Co-circulation of multiple species of Rickettsiales bacteria in one single species of hard ticks in Shenyang, China

Molecular detection of Rickettsiales and a potential novel Ehrlichia species closely related to Ehrlichia chaffeensis in ticks (Acari: Ixodidae) from Shaanxi Province, China, in 2022 to 2023

Important tick-borne diseases include spotted fever group Rickettsia (SFGR), Anaplasma, and Ehrlichia, which cause harm to animal and human health. Ixodidae are the primary vectors of these pathogens. We aimed to analyze the prevalence and genetic diversity of SFGR, Anaplasma, and Ehrlichia species in the Ixodidae in Shaanxi Province, China. Herein, 1,113 adult Ixodidae ticks were collected from domestic cattle and goats, and detected using nested PCR. A total of four Ixodidae species were collected and Ca. R. jingxinensis (20.58%, 229/1113), A. bovis (3.05%, 34/1113), A. capra (3.32%, 37/1113), A. marginale (0.18%, 2/1113), E. sp. Yonaguni138 (0.18%, 2/1113), and a potent novel Ehrlichia species named E. sp. Baoji96 (0.09%, 1/1113) were detected. A. marginale was detected for the first time in Rhipicephalus microplus. E. sp. Baoji96 was closely related to E. chaffeensis and was first identified in Haemaphysalis longicornis. In addition, co-infection with two Rickettsiales pathogens within an individual tick was detected in 10 (1.54%) ticks. This study provides a reference for the formulation of biological control strategies for ticks and tick-borne diseases in Shaanxi Province, and could lead to an improved control effect.

Emergence of ehrlichiosis by a new tick-borne Ehrlichia species in China

OBJECTIVES

From March to June 2021, the reported number of clinically diagnosed endemic typhus in Anhui and Hubei provinces of China nearly increased four-fold compared with the monthly average numbers in last 5 years. An etiological and epidemiological investigation was initiated.

METHODS

The clinical specimens from the reported patients and the potential vector ticks were collected for molecular and serological detection, as well as cell culturing assay to identify the potential pathogen.

RESULTS

Polymerase chain reaction and sequence analysis of rrs and groEL showed that the pathogen from these patients was Ehrlichia sp., isolated from Haemaphysalis longicornis attached to these patients. The phylogenetic analysis based on 39 Ehrlichia genomes suggested that it should be taxonomically classified as a novel species, tentatively named "Candidatus Ehrlichia erythraense". A total of 19 of 106 cases were confirmed as Candidatus Ehrlichia erythraense infections by polymerase chain reaction, sequencing, and/or serological tests. The most frequent symptoms were fever (100%), rashes (100%), asthenia (100%), anorexia (100%), and myalgia (79%).

CONCLUSION

The occurrence of the disease presenting with fever and rashes in Anhui and Hubei provinces was caused by a novel species of the genus Ehrlichia; physicians need to be aware of this newly-discovered pathogen to ensure appropriate testing, treatment, and regional surveillance.

Detection and Genotypic Analysis of Anaplasma bovis and A. phagocytophilum in Horse Blood and Lung Tissue

A clinical case of Anaplasma bovis was reported for the first time in our previous study (2019) in a horse, a nondefinitive host. Although A. bovis is a ruminant and not a zoonotic pathogen, it is responsible for persistent infections in horses. In this follow-up study, the prevalence of Anaplasma spp., including A. bovis, was assessed in horse blood and lung tissue samples to fully understand Anaplasma spp. pathogen distribution and the potential risk factors of infection. Among 1696 samples, including 1433 blood samples from farms nationwide and 263 lung tissue samples from horse abattoirs on Jeju Island, a total of 29 samples (1.7%) tested positive for A. bovis and 31 (1.8%) samples tested positive for A. phagocytophilum, as determined by 16S rRNA nucleotide sequencing and restriction fragment length polymorphism. This study is the first to detect A. bovis infection in horse lung tissue samples. Further studies are needed to clarify the comparison of sample types within cohorts. Although the clinical significance of Anaplasma infection was not evaluated in this study, our results emphasize the need to clarify the host tropism and genetic divergence of Anaplasma to enable the development of effective prevention and control measures through broad epidemiological studies.

Detection and phylogenetic analysis of tick-borne bacterial and protozoan pathogens in a forest province of eastern China

