Large-Scale Survey for Tickborne Bacteria, Khammouan Province, Laos

Molecular identification of tick (Acari: Ixodidae) and tick-borne pathogens from Przewalski's gazelle (Procapra Przewalskii) and Tibetan sheep (Ovis aries) in Qinghai Lake National Nature Reserve, China

The Qinghai Lake National Nature Reserve (QLNNR), renowned for its abundant natural resources and diverse ecological habitats, serves as an ideal environment for ticks, thereby increasing the risk of various tick-borne pathogens (TBPs) transmission. This study aimed to investigate the prevalence of TBPs in ticks collected from Przewalski's gazelle and Tibetan sheep within the QLNNR. A total of 313 tick samples were collected from the vicinity of Qinghai Lake. Tick species identification was conducted using both morphological and molecular biology techniques. Polymerase chain reaction (PCR) amplification was performed to detect the presence of spotted fever group (SFG) Rickettsia, Coxiella burnetii, Anaplasma phagocytophilum, Babesia microti, Theileria spp, Borrelia burgdorferi, Brucella spp, and Anaplasma ovis was performed using specific primers. Positive samples were sequenced and analyzed using BLASTn, followed by phylogenetic tree construction. The ticks collected from the Qinghai Lake area were identified as Dermacentor nuttalli. The overall prevalence rates of ticks carrying SFG Rickettsia and C. burnetii were 42.8 % (134/313) and 4.8 % (15/313), respectively. Three SFG Rickettsia species were detected, including R. raoultii 33.9 % (106/313), R. slovaca 3.8 % (12/113) and R. sibirica 7.7 % (24/113), with R. raoultii being the predominant species. The prevalence rates of SFG Rickettsia and C. burnetii in ticks from Tibetan sheep was 44.7 % (115/257) and 4.7 % (12/257), respectively,and in ticks from Przewalski's gazelle were 33.9 % (19/56) and 5.4 % (3/56). Furthermore, the study revealed a positive linear relationship between the abundance of Przewalski's gazelle and the number of ticks, as well as the prevalence of TBPs. The current study has identified Dermacentor nuttalli as the predominant tick vector species within the QLNNR region. The detection of SFG Rickettsia and C. burnetii has augmented our understanding of the epidemiological profile of ticks and TBPs in this area, thereby providing a robust theoretical foundation for the implementation of effective prevention and control strategies against TBPs.

Flea-Borne Rickettsioses and Scrub Typhus in Patients with Suspected Arbovirus Infection in Bangkok, Thailand

Background: In urban Thailand, arboviral infections dominate diagnoses of acute undifferentiated fevers (AUFs) owing to their well-defined epidemiology and characteristic clinical presentations. However, rickettsial diseases, also endemic in this setting, remain under-recognized owing to challenges in early detection. Objective: This study aimed to identify potential rickettsial infections among patients with AUF in Bangkok and vicinity utilizing leftover nucleic acid extracted from serum samples from patients initially suspected of but negative for arbovirus infections. Materials and Methods: A total of 609 nucleic acid samples were screened for rickettsial bacteria using real-time PCR, targeting the 17-kDa common antigen gene of Rickettsia spp. and the 47-kDa gene of Orientia tsutsugamushi. Results: Nine samples were positive for Rickettsia spp. and two were positive for O. tsutsugamushi. DNA sequence and phylogenetic analyses based on partial 17-kDa antigen and citrate synthase (gltA) genes identified the Rickettsia-positive samples as R. typhi in eight cases and R. felis in one case. Analysis of the 56-kDa type-specific antigen gene identified the two O. tsutsugamushi isolates as Gilliam-related genotypes. Although rickettsial diseases typically present with mild symptoms, two patients with R. typhi infection (murine typhus) developed respiratory distress syndrome, highlighting the potential for rare but serious complications. Conclusion: This study underscores the critical importance of differential diagnosis and prompt, effective intervention to prevent complications in suspected cases.

Molecular detection of Rickettsia species in ectoparasites collected from two southern provinces of Cambodia

Arthropod-borne rickettsioses comprise a wide variety of subtypes that are endemic in Cambodia, but there remains very little data on the geographic distribution of the pathogens or their vectors. Surveys were conducted in Koh Kong and Preah Sihanouk Provinces between September 2017 and June 2018 to collect ectoparasites from peridomestic animals and the environment using dragging and flagging methods. Collected ectoparasites were sorted and identified morphologically, then pooled by species, host, and location for molecular detection using Rickettsia genus- and species-specific qPCR and/or multilocus sequence typing (MLST) assays. A total of 14,254 ectoparasites were collected including seven new locality records. Rickettsia species were detected in 35.5% (174/505) of the pools screened representing 3,149 randomly selected ectoparasites from the total collected. Rickettsia asembonensis was detected in 89.6% (147/164) of Rickettsia-positive flea pools and 3.6% (6/164) of the flea pools were positive for both R. asembonensis and Rickettsia felis. Candidatus Rickettsia senegalensis from Ctenocephalides orientis fleas and Rickettsia sp. close to Rickettsia japonica and Rickettsia heilongjiangensis from Haemaphysalis ticks were identified by MLST. This appears to be the first report of these new ectoparasite records and rickettsial species in southern Cambodia, suggesting a potential health risk to military and civilians in this region.

