Asian countries, and the latest knowledge regarding chemotherapy and associated vectors responsible for the disease transmission. This manuscript also identifies the prevailing knowledge gaps which merit further attention by the scientific community.

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

Epidemiological study of Kabuto Mountain virus, a novel uukuvirus, in Japan

Kabuto Mountain virus (KAMV), the new member of the genus Uukuvirus, was isolated from the tick Haemaphysalis flava in 2018 in Japan. To date, there is no information on KAMV infection in human and animals. Therefore, serological surveillance of the infection among humans and wild mammals was conducted by virus-neutralization (VN) test and indirect immunofluorescence assay (IFA). Sera of 24 humans, 59 monkeys, 171 wild boars, 233 Sika deer, 7 bears, and 27 nutria in Yamaguchi Prefecture were analyzed by VN test. The positive ratio of humans, monkeys, wild boars, and Sika deer were 20.8%, 3.4%, 33.9% and 4.7%, respectively. No positive samples were detected in bears and nutria. The correlation coefficients between VN test and IFA in human, monkey, wild boar, and Sika deer sera were 0.5745, 0.7198, 0.9967 and 0.9525, respectively. In addition, KAMV was detected in one pool of Haemaphysalis formosensis ticks in Wakayama Prefecture. These results indicated that KAMV or KAMV-like virus is circulating among many wildlife and ticks, and that this virus incidentally infects humans.

Diversity unearthed by the estimated molecular phylogeny and ecologically quantitative characteristics of uncultured Ehrlichia bacteria in Haemaphysalis ticks, Japan

Ehrlichia species are obligatory intracellular bacteria transmitted by arthropods, and some of these species cause febrile diseases in humans and livestock. Genome sequencing has only been performed with cultured Ehrlichia species, and the taxonomic status of such ehrlichiae has been estimated by core genome-based phylogenetic analysis. However, many uncultured ehrlichiae exist in nature throughout the world, including Japan. This study aimed to conduct a molecular-based taxonomic and ecological characterization of uncultured Ehrlichia species or genotypes from ticks in Japan. We first surveyed 616 Haemaphysalis ticks by p28-PCR screening and analyzed five additional housekeeping genes (16S rRNA, groEL, gltA, ftsZ, and rpoB) from 11 p28-PCR-positive ticks. Phylogenetic analyses of the respective genes showed similar trees but with some differences. Furthermore, we found that V1 in the V1-V9 regions of Ehrlichia 16S rRNA exhibited the greatest variability. From an ecological viewpoint, the amounts of ehrlichiae in a single tick were found to equal approx. 6.3E+3 to 2.0E+6. Subsequently, core-partial-RGGFR-based phylogenetic analysis based on the concatenated sequences of the five housekeeping loci revealed six Ehrlichia genotypes, which included potentially new Ehrlichia species. Thus, our approach contributes to the taxonomic profiling and ecological quantitative analysis of uncultured or unidentified Ehrlichia species or genotypes worldwide.

Molecular Characterization of Haemaphysalis Species and a Molecular Genetic Key for the Identification of Haemaphysalis of North America

Haemaphysalis longicornis (Acari: Ixodidae), the Asian longhorned tick, is native to East Asia, but has become established in Australia and New Zealand, and more recently in the United States. In North America, there are other native Haemaphysalis species that share similar morphological characteristics and can be difficult to identify if the specimen is damaged. The goal of this study was to develop a cost-effective and rapid molecular diagnostic assay to differentiate between exotic and native Haemaphysalis species to aid in ongoing surveillance of H. longicornis within the United States and help prevent misidentification. We demonstrated that restriction fragment length polymorphisms (RFLPs) targeting the 16S ribosomal RNA and the cytochrome c oxidase subunit I (COI) can be used to differentiate H. longicornis from the other Haemaphysalis species found in North America. Furthermore, we show that this RFLP assay can be applied to Haemaphysalis species endemic to other regions of the world for the rapid identification of damaged specimens. The work presented in this study can serve as the foundation for region specific PCR-RFLP keys for Haemaphysalis and other tick species and can be further applied to other morphometrically challenging taxa.