Ticks, as obligate blood-sucking ectoparasites, feed on a broad range of vertebrates and transmit a great diversity of pathogenic microorganisms. Some tick-borne pathogens (TBPs) are endemic in China, whereas epidemiological studies are limited in Jiangxi, a forest province located in eastern China. Here, we have determined the positivity rates of TBPs in humans, rodents, dogs, goats and ticks, and performed the molecular characterization of TBPs in Jiangxi province. We found a high positivity rate of TBPs in the collected samples, demonstrating 23 (12.92%) samples positive for more than one TBPs. Of those, 11 (6.18%) samples were positive for Rickettsia spp., six (3.37%) Ehrlichia spp./Anaplasma spp., one (0.56%) Bartonella spp., two (1.12%) Borrelia spp., and five (2.81%) Babesia spp. The positivity rates of TBPs varied among ticks, animals, and humans as follow: goats (14/37, 37.84%), ticks (8/35, 22.86%), and dogs (1/11, 9.09%). Humans and rodents were negative for TBP presence. Phylogenetic analyses of these TBP sequences revealed the presence of Rickettsia japonica, Ehrlichia minasensis, and an unclassified Babesia spp. in goats, and Anaplasma phagocytophilum, Borrelia valaisiana, and an unclassified Bartonella spp. in ticks. Furthermore, R. japonica infection was exclusively found in goats with the positivity rate of 29.73%. Our study is the first report of R. japonica in goats around the world. These findings suggest high TBP positivity rates among goats, ticks, and dogs, and diverse TBPs in goats and ticks in the studied sites. Therefore, our results underscore the urgent need to assess TBP-tick-vertebrate-environment interactions and the risk of tick borne disease exposure in humans in the future.

First report on molecular characteristics and risk factor analysis of Ehrlichia canis in dogs in Khon Kaen, Thailand

Background and Aim:

Ehrlichia canis is a well-known cause of both anemia and thrombocytopenia in dogs. There are insufficient epidemiological data on this blood parasite in Thailand and the association of infections with hematological abnormalities. This study aimed to analyze the molecular characteristics and to identify E. canis as well as the risk factors associated with E. canis infection in dogs in Khon Kaen, Thailand.

Materials and Methods:

Blood samples from 126 dogs that visited animal clinics were subjected to molecular detection using nested polymerase chain reaction for E. canis16S rRNA gene. The risk factors and hematological profiles associated with the infection were analyzed using the logistic regression test in program SPSS version 19.

Results:

Forty-one dogs were infected, indicating a 32.5% molecular infection rate of E. canis. The factors significantly associated with E. canis infection include animal housing status, low packed cell volume, low red blood cell count, and low platelets (p<0.05). Ten positive samples were amplified, sequenced, and phylogenetically analyzed. Sequence and phylogenetic analysis confirmed the current ten samples as E. canis compared with reference sequences in GenBank, using the BLAST program hosted by NCBI, which showed 99.74-100% similarity.

Conclusion:

This study provided the first data of infection rate of E. canis using nested PCR and molecular characteristics of E. canis in randomly selected domestic dogs in Khon Kaen, Thailand.

Identification of Tick-Borne Pathogens and Genotyping of Coxiella burnetii in Rhipicephalus microplus in Yunnan Province, China

Rhipicephalus microplus, a vector that can transmit many pathogens to humans and domestic animals, is widely distributed in Yunnan province, China. However, few reports on the prevalence of tick-borne pathogens (TBPs) in Rh. microplus in Yunnan are available. The aim of this study was to detect TBPs in Rh. microplus in Yunnan and to analyze the phylogenetic characterization of TBPs detected in these ticks. The adult Rh. microplus (n = 516) feeding on cattle were collected. The pooled DNA samples of these ticks were evaluated using metagenomic next-generation sequencing (mNGS) and then TBPs in individual ticks were identified using genus- or group-specific nested polymerase chain reaction (PCR) combined with DNA sequencing assay. As a result, Candidatus Rickettsia jingxinensis (24.61%, 127/516), Anaplasma marginale (13.18%, 68/516), Coxiella burnetii (3.10%, 16/516), and Coxiella-like endosymbiont (CLE) (8.33%, 43/516) were detected. The dual coinfection with Ca. R. jingxinensis and A. marginale and the triple coinfection with Ca. R. jingxinensis, A. marginale, and CLE were most frequent and detected in 3.68% (19/516) and 3.10% (16/516) of these ticks, respectively. The results provide insight into the diversity of TBPs and their coinfections in Rh. microplus in Yunnan province of China, reporting for the first time that C. burnetii had been found in Rh. microplus in China. Multilocus variable number tandem repeat analysis with 6 loci (MLVA-6) discriminated the C. burnetii detected in Rh. microplus in Yunnan into MLVA genotype 1, which is closely related to previously described genotypes found primarily in tick and human samples from different regions of the globe, indicating a potential public health threat posed by C. burnetii in Rh. microplus in Yunnan.

Molecular detection and phylogenetic analyses of Anaplasma spp. in Haemaphysalis longicornis from goats in four provinces of China