Challenges for ticks and tick-borne diseases research in Southeast Asia: Insight from the first international symposium in Cambodia

BACKGROUND

Ticks, as critical vectors of a variety of pathogens, pose a significant public health challenge globally. In Southeast Asia (SEA), ticks are responsible for transmitting a diverse array of pathogens affecting humans and animals. The geographical and ecological diversity of SEA provides a unique environment that supports a wide range of tick species, which complicates the management and study of tick-borne diseases (TBDs).

METHODOLOGY/PRINCIPAL FINDINGS

This article synthesizes findings from the first international symposium on ticks and TBDs in Southeast Asia, held in Phnom Penh on June 22 and 23, 2023. It highlights regional efforts to understand tick ecology and pathogen transmission. This paper proposes to present a summary of the various presentations given during the symposium following 3 main parts. The first one is devoted to the state of knowledge regarding ticks and TBDs in SEA countries, with presentations from 6 different countries, namely Cambodia, Indonesia, Laos, Malaysia, Thailand, and Vietnam. The second part focuses on the development of new research approaches on tick-borne pathogens (TBPs) and TBDs. The last part is a summary of the round table discussion held on the final day, with the aim of defining the most important challenges and recommendations for researches on TBP and TBD in the SEA region.

CONCLUSIONS/SIGNIFICANCE

Key topics discussed include advancements in diagnostic tools, such as MALDI-TOF MS and proteomics, and the development of sustainable strategies for tick management and disease prevention. The symposium facilitated the exchange of knowledge and collaborative networks among experts from various disciplines, promoting a unified approach to tackling TBDs in the region. The symposium underscored the need for enhanced surveillance, diagnostics, and inter-regional cooperation to manage the threat of TBDs effectively. Recommendations include the establishment of a regional database for tick identification and the expansion of vector competence studies. These initiatives are crucial for developing targeted interventions and understanding the broader implications of climate change and urbanization on the prevalence of TBDs.

Dermacentor (Indocentor) auratus Supino 1897: Potential geographic range, and medical and veterinary significance

Dermacentor (Indocentor) auratus Supino, 1897 occurs in many regions of Southeast Asia and South Asia. In many regions of Southeast Asia and South Asia, targeted tick sampling and subsequent screening of collected D. auratus ticks have detected pathogenic bacteria and viruses in D. auratus. These disease-causing pathogens that have been detected in D. auratus include Anaplasma, Bartonella, Borrelia, Rickettsia (including spotted fever group rickettsiae), African swine fever virus, Lanjan virus, and Kyasanur forest disease virus. Although D. auratus predominantly infests wild pigs, this tick is also an occasional parasite of humans and other animals. Indeed, some 91 % of human otoacariasis cases in Sri Lanka were due to infestation by D. auratus. With the propensity of this tick to feed on multiple species of hosts, including humans, and the detection of pathogenic bacteria and viruses from this tick, D. auratus is a tick of medical, veterinary, and indeed zoonotic concern. The geographic range of this tick, however, is not well known. Therefore, in the present paper, we used the species distribution model, BIOCLIM, to project the potential geographic range of D. auratus, which may aid pathogen and tick-vector surveillance. We showed that the potential geographic range of D. auratus is far wider than the current geographic distribution of this tick, and that regions in Africa, and in North and South America seem to have suitable climates for D. auratus. Interestingly, in Southeast Asia, Borneo and Philippines also have suitable climates for D. auratus, but D. auratus has not been found in these regions yet despite the apparent close proximity of these regions to Mainland Southeast Asia, where D. auratus occurs. We thus hypothesize that the geographic distribution of D. auratus is largely dependent on the movement of wild pigs and whether or not these wild pigs are able to overcome dispersal barriers. We also review the potential pathogens and the diseases that may be associated with D. auratus and provide an updated host index for this tick.