Upscaling the Surveillance of Tick-borne Pathogens in the French Caribbean Islands

Despite the high burden of vector-borne disease in (sub)tropical areas, few information are available regarding the diversity of tick and tick-borne pathogens circulating in the Caribbean. Management and control of vector-borne disease require actual epidemiological data to better assess and anticipate the risk of (re)emergence of tick-borne diseases in the region. To simplify and reduce the costs of such large-scale surveys, we implemented a high-throughput microfluidic real-time PCR system suitable for the screening of the main bacterial and parasitic genera involved in tick-borne disease and potentially circulating in the area. We used the new screening tool to perform an exploratory epidemiological study on 132 adult specimens of Amblyomma variegatum and 446 of Rhipicephalus microplus collected in Guadeloupe and Martinique. Not only the system was able to detect the main pathogens of the area-Ehrlichia ruminantium, Rickettsia africae, Anaplasma marginale, Babesia bigemina and Babesia bovis-but the system also provided evidence of unsuspected microorganisms in Caribbean ticks, belonging to the Anaplasma, Ehrlichia, Borrelia and Leishmania genera. Our study demonstrated how high-throughput microfluidic real-time PCR technology can assist large-scale epidemiological studies, providing a rapid overview of tick-borne pathogen and microorganism diversity, and opening up new research perspectives for the epidemiology of tick-borne pathogens.

Bacterial community profiling highlights complex diversity and novel organisms in wildlife ticks

Ticks Acari:Ixodida transmit a greater variety of pathogens than any other blood-feeding group of arthropods. While numerous microbes have been identified inhabiting Australian Ixodidae, some of which are related to globally important tick-borne pathogens, little is known about the bacterial communities within ticks collected from Australian wildlife. In this study, 1,019 ticks were identified on 221 hosts spanning 27 wildlife species. Next-generation sequencing was used to amplify the V1-2 hypervariable region of the bacterial 16S rRNA gene from 238 ticks; Amblyomma triguttatum (n = 6), Bothriocroton auruginans (n = 11), Bothriocroton concolor (n = 20), Haemaphysalis bancrofti (n = 10), Haemaphysalis bremneri (n = 4), Haemaphysalis humerosa (n = 13), Haemaphysalis longicornis (n = 4), Ixodes antechini (n = 29), Ixodes australiensis (n = 26), Ixodes fecialis (n = 13), Ixodes holocyclus (n = 37), Ixodes myrmecobii (n = 1), Ixodes ornithorhynchi (n = 10), Ixodes tasmani (n = 51) and Ixodes trichosuri (n = 3). After bioinformatic analyses, over 14 million assigned bacterial sequences revealed the presence of recently described bacteria 'Candidatus Borrelia tachyglossi', 'Candidatus Neoehrlichia australis', 'Candidatus Neoehrlichia arcana' and 'Candidatus Ehrlichia ornithorhynchi'. Furthermore, three novel Anaplasmataceae species were identified in the present study including; a Neoehrlichia sp. in I. australiensis and I. fecialis collected from quenda (Isoodon fusciventer) (Western Australia), an Anaplasma sp. from one B. concolor from echidna (Tachyglossus aculeatus) (New South Wales), and an Ehrlichia sp. from a single I. fecialis parasitising a quenda (WA). This study highlights the diversity of bacterial genera harboured within wildlife ticks, which may prove to be of medical and/or veterinary importance in the future.

Ecology of Bats, Their Ectoparasites, and Associated Pathogens on Saint Kitts Island

Ectoparasites of bats and bat-associated pathogens are poorly studied in the Lesser Antilles Islands. We report on an 11-mo field study on Saint Kitts Island of bat populations, their associated ectoparasites, and pathogens. We report on five ectoparasite species, including four Streblidae (Diptera) and a Spinturnicidae (Acari). Several genotypes of unnamed Bartonella were isolated from bats and ectoparasites. Microfilaria of an undetermined Litomosoides spp. were detected in blood from Artibeus jamaicensis Leach (Chiroptera: Phyllostomidae) (and associated ectoparasites: Trichobius intermedius Peterson and Hurka (Diptera: Streblidae) and Periglischrus iheringi Oudemans (Acari: Spinturnicidae)). In addition, an Ehrlichia sp. and Rickettsia africae were detected in the blood of several bat species. Our study is one of the first surveys of ectoparasite-borne pathogens in wild mammals from St. Kitts.