Anaplasma species, which are distributed worldwide, are gram-negative obligate intracellular tick-borne bacteria that pose a threat to human and animal health. Haemaphysalis longicornis ticks play a vital role as vectors in the transmission of Anaplasma pathogens. However, the Anaplasma species carried by H. longicornis in China are yet to be characterized. In this study, 1074 H. longicornis specimens were collected from goats in four provinces of China from 2018 to 2019 and divided into 371 sample pools. All tick sample pools were examined for the presence of Anaplasma species via nested PCR amplification of 16S ribosomal RNA, major surface protein 4 (msp4), or citric acid synthase (gltA) genes, which were sequenced to determine the molecular and phylogenetic characteristics of the isolates. The overall Anaplasma spp-positive rate of H. longicornis was determined to be 26.68% (99/371). The percentage prevalence of A. phagocytophilum-like1, A. bovis, A. ovis, A. marginale, and A. capra were 1.08% (4/371), 13.21% (49/371), 13.21% (49/371), 1.35% (5/371), and 10.24% (38/371), respectively, and the co-infection rate of two or more types of Anaplasma was 6.47% (24/371). Phylogenetic analyses led to the classification of A. phagocytophilum into an A. phagocytophilum-like1 (Anaplasma sp. Japan) group. Anaplasma bovis sequences obtained in this study were 99.8–100% identical to those of an earlier strain isolated from a Chinese tick (GenBank accession no. KP314251). Anaplasma ovis sequences showed 99.3–99.6% identity to an A. ovis human strain identified from a Cypriot patient (GenBank accession no. FJ460443). Only one msp4 sequence of A. marginale was detected and was grouped with those of other A. marginale isolates, and these A. capra isolates obtained in this present study may be zoonotic. The detection and characterization of four Anaplasma species in H. longicornis in this study have added to the current knowledge of the parasite and provided data on multiple Anaplasma species with veterinary and medical significance from four provinces of China.

iSeq 100 for metagenomic pathogen screening in ticks

BACKGROUND

Ticks are blood-sucking ectoparasites that play a pivotal role in the transmission of various pathogens to humans and animals. In Korea, Haemaphysalis longicornis is the predominant tick species and is recognized as the vector of pathogens causing various diseases such as babesiosis, borreliosis, rickettsiosis, and severe fever with thrombocytopenia syndrome.

METHODS

In this study, the targeted high-throughput sequencing of the 16S rRNA V4 region was performed using the state-of-the-art sequencing instrument, iSeq 100, to screen bacterial pathogens in H. longicornis, and the findings were compared with those using conventional PCR with specific primers. Microbiome analyses were performed with EzBioCloud, a commercially available ChunLab bioinformatics cloud platform. ANOVA-Like Differential Expression tool (ALDEx2) was used for differential abundance analysis.

RESULTS

Rickettsia spp. were detected in 16 out of 37 samples using iSeq 100, and this was confirmed using a PCR assay. In the phylogenetic analysis using gltA and ompA sequences of the detected Rickettsia, the highest sequence similarity was found with 'Candidatus Rickettsia jingxinensis' isolate Xian-Hl-79, 'Ca. R. jingxinensis' isolate F18, and 'Ca. R. longicornii' isolate ROK-HL727. In the microbiome study, Coxiella AB001519, a known tick symbiont, was detected in all 37 tick samples. Actinomycetospora chiangmaiensis was more abundant in Rickettsia-positive samples than in Rickettsia-negative samples.

CONCLUSIONS

In this study, iSeq 100 was used to investigate the microbiome of H. longicornis, and the potentially pathogenic Rickettsia strain was detected in 16 out of 37 ticks. We believe that this approach will aid in large-scale pathogen screening of arthropods to be used in vector-borne disease control programs.

Detection of Novel Spotted Fever Group Rickettsiae (Rickettsiales: Rickettsiaceae) in Ticks (Acari: Ixodidae) in Southwestern China

Spotted fever group rickettsiae, mainly maintained and transmitted by ticks, are important etiological agents of (re)emerging zoonotic diseases worldwide. It is of great significance to investigate spotted fever group rickettsiae in ticks in different areas for the prevention and control of rickettsioses. In this study, a total of 305 ticks were collected from wild and domestic animals in Chongqing, Guizhou, Yunnan, and Guangxi provinces of southwestern China during 2017-2019 and examined for the presence of spotted fever group rickettsiae by PCR with primers targeting the partial gltA, ompA, rrs, and htrA genes. Results showed that two spotted fever group rickettsiae species, including the pathogenic Candidatus Rickettsia jingxinensis (Rickettsiales: Rickettsiaceae) and a potential novel species Rickettsia sp. sw (Rickettsiales: Rickettsiaceae), were identified. The Ca. R. jingxinensis sequences were recovered from Rhipicephalus microplus (Ixodida: Ixodidae) and Haemaphysalis longicornis (Ixodida: Ixodidae) ticks and phylogenetically clustered with previous Ca. R. jingxinensis, Ca. R. longicornii (Rickettsiales: Rickettsiaceae), and Rickettsia sp. XY118 (Rickettsiales: Rickettsiaceae) strains. Rickettsia sp. sw was detected in Amblyomma geoemydae (Ixodida: Ixodidae) and Rh. microplus. Interestingly, as far as we know, this was the first report of Rickettsia (Rickettsiales: Rickettsiaceae) in A. geoemydae. Phylogenetic analyses indicated that this potential novel species was closely related to R. aeschlimannii (Rickettsiales: Rickettsiaceae) with gltA and ompA genes and grouped in a cluster composed of R. montanensis (Rickettsiales: Rickettsiaceae), R. raoultii (Rickettsiales: Rickettsiaceae), R. aeschlimannii, R. massiliae (Rickettsiales: Rickettsiaceae), and R. rhipicephali (Rickettsiales: Rickettsiaceae) with htrA, while formed a separate clade with rrs. The pathogenicity of Rickettsia sp. sw should be further confirmed. These results expand the knowledge of the geographical distribution and vector distribution of spotted fever group rickettsiae in China and are useful for assessing the potential public health risk.