Molecular Survey of Rickettsia raoultii in Ticks Infesting Livestock from Pakistan with Notes on Pathogen Distribution in Palearctic and Oriental Regions

Ticks are hematophagous ectoparasites that transmit different pathogens such as Rickettsia spp. to domestic and wild animals as well as humans. Genetic characterizations of Rickettsia spp. from different regions of Pakistan are mostly based on one or two genetic markers and are confined to small sampling areas and limited host ranges. Therefore, this study aimed to molecularly screen and genetically characterize Rickettsia spp. in various tick species infesting camels, sheep, and goats. All the collected tick specimens were morphologically identified, and randomly selected tick species (148) were screened molecularly for the detection of Rickettsia spp. by amplifying three rickettsial DNA fragments, namely, the citrate-synthase gene (gltA), outer-membrane protein A (ompA), and outer-membrane protein B (ompB). After examining 261 hosts, 161 (61.7%) hosts were found infested by 564 ticks, including 287 (50.9%) nymphs, 171 (30.3%) females, and 106 (18.8%) males in five districts (Kohat, Dera Ismail Khan, Lower Dir, Bajaur, and Mansehra). The highest occurrence was noted for Hyalomma dromedarii (number = 72, 12.8%), followed by Haemaphysalis sulcata (n = 70, 12.4%), Rhipicephalus turanicus (n = 64, 11.3%), Rhipicephalus microplus (n = 55, 9.7%), Haemaphysalis cornupunctata (n = 49, 8.7%), Hyalomma turanicum (n = 48, 8.5%), Hyalomma isaaci (n = 45, 8.0%), Haemaphysalis montgomeryi (n = 44, 7.8%), Hyalomma anatolicum (n = 42, 7.5%), Haemaphysalis bispinosa (n = 38, 6.7%), and Rhipicephalus haemaphysaloides (n = 37, 6.6%). A subset of 148 ticks were tested, in which eight (5.4%) ticks, including four Hy. turanicum, two Ha. cornupunctata, one Ha. montgomeryi, and one Ha. bispinosa, were found positive for Rickettsia sp. The gltA, ompA, and ompB sequences revealed 100% identity and were phylogenetically clustered with Rickettsia raoultii reported in China, Russia, USA, Turkey, Denmark, Austria, Italy, and France. Additionally, various reports on R. raoultii from Palearctic and Oriental regions were summarized in this study. To the best of our knowledge, this is the first report regarding genetic characterization and phylogenetic analysis of R. raoultii from Pakistan. Further studies to investigate the association between Rickettsia spp. and ticks should be encouraged to apprise effective management of zoonotic consequences.

Rickettsia africae and other unclassified Rickettsia species of the spotted fever group in ticks of the Western Ghats, India

The spotted fever group (SFG) of Rickettsia are zoonotic disease-causing pathogens, commonly transmitted by hard ticks to a wide range of hosts, including humans. Rickettsia conorii is the common SFG recognised in India, whereas most of the infections due to other group species go undifferentiated at the species level. Hence, this study was conducted to screen host-seeking ticks in the Western Ghats region, India, for the DNA of SFG Rickettsia. The ticks were collected from Kerala, Goa, and Maharashtra states of India during a survey conducted between November 2017 and January 2018. In total, 288 tick pools were screened for Rickettsia spp. DNA using pan-Rickettsia real-time PCR, and conventional PCR targeting the gltA, OmpA and 17-kDa protein-coding genes. Nucleotide sequences were subjected to phylogenetic analysis using the NCBI BLAST tool to identify submitted sequences with higher homology. Neighbour-joining trees were constructed using the reference sequences of the GenBank database. Overall, Rickettsia spp. DNA was detected in 27.2% (62/228 pools) of host-seeking ticks across the Western Ghats region, with an estimated minimum infection rate of 0.057. Upon phylogenetic analysis, it was identified that the detected sequences were highly similar (> 99% sequence homology) to R. africae, Candidatus R. laoensis and an un-categorised Rickettsia species, and they were widely carried by Haemaphysalis ticks. The current study is the first report of R. africae and Candidatus R. laoensis in ticks in India. Although the pathogenicity of these species is not well documented, they may pose a potential threat to both animal and the human population in this geographical region.

A novel Rickettsia, Candidatus Rickettsia takensis, and the first record of Candidatus Rickettsia laoensis in Dermacentor from Northwestern Thailand

Three hundred and forty-four tick samples were collected from vegetation at Taksin Maharat National Park, Tak province, northwestern Thailand. They were morphologically identified and molecularly confirmed by 16S rRNA and COI genes as Dermacentor laothaiensis (n = 105), D. steini (n = 139), and D. auratus (n = 100). These ticks were examined for the spotted fever group rickettsiae (SFGRs) using PCR and DNA sequencing of six genes; 17-kDa, gltA, 16S rRNA, ompA, ompB, and sca4. Of these ticks, 6.10% (21/344) gave positive results for the presence of SFGRs. Phylogenetic analyses of the SFGRs clearly indicated that a novel genotype assigned as Candidatus Rickettsia takensis was detected in D. laothaiensis (19/105) and at lesser frequency in D. steini (1/139). Furthermore, Candidatus Rickettsia laoensis was also found at a low frequency in D. auratus (1/100), the first record in Thailand. Although, the pathogenicities of these SFGRs remain unknown, our findings suggest potential risks of SFGRs being transmitted via ticks near the border between Thailand and Myanmar, a gateway of daily migrations of local people and visitors both legal and illegal.