Molecular-genetic and ultrastructural characteristics of 'Candidatus Ehrlichia khabarensis', a new member of the Ehrlichia genus

Recently, a new Ehrlichia genetic variant, Ehrlichia sp. Khabarovsk, was identified in tissue samples of small mammals captured in the Russian Far East. To further characterize Ehrlichia sp. Khabarovsk, tissue homogenate from a naturally infected gray red-backed vole (Myodes rufocanus) was passaged three times in newborn laboratory mice. Using nested PCR Ehrlichia sp. Khabarovsk DNA was detected in tissue samples from infected mice at 1-4 weeks post inoculation. Electron microscopic examination revealed morulae containing gram-negative bacterial cells in monocytes of mouse spleen and liver. The size and ultrastructure of these cells corresponded to those described previously and allowed us to identify the bacteria as Ehrlichia sp. The comparison of ehrlichial 16S rRNA, groEL and gltA genes and putative GroEL and GltA amino acid sequences has demonstrated that Ehrlichia sp. Khabarovsk, like Ehrlichia ruminantium, is more distant from all other Ehrlichia species than these species are between themselves. Phylogenetic analysis has shown that Ehrlichia sp. Khabarovsk belongs to the clade formed by Ehrlichia spp. but clusters separately from other Ehrlichia species and genetic variants. These data indicate that Ehrlichia sp. Khabarovsk can be considered as a new candidate species. We propose to designate it as 'Candidatus Ehrlichia khabarensis' according to the territory where this species was found.

Molecular investigation of tick-borne pathogens in ticks from grazing cattle in Korea

This study was carried out to identify the tick species that infest grazing cattle and to determine the presence of tick-borne pathogens transmitted by these ticks in Korea. A total of 903 ticks (categorized into 566 tick pools) were collected from five provinces during 2010-2011. The most prevalent tick species was Haemaphysalis longicornis, followed by three Ixodes spp. ticks. The collected ticks were infected with both rickettsial and protozoan pathogens. In all, 469 (82.9%) tick pools tested positive for the Anaplasma/Ehrlichia 16S rRNA gene, whereas 67 (11.8%) were positive for the Babesia/Theileria 18S rRNA gene. Among the rickettsial pathogens, E. canis was detected with the highest rate (22.3%), followed by A. platys (20%), E. chaffeensis (19.4%), E. ewingii (19.3%), Rickettsia sp. (12.4%), A. phagocytophilum (5.5%) and E. muris (0.5%). Among the protozoan pathogens, T. equi was detected with the highest rate (7.2%), followed by T. sergenti/T. buffeli (3.7%) and B. caballi (0.35%). Simultaneous infections with up to seven pathogens were also identified. In particular, ticks infected with rickettsial pathogens were also infected with protozoan pathogens (22 samples). All five provinces investigated infected with tick-borne pathogens.

Detection of the new Ehrlichia species closely related to Ehrlichia ewingii from Haemaphysalis longicornis in Yonaguni Island, Okinawa, Japan

We collected a total of 206 Haemaphysalis longicornis ticks by flagging in pastures in Yonaguni Island, Okinawa, Japan, in April 2008. Four of the 206 tick DNA samples tested were positive in a polymerase chain reaction (PCR) screening for the 16SrRNA gene of Anaplasmataceae. Partial sequences of 4 PCR products were identical to each other. Longer sequences of the 16SrRNA gene were successfully determined in 2 of the 4 tick samples, and the obtained 1,392 bp and 1,300 bp sequences revealed high similarity to the 16SrRNA gene sequences of the validated Ehrlichia species, including Ehrlichia ewingii, E. chaffeensis, and E. canis (98.3-98.6%). We also sequenced 1,304 bp of the groEL gene from the 2 tick samples, and found that these had the highest similarity to sequences of E. ewingii (94.0-94.4%) in the validated ehrlichial species. Based on the 16SrRNA and groEL gene sequences, the ehrlichial agents detected in this study were similar to the Ehrlichia species detected in Asia and may compose a new Ehrlichia species with other Ehrlichia species detected in Asia.

Presence of a novel Ehrlichia sp. in Ixodes granulatus found in Okinawa, Japan

Ehrlichia-specific DNA fragments of Ehrlichia omp-1 and groEL genes were found in two I. granulatus ticks which had been collected from wild small mammals in a subtropical zone in Japan. The DNA sequences of groEL and 16SrDNA of the suspected Ehrlichia were clustered into a group of E. chaffeensis, E. muris, and Ehrlichia sp. HF565 found in I. ovatus, but were distinctly different. Therefore the Ehrlichia strain was designated as a novel Ehrlichia sp. 360. The Ehrlichia sp. 360 was detected in I. granulatus but not in any other ticks. This suggests that I. granulatus is a probable vector of Ehrlichia sp. 360 in Japan.