Incompetence of the Asian Longhorned Tick (Acari: Ixodidae) in Transmitting the Agent of Human Granulocytic Anaplasmosis in the United States

The Asian longhorned tick, Haemaphysalis longicornis Neumann (Acari: Ixodidae), was recently introduced into the United States and is now established in at least 15 states. Considering its ability for parthenogenetic propagation and propensity for creating high-density populations, there is concern that this tick may become involved in transmission cycles of endemic tick-borne human pathogens. Human granulocytic anaplasmosis (HGA) caused by Anaplasma phagocytophilum is one of the more common tick-borne diseases in the United States, especially in the northeastern and midwestern states. There is considerable geographical overlap between HGA cases and the currently known distribution of H. longicornis, which creates a potential for this tick to encounter A. phagocytophilum while feeding on naturally infected vertebrate hosts. Therefore, we evaluated the ability of H. longicornis to acquire and transmit the agent of HGA under laboratory conditions and compared it to the vector competence of I. scapularis. Haemaphysalis longicornis nymphs acquired the pathogen with the bloodmeal while feeding on infected domestic goats, but transstadial transmission was inefficient and PCR-positive adult ticks were unable to transmit the pathogen to naïve goats. Results of this study indicate that the Asian longhorned tick is not likely to play a significant role in the epidemiology of HGA in the United States.

Expansion of Tick-Borne Rickettsioses in the World

Tick-borne rickettsioses are caused by obligate intracellular bacteria belonging to the spotted fever group of the genus Rickettsia. These infections are among the oldest known diseases transmitted by vectors. In the last three decades there has been a rapid increase in the recognition of this disease complex. This unusual expansion of information was mainly caused by the development of molecular diagnostic techniques that have facilitated the identification of new and previously recognized rickettsiae. A lot of currently known bacteria of the genus Rickettsia have been considered nonpathogenic for years, and moreover, many new species have been identified with unknown pathogenicity. The genus Rickettsia is distributed all over the world. Many Rickettsia species are present on several continents. The geographical distribution of rickettsiae is related to their vectors. New cases of rickettsioses and new locations, where the presence of these bacteria is recognized, are still being identified. The variety and rapid evolution of the distribution and density of ticks and diseases which they transmit shows us the scale of the problem. This review article presents a comparison of the current understanding of the geographic distribution of pathogenic Rickettsia species to that of the beginning of the century.

Distribution and molecular characterization of rickettsiae in ticks in Harbin area of Northeastern China

Tick-borne rickettsioses are world-spreading infectious zoonoses. Ticks serve as reservoirs and vectors for Rickettsia and play a key role in transmission of rickettsioses. Most of the Chinese rickettsiosis patients are reported from Northeastern China but the distribution of tick and tick-borne Rickettsia species in Northeastern China remain poorly studied. In this study, a total of 1,286 ticks were captured from the seven counties of Harbin, an area in Northeastern China, and the tick-borne Rickettsia species were identified by PCR and sequencing of rrs, gltA, groEL, ompA and 17-kDa antigen-encoding genes. Of the 5 identified tick species, Haemaphysalis longicornis and Ixodes persulcatus were the predominant tick species in the livestock and vegetation, respectively. Rickettsia raoultii and “Candidatus Rickettsia tarasevichiae” were the two detectable Rickettsia species in the ticks with a 28.8% positive rate but no rickettsiae were found in ticks of Haemaphysalis concinna. R. raoultii detected in 37.6% of the Dermacentor nuttalli, Dermacentor silvarum and H. longicornis ticks while “Ca. R. tarasevichiae” was only present in 22.8% of the I. persulcatus ticks. In particular, the positive rate of both R. raoultii and “Ca. R. tarasevichiae” in ticks from the livestock (40.7%) was significantly higher than that from the vegetation (19.5%). The results indicate that the tick and tick-borne Rickettsia species are diverse in different regions of Harbin due to geographic difference and the ticks from livestock may play a more important role in transmission of rickettsioses to human.

Rickettsiosis is a tick-borne infectious disease of global importance. The disease has been prevailing in Northeastern China but the distribution of tick and tick-borne Rickettsia species from different areas of Northeastern China remain poorly studied. We collected a total of 1,286 ticks in the seven counties with different geographic environments of Harbin, an area of Northeastern China, and all the ticks were classified as Dermacentor nuttalli, Dermacentor silvarum, Haemaphysalis concinna, Haemaphysalis longicornis or Ixodes persulcatus. A total of 28.8% of the ticks tested positive for either Rickettsia raoultii or “Candidatus Rickettsia tarasevichiae”, in which 37.6% of the D. nuttalli, D. silvarum and H. longicornis ticks were positive for R. raoultii while 22.8% of the I. persulcatus ticks were positive for “Ca. R. tarasevichiae”. The positive rate of both R. raoultii and “Ca. R. tarasevichiae” in ticks from the livestock (40.7%) was significantly higher than that from the vegetation (19.5%). All the data indicate that ticks in the Harbin area have a high infection rate with Rickettsia species and domestic animals may have a tick-livestock rickettsial circulation that may play an important role in transmission of rickettsioses.