Metatranscriptomic profiling reveals diverse tick-borne bacteria, protozoans and viruses in ticks and wildlife from Australia

Tick-borne zoonoses are emerging globally due to changes in climate and land use. While the zoonotic threats associated with ticks are well studied elsewhere, in Australia, the diversity of potentially zoonotic agents carried by ticks and their significance to human and animal health is not sufficiently understood. To this end, we used untargeted metatranscriptomics to audit the prokaryotic, eukaryotic and viral biomes of questing ticks and wildlife blood samples from two urban and rural sites in New South Wales, Australia. Ixodes holocyclus and Haemaphysalis bancrofti were the main tick species collected, and blood samples from Rattus rattus, Rattus fuscipes, Perameles nasuta and Trichosurus vulpecula were also collected and screened for tick-borne microorganisms using metatranscriptomics followed by conventional targeted PCR to identify important microbial taxa to the species level. Our analyses identified 32 unique tick-borne taxa, including 10 novel putative species. Overall, a wide range of tick-borne microorganisms were found in questing ticks including haemoprotozoa such as Babesia, Theileria, Hepatozoon and Trypanosoma spp., bacteria such as Borrelia, Rickettsia, Ehrlichia, Neoehrlichia and Anaplasma spp., and numerous viral taxa including Reoviridiae (including two coltiviruses) and a novel Flaviviridae-like jingmenvirus. Of note, a novel hard tick-borne relapsing fever Borrelia sp. was identified in questing H. bancrofti ticks which is closely related to, but distinct from, cervid-associated Borrelia spp. found throughout Asia. Notably, all tick-borne microorganisms were phylogenetically unique compared to their relatives found outside Australia, and no foreign tick-borne human pathogens such as Borrelia burgdorferi s.l. or Babesia microti were found. This work adds to the growing literature demonstrating that Australian ticks harbour a unique and endemic microbial fauna, including potentially zoonotic agents which should be further studied to determine their relative risk to human and animal health.

Spotted Fever Group Rickettsia Infecting Ticks (Acari: Ixodidae), Yak (Bos grunniens), and Tibetan Sheep (Ovis aries) in the Qinghai–Tibetan Plateau Area, China

The Qinghai–Tibet Plateau Area (QTPA) has a complex natural ecosystem, causing a greatly increased risk of spreading various tick-borne diseases including rickettsial infections, which are regarded as one of the oldest known vector-borne zoonoses. However, the information of one of its pathogen, spotted fever group Rickettsia (SFG Rickettsia), is limited in tick vectors and animals in this area. Therefore, this study focused on the investigation of SFG Rickettsia in tick vectors, yaks (Bos grunniens), and Tibetan sheep (Ovis aries) in the QTPA. A total of 1,000 samples were collected from nine sampling sites, including 425 of yaks, 309 of Tibetan sheep, 266 of ticks. By morphological examination, PCR, and sequencing, we confirmed the species of all collected ticks. All tick samples, all yak and Tibetan sheep blood samples were detected based on SFG Rickettsia ompA and sca4 gene. The results showed that all tick samples were identified to be Haemaphysalis qinghaiensis, and the positive rates of SFG Rickettsia were 5.9% (25/425), 0.3% (1/309), and 54.1% (144/266) in yaks, Tibetan sheep, and ticks, respectively. All positive samples were sequenced, and BLASTn analysis of the ompA gene sequences of SFG Rickettsia showed that all positive samples from animals and ticks had 99.04–100% identity with yak and horse isolates from Qinghai Province, China. BLASTn analysis of the sca4 gene sequences of SFG Rickettsia showed that all positive samples had 97.60–98.72% identity with tick isolates from Ukraine. In addition, the phylogenetic analysis showed that all the SFG Rickettsia ompA and sca4 sequences obtained from this study belong to the same clade as Rickettsia raoultii isolated from livestock and ticks from China and other countries. Molecularly, this study detected and characterized SFG Rickettsia both in the tick vectors and animals, suggesting that the relationship between SFG Rickettsia, tick species and animal hosts should be explored to understand their interrelationships, which provide a theoretical basis for preventing control of this pathogen.

Cross-sectional seasonal prevalence and relative risk of ectoparasitic infestations of rodents in North Sinai, Egypt

Background and Aim:

Rodents are ubiquitous animals that host ectoparasites and transmit zoonotic diseases. We conducted a cross-sectional study on the seasonal variation, period prevalence (Pp), and relative risk of ectoparasitic infestations in rodents collected in North Sinai, Egypt, from September 2019 to August 2020.