Microbial pathogens in ticks, rodents and a shrew in northern Gyeonggi-do near the DMZ, Korea

A total of 1,618 ticks [420 individual (adults) and pooled (larvae and nymphs) samples], 369 rodents (Apodemus agrarius, Rattus norvegicus, Tscherskia triton, Mus musculus, and Myodes regulus), and 34 shrews (Crocidura lasiura) that were collected in northern Gyeonggi-do near the Demilitarized Zone (DMZ) of Korea during 2004-2005, were assayed by PCR for selected zoonotic pathogens. From a total of 420 individual and pooled tick DNA samples, Anaplasma (A.) phagocytophilum (16), A. platys (16), Ehrlichia (E.) chaffeensis (63), Borrelia burgdorferi (16), and Rickettsia spp. (198) were detected using species-specific PCR assays. Out of 403 spleens from rodents and shrews, A. phagocytophilum (20), A. platys (34), E. chaffeensis (127), and Bartonella spp. (24) were detected with species-specific PCR assays. These results suggest that fevers of unknown causes in humans and animals in Korea should be evaluated for infections by these vector-borne microbial pathogens.

Detection of Borrelia garinii, Borrelia tanukii and Borrelia sp. closely related to Borrelia valaisiana in Ixodes ticks removed from dogs and cats in Japan

Ticks removed from 1136 dogs and 134 cats all over Japan were examined for Borrelia infection by PCR and sequencing. The 5S-23S rDNA intergenic spacer of Borrelia was detected from two Ixodes persulcatus ticks from two dogs and two unidentified Ixodes spp. from another two dogs in Hokkaido, and two Ixodes granulatus ticks from two cats in Okinawa. Additional 2 I. granulatus from the same cats also showed positive. Sequence analysis of the PCR products revealed that the one from Hokkaido was similar to B. garinii, the three from Hokkaido to B. tanukii, and the four from Okinawa to a novel Borrelia sp. closely related to B. valaisiana. The data was confirmed by analysis of the flagellin gene sequence. Infected ticks carried by companion animals can be introduced into the human environment.

Tick-borne rickettsial pathogens in ticks and small mammals in Korea

In order to investigate the prevalence of tick-borne infectious agents among ticks, ticks comprising five species from two genera (Hemaphysalis spp. and Ixodes spp.) were screened using molecular techniques. Ticks (3,135) were collected from small wild-caught mammals or by dragging/flagging in the Republic of Korea (ROK) and were pooled into a total of 1,638 samples (1 to 27 ticks per pool). From the 1,638 tick samples, species-specific fragments of Anaplasma phagocytophilum (1 sample), Anaplasma platys (52 samples), Ehrlichia chaffeensis (29 samples), Ehrlichia ewingii (2 samples), Ehrlichia canis (18 samples), and Rickettsia rickettsii (28 samples) were amplified by PCR assay. Twenty-one pooled and individual tick samples had mixed infections of two (15 samples) or three (6 samples) pathogens. In addition, 424 spleen samples from small captured mammals (389 rodents, 33 insectivores, and 2 weasels) were screened for selected zoonotic pathogens. Species-specific DNA fragments of A. phagocytophilum (110 samples), A. platys (68 samples), E. chaffeensis (8 samples), E. ewingii (26 samples), E. canis (51 samples), and Rickettsia sp. (22 samples) were amplified by PCR assay. One hundred thirty small mammals had single infections, while 4, 14, and 21 striped field mice (Apodemus agrarius) had mixed infections of four, three, and two pathogens, respectively. Phylogenetic analysis based on nucleotide sequence comparison also revealed that Korean strains of E. chaffeensis clustered closely with those from China and the United States, while the Rickettsia (rOmpA) sequences clustered within a clade together with a Chinese strain. These results suggest that these agents should be considered in differential diagnosis while examining cases of acute febrile illnesses in humans as well as animals in the ROK.

Serological evidence of infection of Anaplasma and Ehrlichia in domestic animals in Xinjiang Uygur Autonomous Region area, China

Serological methods were utilized to detect Anaplasma and Ehrlichia infection in domestic animals in Xinjiang Uygur Autonomous Region, China. By using an indirect immunofluorescence assay (IFA), antibodies that reacted with Anaplasmaphagocytophilum and Ehrlichiachaffeensis were detected mainly in ruminants kept on pastureland in Altai, Ili and Kashgar area. Antibody titers up to 1:320 were recorded. These results indicate that ruminants kept in these areas may be infected with some species of Anaplasma and Ehrlichia.