Molecular detection of tick-borne pathogens harbored by ticks collected from livestock in the Xinjiang Uygur Autonomous Region, China

Ticks carry and transmit a wide range of pathogens (bacteria, viruses, and protozoa) that are of importance to humans and animals globally. However, information about the tick-borne pathogens harbored by ticks in the Xinjiang Uygur Autonomous Region (XUAR), northwestern China, is scarce. This study investigated the occurrence of tick species of domestic animals and tick-borne pathogens by using morphological molecular identification and sequence analysis in Turpan, Qitai, Altay, Hejing, Nileke, and Zhaosu counties (XUAR). A total of 5822 adult ticks (females and males) from 12 tick species were identified from 5 animal species (cattle, goats, sheep, camels, and horses) in 6 counties in the XUAR. Collected tick species included Dermacentor marginatus (24.7 %), Dermacentor nuttalli (20.8 %), Hyalomma anatolicum (13.7 %), Dermacentor niveus (13.1 %), Haemaphysalis punctata (10.7 %), Dermacentor silvarum (7.1 %), Dermacentor pavlovskyi (3.9 %), Hyalomma asiaticum (2.2 %), Rhipicephalus pumilio (1.9 %), Rhipicephalus sanguineus sensu lato (0.7 %), Rhipicephalus turanicus (0.6 %), and Hyalomma asiaticum kozlovi (0.6 %). Furthermore, 750 partially engorged adult ticks (females and males), including H. anatolicum (250), D. nuttalli (250), and D. marginatus (250), were individually separated according to species and sampling site, used for DNA extraction, and then screened for tick-borne pathogens. The most common pathogen was Rickettsia raoultii (36.80 %), followed by Brucella sp. (26.2 %), Anaplasma ovis (22.4 %), Babesia caballi (14.8 %), Theileria equi (8.7 %), and Theileria ovis (8.5 %). The sequencing of 6 genes showed a 96-100 % nucleotide identity between the sequences in this study and those deposited in GenBank. This study provides a scientific reference for the prevention and control of tick-borne diseases in the XUAR.

Extensive genetic diversity of Anaplasma bovis in ruminants in Xi'an, China

Anaplasma bovis is an organism significant to cattle and buffalo since it is one of the causative agents of bovine anaplasmosis. Previous studies have shown the worldwide distribution of A. bovis. However, most of these studies about its genetic diversity only focused on the rrs gene. In this study, DNA of A. bovis was detected in blood samples of cattle and goats in Xi'an city, China by nested-PCR. Near full-length rrs, groEL, and gltA genes were amplified successfully from the positive samples. Genetic analysis showed that specific genetic marker (an insertion and a deletion) was found in the rrs sequences in some strains, as well as clone 88 from monkeys in previous study. Phylogenetic analysis based on the rrs, groEL, and gltA genes revealed that A. bovis circulating in Xi'an exhibited great genetic diversity. Our results also indicated that variants outside China presented geographic clustering, and all A. bovis isolates based on the groEL or gltA gene also showed a host origin clustering. Also of note was that the phylogenetic analyses of the groEL and gltA genes suggested that both frequent dispersals over long distances in recent years and local adaptation over long evolutionary timescales played important roles in the distribution and evolution of A. bovis in China. Finally, a potential recombination event in the genome of Zhouzhi-cattle-10 based on inconsistent positions in the groEL and gltA trees was also observed. These results also reinforce the need for assessing the pathogenicity to humans of A. bovis variants with specific marker in the rrs gene.

Molecular evidence of the spotted fever group Rickettsiae in ticks from Yunnan Province, Southwest China

Ixodid ticks transmit many obligate intracellular Rickettsial species. Several previous studies have identified Rickettsia species in the northeastern and southern part of China, but few reports on the prevalence of infection of spotted fever group Rickettsiae (SFGR) in ticks in southwest China are available. Here, we investigated SFGR in 394 adult ticks of five species including Dermacentor nuttalli, Dermacentor silvarum, Haemaphysalis longicornis, Ixodes sinensis and Ixodes persulcatus, collected in the border region between China and Burma in Yunnan Province. PCR was used to detect the presence of the citrate synthase (gltA) gene of Rickettsia species. SFGR was found in 12.1% (15/124) of I. persulcatus ticks, which was significantly higher than the 7.2% (7/97) positive D. nuttalli, 5.4% (3/56) D. silvarum, 5.6% (4/72) H. longicornis and 4.4 (2/45) I. sinensis. A portion of the gltA and ompA gene data subjected to phylogenetic analysis revealed that the detected SFGR clustered into two species, Rickettsia raoultii and the new Rickettsia species Candidatus Rickettsia jingxinensis. Detection of both Rickettsia spp. in this region indicates a potential public health threat posed by SFGR infection in Yunnan Province.