Materials and Methods:

We captured 380 rodents during the study period. Rodents were euthanized to perform species identification, and 2930 external parasites were collected and identified using light microscopic examination with systemic keys depending on morphological characters.

Results:

Rattus norvegicus (brown rat), Rattus rattus frugivorus (white-bellied rat), Rattus rattus alexandrines (gray-bellied rat), and Mus musculusdomesticus (house mouse) were captured at the highest frequencies during summer (n=186), followed by spring (n=84), fall (n=71), and winter (n=39), with a higher proportion of males captured in all seasons. Analysis of the infestation Pp revealed highly significant increases (p<0.01) in ectoparasites during the winter. Temperature, humidity, and dew point were significantly (p<0.01) correlated with the numbers of captured and infested rodents. Parasitological examinations showed the higher risks of flea (Echidnophaga gallinacea, Xenopsylla cheopis, and Leptopsylla segnis) and lice (Hoplopleura hirsuta, Hoplopleura ocanthopus, Hoplopleura oenomydis, and Polyplax spinulosa) infestations during winter and mite (Laelaps nuttalli, Dermanyssus gallinae, Ornithonyssus bacoti, and Myobia musculi) infestations during summer.

Conclusion:

We conclude that ectoparasitic infestation prevalence and risk varies with predominating macroclimatic conditions. Strict preventive and biosecurity measures should be applied to combat rodent-related problems.

Seroepidemiological Study of Spotted Fever Group Rickettsiae and Identification of a Putative New Species, Rickesttsia sp. Da-1, in Gongliao, Northeast Taiwan

Tick-borne spotted fever group (SFG) rickettsioses were neglected in Taiwan. The study reported a seroepidemiological survey of SFG rickettsiae in residents in Gongliao District, Northeast Taiwan. Blood samples were examined for antibodies against SFG rickettsiae by enzyme-linked immunosorbent assay and immunofluorescence assay. Risk factors were assessed using logistic regression. Ticks parasitizing dogs were collected within a 2 km radius from the houses of seropositive participants, and PCR was performed to detect possible tick-borne pathogens. Of 1108 participants, 75 (6.8%) had antibodies against SFG rickettsiae. Residents were more likely to be seropositive if they were older than 65 years, recruited by Dr. Enjoy’s Clinic, or resided in Jilin village. A total of 184 ticks including 5 species (Rhipicephalus sanguineus, Rhipicephalus haemaphysaloides, Dermacentor auratus, Haemaphysalis hystricis, Haemaphysalis ornithophila) were collected. Rickettsia spp. were detected in 6.5% (12/184) of ticks. Rickettsia sp. TwKM01 was found in 6 R. sanguineus and 4 R. haemaphysaloides; while Rickettsia sp. TwKM03 was identified in 1 R. sanguineus. Moreover, gene-based pairwise analysis indicated identification of a putative new species, Rickettsia sp. Da-1, in D. auratus. These findings provided evidence of SFG rickettsiae infection in ticks and suggested SFG rickettsiae exposure in the residents.

Characterization of the complete mitochondrial genomes of two Ixodes ticks, I. nipponensis and Ixodes (Pholeoixodes) sp

In this study, the authors sequenced and characterized the complete mitochondrial (mt) genomes of two hard ticks of the genus Ixodes, I. nipponensis and Ixodes (Pholeoixodes) sp., which were 14 505 and 14 543 bp in length, respectively. Their mt genomes encoded 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA genes and two ribosomal RNA genes, and have only one non-coding region. The gene order in their mt genomes was the same as that of other Ixodes spp. mt genomes. The average sequence identity, combined nucleotide diversity, non-synonymous/synonymous substitutions ratio analyses consistently demonstrated that cox1, rrnS, cox2, cox3 and cytb were the most conserved and atp8, nad6 and nad2 were the most variable genes across Ixodes mitogenomes. Phylogeny of the present Ixodes spp., and other selected hard tick species, based on concatenated amino acid sequences of PCGs, confirmed their position within the genus Ixodes and sub-family Ixodinae. The novel mt markers described herein will be useful for further studies of the population genetics, molecular epidemiology and systematics of hard ticks.

The complete mitochondrial genome of Dermacentor (Indocentor) auratus (Acari, Ixodidae)

Dermacentor (Indocentor) auratus Supino, 1897 is a prominent ixodid vector of numerous pathogens of public health and veterinary importance. Using long-range PCR of two overlapping regions sequenced on an Illumina MiSeq machine, the complete mitochondrial genome of D. auratus is reported here. The resulting contigs were able to be assembled into a complete and circularised genome which had the general organisation of the mitochondrial genomes of the Metastriates. It had a total length of 14,766 bp and contained 37 genes, including 13 protein-coding genes, 22 transfer RNA genes, and 2 ribosomal RNA genes, as well as 2 non-coding control regions and 3 tick-boxes. The phylogenetic analysis on the whole mitogenome confirmed the position of D. auratus within the Dermacentor clade.