Insight into diversity of bacteria belonging to the order Rickettsiales in 9 arthropods species collected in Serbia

Rickettsiales bacteria in arthropods play a significant role in both public health and arthropod ecology. However, the extensive genetic diversity of Rickettsiales endosymbionts of arthropods is still to be discovered. In 2016, 515 arthropods belonging to 9 species of four classes (Insecta, Chilopoda, Diplopoda and Arachnida) were collected in Serbia. The presence and genetic diversity of Rickettsiales bacteria were evaluated by characterizing the 16S rRNA (rrs), citrate synthase (gltA) and heat shock protein (groEL) genes. The presence of various Rickettsiales bacteria was identified in the majority of tested arthropod species. The results revealed co-circulation of five recognized Rickettsiales species including Rickettsia, Ehrlichia and Wolbachia, as well as four tentative novel species, including one tentative novel genus named Neowolbachia. These results suggest the remarkable genetic diversity of Rickettsiales bacteria in certain arthropod species in this region. Furthermore, the high prevalence of spotted fever group Rickettsia in Ixodes ricinus ticks highlights the potential public health risk of human Rickettsia infection.

Isolation and Identification of Rickettsia raoultii in Human Cases: A Surveillance Study in 3 Medical Centers in China

Background

Rickettsia raoultii is frequently detected in multiple tick species, whereas human infection remains scarcely studied.

Methods

A surveillance study was performed at 3 sentinel hospitals in China, to recruit participants with suspected tick exposure. Rickettsia raoultii infection was identified through polymerase chain reaction, followed by sequencing, and confirmed serologically. Isolation by cell culture was performed and the isolates were genome sequenced.

Results

Twenty-six subjects were determined to have R. raoultii infection, including 7 with asymptomatic infection, 15 with mild to moderate illness, and 4 with severe illness. Common nonspecific manifestations in the 19 patients with mild to moderate or severe illness included fever (100%), malaise (95%), myalgia (58%), lymphadenopathy (53%), and nausea (42%). Only 5% of them had rash, and 16% had eschar. Scalp eschar and neck lymphadenopathy after a tick bite syndrome was only seen in 2 patients. Of the 4 patients with severe complications, 3 developed pulmonary edema, and 1 developed clouding of consciousness and lethargy. Frequent abnormalities of laboratory testing included leukopenia, thrombocytopenia, lymphopenia, neutropenia, hypoproteinemia, and elevated levels of total bilirubin, hepatic aminotransferases, lactate dehydrogenase, and creatine kinase. All the 19 patients recovered without sequelae after receiving doxycycline treatment. Two R. raoultii strains were isolated, and a significantly less degraded genome was observed than other more virulent Rickettsia strains, indicating a low pathogenicity of the current strain.

Conclusions

Human infection with R. raoultii has a wide clinical spectrum that ranged from subclinical infection to severe complications. Physicians need to be aware of the high potential and clinical complexity of R. raoultii infection, to ensure appropriate testing and treatment in endemic regions.

GroEL gene typing and genetic diversity of Anaplasma bovis in ticks in Shaanxi, China

Anaplasma bovis, causative agent of bovine anaplasmosis, is usually identified by nested-PCR amplifying the rrs gene. However, it is difficult to determine the genetic relationship among different variants within A. bovis using this gene because of high conservation. In this study, two tick species, identified as Rhipicephalus microplus and Haemaphysalis longicornis based on morphological and molecular methods by analyzing COI gene, were collected from cattle, goat or sheep. Subsequently, A. bovis was initially detected by PCR amplifying the rrs gene in ticks in Shaanxi Province, China. The sequencing and Blast results showed that some false positive samples were found when only based on the amplification of partial rrs gene, presenting these sequences resembled those of other Alphaproteobacteria rather than A. bovis. Although major surface proteins genes were proposed and used successfully to identify members within Anaplasmataceae, these genes were unavailable for A. bovis. Hence, primers targeting the groEL gene were designed and a PCR assay was developed. The PCR products were sequenced and similarity and phylogenetic analysis suggested all these sequences are the groEL gene of A. bovis. In addition, phylogenetic analysis based on the groEL gene also revealed the genetic diversity of A. bovis worldwide, as well as in Shaanxi Province of China, which wasn't reflected by analyzing the rrs gene. In sum, groEL gene is important for molecular detection and phylogenetic analysis of A. bovis.

Molecular identification and characterization of Anaplasma capra and Anaplasma platys-like in Rhipicephalus microplus in Ankang, Northwest China

Background

Four species within Anaplasma genus are emerging zoonotic pathogens, which are transmitted by ticks and generate veterinary and public health concerns. Here, we performed a molecular survey of Anaplasma in Ankang, Northwest China.

Methods

Hard ticks were collected and identified using morphological and molecular methods. Human-pathogenic Anaplasma species were tested using nested polymerase chain reaction. The nearly complete rrs, gltA, and groEL genes sequences from revealed Anaplasma species were amplified and sequenced to determine their molecular characteristics and their phylogeny.

Results

All ticks collected in Ankang belonged to the Rhipicephalus microplus. Novel unclassified Anaplasma strains genetically related to A. platys and A. capra were detected in these ticks. Co-infection of these two organisms was also found. The novel unclassified Anaplasma strains identified in this study formed a distinct phylogenetic lineage based on the groEL gene and two lineages based on the gltA gene within A. platys and related strains group. The revealed A. capra strains identified in this study were most closely related to those detected in humans and other vertebrate animals.

Conclusion

We revealed the presence of A. capra, a novel human pathogens in R. microplus ticks in previously unrecognized endemic regions. We also detected a novel unclassified Anaplasma species genetically related to A. platys. The epidemiology of anaplasmosis caused by these two Anaplasma species in humans should be assessed in future studies.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4075-3) contains supplementary material, which is available to authorized users.

Molecular investigation of tick-borne infections in cattle from Xinjiang Uygur Autonomous Region, China

Tick-borne diseases cause significant losses to livestock production in tropical and subtropical regions. However, information about the tick-borne infections in cattle in Xinjiang Uygur Autonomous Region (XUAR), northwestern China, is scarce. In this study, nested polymerase chain reaction (PCR) assays and gene sequencing were used to detect and analyze epidemiological features of Babesia bovis, B. bigemina, Coxiella burnetii and Anaplasma bovis infections in XUAR. Out of 195 samples tested, 24 (12.3%), 67 (34.4%), 40 (20.5%) and 10 (5.1%) were positive for B. bovis, B. bigemina, C. burnetii and A. bovis, respectively. Sequencing analysis indicated that B. bovis SBP-4, B. bigemina Rap1a, C. burnetii htpB and A. bovis 16S rRNA genes from XUAR showed 99%-100% identity with documented isolates from other countries. Phylogenetic analyses revealed that B. bovis SBP-4, B. bigemina Rap1a, C. burnetii htpB and A. bovis 16S rRNA gene sequences clustered in the same clade with isolates from other countries. To the best of our knowledge, this is the first report of C. burnetii infection of cattle in XUAR. Furthermore, this study provides important data for understanding the distribution of tick-borne pathogens, and is expected to improve the approach for prevention and control of tick-borne diseases in China.

Molecular characterization of Anaplasma and Ehrlichia in ixodid ticks and reservoir hosts from Palestine: a pilot survey

Tick-borne anaplasmosis and ehrlichiosis are clinically important emerging zoonoses usually overlooked by veterinarians and physicians alike. This study aimed at detecting and genetically characterizing Ehrlichia and Anaplasma species in ixodid ticks and their animal hosts from the West Bank, Palestine. A total of 723 ixodid ticks belonging to three genera (Rhipicephalus, Hyalomma, Haemaphysalis) were collected from dogs, sheep, goats and camels. In addition, 189 blood samples were collected from dogs, sheep, camels, horses and a goat from the West Bank, Palestine. All tick and blood samples were investigated for the presence of Anaplasma and Ehrlichia targeting a 345 bp fragment of the 16S rRNA gene followed by sequence analysis. The infection rate of Anaplasma spp. in ticks was 6.5% (47/723). Anaplasma platys was identified in 28% (13/47) of them. Whereas, based on a partial sequence (851 bp) of msp4 gene, 38% (18/47) were identified as A. ovis. The species of the remaining 16 positive samples (16/47, 34%) could not be identified. Simultaneously, the infection rate of Ehrlichia spp. in the ticks was 0.6% (4/723). Three of which were E. canis and one was Ehrlichia spp. The infection rate of A. platys in dogs' blood samples was 10% (13/135), while it was 1.5% (2/135) for E. canis. The infection rate of Anaplasma in sheep blood samples was 40% (19/47), out of which 26% (5/19) were caused by A. ovis as revealed by msp4-PCR. Implementation of purely-spatial analysis by saTScan for all cases of Anaplasma revealed two statistically significant clusters in two districts; Tubas town and Majdal-Bani-Fadil village on the western hills of the Jordan Valley. Most cases of Anaplasma (83%) were from rural areas where life cycle components (vector, host and reservoir) abundantly interact. This study is the first in Palestine to reveal the presence of Anaplasma and Ehrlichia in ticks, dogs and sheep providing crucial platform for future epidemiological surveys and control strategies in the country and region.