Screening of ectoparasites from domesticated dogs for bacterial pathogens in Vientiane, Lao PDR

Arthropod-borne diseases are widespread worldwide and are a complex interaction between animals, humans and ectoparasites. The understanding of the diversity and epidemiology of organisms transmitted by arthropod vectors, and the role of hosts and vectors in transmission of infections remain limited in Lao PDR. What knowledge does exist is primarily focused on more rural regions of the country. This study screened ectoparasites from domestic dogs in Vientiane city for the presence of bacterial pathogens of zoonotic importance. A total of 3,511 arthropod vectors were collected from 112 dogs. Vectors collected were Rhipicephalus sanguineus ticks, Ctenocephalides felis felis and Ctenocephalides felis orientis fleas and Heterodoxus spiniger lice. A sub-sample of vectors from each dog was analysed by PCR to identify the potential bacteria. From 129 vector pools, Rickettsia spp. was detected in 6.7% (7/105) pools of ticks, 86.4% (19/22) pools of fleas and both pools of lice. Sequencing analysis confirmed Rickettsia felis in 13 flea pools and one louse pool and Rickettsia asembonensis in six flea pools. Anaplasmataceae was identified in 14.3% (15/105) tick pools and 100% (22/22) flea pools. Sequencing revealed the presence of Anaplasma platys in ticks and Wolbachia pipientis in fleas. Leptospira spp. was detected in one tick and one louse pool, and Brucella spp. was detected in 12.4% (13/105) tick pools. All samples were negative for Bartonella spp., Coxiella burnetii and Borrelia burgdorferi. This is the first study providing evidence of R. asembonensis in fleas in Laos. Results from this study show arthropods are potential vectors to transmit zoonotic infection in Vientiane city, suggesting humans are at risk of zoonotic infections in the city.

Identification and molecular analysis of Ixodid ticks (Acari: Ixodidae) infesting wild boars (Sus scrofa) and tick-borne pathogens at the Meihua mountain of southwestern Fujian, China

Wildlife is essential to the biodiversity of the Meihua mountain, southwestern Fujian province, China. However, there have been few surveys of the distribution of ixodid ticks (Acari: Ixodidae) and tick-borne pathogens affecting wild animals at these locations. In this study, 1197 adult ixodid ticks infesting wild boars were collected from 10 sampling sites during 2019. Ticks were identified to species based on morphology, and the identification was confirmed based on mitochondrial 16S, ITS1 and ITS2 rRNA sequences. Eight tick species belonging to 2 genera were identified, including H. longicornis (n = 373, 31.1%), H. flava (n = 265, 22.1%), D. auratus (n = 153, 12.8%), H. hystricis (n = 119, 9.9%), D. silvarum (n = 116, 9.7%), H. bispinosa (n = 114, 9.5%), D. atrosignatus (n = 33, 2.8%), and D. taiwanensis (n = 24, 2.0%). DNA sequences of Rickettsia spp. (spotted fever group) and Babesia spp. were detected in these ticks. Phylogenetic analyses revealed the possible existence of Candidatus Rickettsia laoensis and Rickettsia raoultii. This study illustrates the potential threat to wild animals and humans from tick-borne pathogens.

Molecular detection of pathogens from ectoparasites recovered from peri-domestic animals, and the first description of a Candidatus Midichloria sp. from Haemaphysalis wellingtoni from rural communities in Malaysia

Rural communities in Malaysia have been shown to be exposed to Coxiella, Borrelia and rickettsial infections in previous seroprevalence studies. Further research is necessary to identify the actual causative agents and the potential vectors of these infections. The arthropods parasitizing peri-domestic animals in these communities may serve as the vector in transmitting arthropod-borne and zoonotic agents to the humans. Molecular screening of bacterial and zoonotic pathogens from ticks and fleas collected from dogs, cats and chickens from six rural communities in Malaysia was undertaken. These communities were made up of mainly the indigenous people of Malaysia, known as the Orang Asli, as well as settlers in oil palm plantations. The presence of Coxiella burnetii, Borrelia, and rickettsial agents, including Rickettsia and Anaplasma, was investigated by performing polymerase chain reaction (PCR) and DNA sequencing. Candidatus Rickettsia senegalensis was detected in one out of eight pools of Ctenocephalides felis fleas. A relapsing fever group Borrelia sp. was identified from one of seven Haemaphysalis hystricis ticks tested. The results from the PCR screening for Anaplasma unexpectedly revealed the presence of Candidatus Midichloria sp., a potential tick endosymbiont, in two out of fourteen Haemaphysalis wellingtoni ticks tested. C. burnetii was not detected in any of the samples tested. The findings here provide evidence for the presence of potentially novel strains of rickettsial and borrelial agents in which their impact on public health risks among the rural communities in Malaysia merit further investigation. The detection of a potential endosymbiont of ticks also suggest that the presence of tick endosymbionts in the region is not fully explored.

Emergence of the zoonotic tick Dermacentor (Indocentor) auratus Supino, 1897 (Acari: Ixodidae) in Singapore

Though ticks pose a significant public health risk, until recently, little research had focused on the diversity of ticks and tick-borne diseases in Singapore. To date, only fourteen tick species in five genera have been recorded there. For the first time, Dermacentor auratus is recorded from Singapore from a range of hosts, including humans. DNA sequences are provided at 2 loci, for D. auratus, the cytochrome c oxidase I (COI) for DNA barcoding and the 16S large subunit ribosomal RNA (16S lsu rRNA). The health risk posed by D. auratus in Singapore is discussed.

Ticks and tick-borne pathogens in animals and humans in the island nations of Southeast Asia: A review

Ticks are blood-feeding ectoparasites and major vectors of pathogens that cause infectious diseases in humans and animals worldwide including mammals, birds and reptiles. Despite the growing scientific effort in the 20th century, there is still limited information on ticks and tick-borne pathogens in Southeast Asia, especially concerning medical, veterinary, socioeconomic and agricultural aspects in the island nations. This review provides an overview of the current state of knowledge of ticks and their pathogens in the island nations of Southeast Asia and peninsular Malaysia. We aim to stimulate further research studies on ticks and tick-borne pathogens of human and veterinary importance in this geographical region.

An overview of rickettsiae in Southeast Asia: Vector-animal-human interface

Rickettsioses are emerging, and re-emerging diseases caused by obligate intracellular arthropod-borne bacteria that infect humans and animals worldwide. Various rickettsiae such as Orientia, Rickettsia, Anaplasma and Ehrlichia have been circulated in companion, domesticated and wild animals through bites of infected ticks, fleas, lice or mites. This review summarizes the infections of rickettsiae, including the newly discovered regional species Rickettsia thailandii, Candidatus Rickettsia sepangensis, Candidatus Rickettsia johorensis, Candidatus Rickettsia laoensis, Candidatus Rickettsia mahosotii, Candidatus Rickettsia khammouanensis, Candidatus Anaplasma pangolinii, and other novel genotypes in vectors, humans and animals in Southeast Asia. Issues on some unidentified rickettsiae that elicit immune responses and production of antibodies that are cross-reactive with the antigens used are discussed. Knowledge gaps which required attention are also identified in this review.

Distribution and Ecological Drivers of Spotted Fever Group Rickettsia in Asia

Spotted fever group and related rickettsia (SFGR) are a neglected group of pathogens that belong to the genus Rickettsia. SFGR are zoonotic and are transmitted by arthropod vectors, primarily ticks, fleas and mites to accidental hosts. These emerging and re-emerging infections are widely distributed throughout the world. Land-use change and increasing human-wildlife conflict compound the risk of SFGR infection to local people in endemic areas and travelers to these regions. In this article, we discuss the rickettsial organisms causing spotted fever and related diseases, their arthropod vectors in Asia and the impact of land-use change on their spread.

Diagnosis of spotted fever group Rickettsia infections: the Asian perspective

Spotted fever group rickettsiae (SFG) are a neglected group of bacteria, belonging to the genus Rickettsia, that represent a large number of new and emerging infectious diseases with a worldwide distribution. The diseases are zoonotic and are transmitted by arthropod vectors, mainly ticks, fleas and mites, to hosts such as wild animals. Domesticated animals and humans are accidental hosts. In Asia, local people in endemic areas as well as travellers to these regions are at high risk of infection. In this review we compare SFG molecular and serological diagnostic methods and discuss their limitations. While there is a large range of molecular diagnostics and serological assays, both approaches have limitations and a positive result is dependent on the timing of sample collection. There is an increasing need for less expensive and easy-to-use diagnostic tests. However, despite many tests being available, their lack of suitability for use in resource-limited regions is of concern, as many require technical expertise, expensive equipment and reagents. In addition, many existing diagnostic tests still require rigorous validation in the regions and populations where these tests may be used, in particular to establish coherent and worthwhile cut-offs. It is likely that the best strategy is to use a real-time quantitative polymerase chain reaction (qPCR) and immunofluorescence assay in tandem. If the specimen is collected early enough in the infection there will be no antibodies but there will be a greater chance of a PCR positive result. Conversely, when there are detectable antibodies it is less likely that there will be a positive PCR result. It is therefore extremely important that a complete medical history is provided especially the number of days of fever prior to sample collection. More effort is required to develop and validate SFG diagnostics and those of other rickettsial infections.

Diversity of Rickettsiae in Feeding and Questing Ticks Collected From a Malaysian Forest Reserve Area

High seropositivity to Rickettsia conorii and Rickettsia felis has been reported in Malaysian indigenous community living in settlements adjacent to forest areas. The current study was conducted to determine the type and distribution of rickettsiae in feeding and questing ticks that were collected from a forest reserve area at Kuala Lompat in Pahang, Malaysia. Using PCR assays targeting citrate synthase (gltA), outer membrane protein A (ompA) and B (ompB) genes, rickettsiae were detected from approximately one-third of 98 ticks (mainly Dermacentor and Haemaphysalis spp.) collected from the forest reserve. BLAST analysis reveals the predominance of Rickettsia sp. RF2125 in both feeding and questing ticks and Rickettsia sp. TCM1 in the questing ticks. Sequences exhibiting close genetic relationship with Rickettsia raoultii, Rickettsia tamurae, Rickettsia heilongjiangensis, and Rickettsia asiatica were also detected from the ticks. This study highlights the diversity of rickettsial species and potential tick vectors which may contribute to the high seropositivity observed among the local communities.

Seroprevalence of Tick-Borne Anaplasma phagocytophilum Infection in Healthy Adult Population and Patients with Acute Undifferentiated Fever from the Yunnan Province of China

Anaplasma phagocytophilum-the causative agent of human granulocytic anaplasmosis (HGA)-is a tick-borne pathogen transmitted by Ixodid ticks infecting wild and domestic mammals as well as humans. Despite the availability of evidence regarding this emerging infection among vectors, host animals, and individuals in China, there is limited knowledge on the prevalence and distribution of A. phagocytophilum in the Yunnan Province. The aim of this study was to assess the seroprevalence of A. phagocytophilum in healthy adults and patients with acute undifferentiated fever from four regions in the Yunnan Province. The enzyme-linked immunosorbent assay and indirect immunofluorescence assay were used to detect immunoglobulin (Ig) G and IgM antibodies against A. phagocytophilum in sera obtained from 1185 healthy blood donors and 245 patients with acute undifferentiated fever, respectively. Demographic variables were assessed as potential risk factors using the chi-squared test. The rates of seropositivity rates were 7.59% and 4.49% in healthy donors and fever patients, respectively. Analysis of risk factors such as gender, age groups, and place of residence showed statistically significant differences. Infections with A. phagocytophilum occur widely among individuals residing in southwestern China. Our results indicate that there is serological evidence of HGA in this population and presence of acute A. phagocytophilum infections in patients with undifferentiated fever in the Yunnan Province.

The Genus Dermacentor (Acari: Ixodidae) in Laos: A Review and Update of Species Records

Two species of the ixodid tick genus Dermacentor Koch, 1844 (Acari: Ixodidae) have previously been documented from Laos: D. auratus Supino, 1897 and D. steini (Schulze, 1933). Between 2012 and 2017, we recorded four additional Dermacentor species from this country: D. bellulus (Schulze, 1935); D. compactus Neumann, 1901; D. filippovae Apanaskevich & Apanaskevich, 2015; and D. tamokensisApanaskevich & Apanaskevich, 2016. In addition, seven specimens in the tick collection at the Institut Pasteur du Laos may represent new species and are currently under taxonomic investigation.

First Report of Ixodes nipponensis Infection in Goats in China

Ticks are obligate blood-sucking ectoparasites that infect a wide range of animals and humans, causing a variety of both human and animal diseases around the world. Ixodes nipponensis is the most commonly reported tick in Korea and Japan, but it is very rare in China. In this study, six I. nipponensis samples were collected from three black goats in Hunan province, China. Ticks identified morphologically as I. nipponensis were then examined by PCR with two different molecular markers: mitochondrial cox1 and the second internal transcribed spacer of ribosomal DNA genes. Sequence comparison and phylogenetic analysis of the cox1 sequences confirmed that all of the examined hard Ixodes ticks represented I. nipponensis. This finding indicates a potential risk of zoonotic I. nipponensis infection in humans and animals in China. To our knowledge, this is the first report documenting the occurrence of I. nipponensis infection in goats in China.

Tick-transmitted human infections in Asia

Vector-borne pathogens of human significance cause a predicted 17% of infectious diseases worldwide, of which, ~23% are tick transmitted1. Although second to mosquitoes in terms of impact, ticks are thought to carry a greater diversity of pathogens than other arthropod vectors2. Asia is a key region for tick-borne pathogens, with tick species typically restricted to latitudes below 60–55°N3 where the climate is warmer and wetter – from the steppe regions of Russia to the tropical rainforests of South East Asia.