Anaplasma bovis infection in a horse: First clinical report and molecular analysis

A 23-year-old male Thoroughbred horse at the Korean Military Academy appeared thin with visible rib bones and presented clinical signs of fever, anorexia, lethargy, and severe dehydration. To determine the presence of various febrile disease-causing agents, the 23 cohabiting horses at the academy, including this horse, were subjected to hematology, blood chemistry, and molecular analysis using whole blood samples collected during regular medical check-ups. On the basis of clinical history, physical examination, hematology, blood chemistry, and fecal examination, differential diagnosis using molecular analyses was performed for various febrile disease-causing agents, including Lyme borreliae, Coxiella, piroplasms (Babesia and Theileria), Rickettsiales (Anaplasma, Ehrlichia, and Rickettsia), equine herpesvirus, equine infectious anemia virus, and equine arteritis virus. While other pathogens were not detected, PCR and phylogenetic analysis targeting the Anaplasma 16S rRNA gene revealed that the horse was infected with Anaplasma bovis. Although PCR targeting the groEL and gltA genes of A. bovis was not successful, the restriction enzyme fragment length polymorphism assay for differential diagnosis and determination of coinfectivity between Anaplasma phagocytophilum and A. bovis confirmed the pathogen as A. bovis. To the best of our knowledge, this is the first clinical report of A. bovis infection in a horse, suggesting a new reservoir host.

Molecular detection of spotted fever group rickettsiae in hard ticks, northern China

Spotted fever group (SFG) rickettsiae are important causative agents of (re)emerging tick-borne infectious diseases in humans, and ticks play a key role in their maintenance and transmission. In this study, hard ticks were collected from five sampling sites in North China in 2017 and 2018. Of them, Haemaphysalis longicornis, Rhipicephalus microplus and Dermacentor nuttalli were collected from livestock (sheep and goats) and the vegetation, Hyalomma asiaticum from sheep, goats and camels, and Hyalomma marginatum from sheep and goats. The SFG rickettsiae were identified in these ticks by amplifying the partial rrs and complete 17-kDa genes, with an overall infection rate of 52.9%. In addition, the nearly full-length rrs and gltA and partial ompA genes were recovered to classify the species of SFG rickettsiae further. Phylogenetic analysis revealed the presence of three human pathogenic species in Hy. asiaticum, Hy. marginatum, Ha. longicornis and De. nuttalli, including two cultured ones (Rickettsia raoultii and Rickettsia aeschlimannii) and one uncultured (Candidatus R. jingxinensis). Furthermore, partial groEL gene was also obtained, and phylogenetic trees were also reconstructed to better understand the genetic relationship with known sequences in each SFG rickettsiae species detected in the current study. Notably, the R. aeschlimannii sequences described in this study were closely related to those from abroad rather than from another part of China, indicating their different origin. However, the R. raoultii and Ca. R. jingxinensis sequences presented close relationship with variants from other parts of China. In sum, our data revealed SFG rickettsiae species in northern China, highlighting the need for surveillance of their infection in local humans.

Characterization of microbiota diversity of field-collected Haemaphysalis longicornis (Acari: Ixodidae) with regard to sex and blood meals

Haemaphysalis longicornis is a prominent tick species in China, and the major vector of an emerging tick-borne disease: severe fever with thrombocytopenia syndrome (SFTS). Microbiome diversity of ticks is influenced by several factors. In this study, we investigated microbiome diversity in field-collected female and male H. longicornis ticks and compared the microbial composition of fed and unfed ticks and of those feeding on different hosts using barcode sequencing of V3-V4 region of 16S RNA gene. Regardless of sex, host, and feeding status; the highest abundance among all samples was found for the genus Coxiella. The relative numbers of Coxiella sequences decreased with the length of the blood feeding, whereas the numbers of Staphylococcus and Corynebacterium increased gradually. The dominance of Coxiella across all samples indicates that it is an obligate symbiont of H. longicornis. Overall, higher microbiome richness was detected in male ticks than in female ticks. Fed ticks showed a more diverse microbe composition than unfed ticks, and ticks fed on goats exhibited the highest diversity. These findings of this study can serve as a basis for future studies of microbiota biology and interactions between the microbes and pathogens of H. longicornis.

Human-pathogenic Anaplasma spp., and Rickettsia spp. in animals in Xi'an, China

In China, thirteen species of tick-borne rickettsiales bacteria pathogenic to human have been reported in ticks and host animals, and human patients caused by them also has been identified. However, investigation for rickettsiales bacteria circulating in Xi'an wasn't performed although diseases resembling human diseases caused by these organisms have been found. In this study, domestic animals and ticks in Xi'an, China, were tested for the presence of rickettsiales bacteria pathogenic to humans. Besides A. ovis, a high prevalence of A. capra was observed suggesting a high public health risk exists. In addition, two novel Anaplasma species closely related to A. phagocytophilum were identified and formed distinct lineages in the phylogenetic trees, with more than 98.3% identities for rrs gene, while divergences up to 20.2% and 37.0% for groEL and gltA genes, respectively. Both of these two novel Anaplasma species were found to circulate in goats and further assessment of their pathogenicity is needed. Ca. R. jingxinensis, with potential pathogenicity, was also detected in H. longicomis ticks with high prevalence. However, other causative agents were not identified although they were distributed in other areas of China.

Molecular detection of Anaplasma phagocytophilum-like Anaplasma spp. and pathogenic A. Phagocytophilum in cattle from South Korea

Anaplasma phagocytophilum is the causative agent of human granulocytic anaplasmosis and tick-borne fever in domestic ruminants. Differential diagnosis of zoonotic and pathogenic tick-borne diseases like granulocytic anaplasmosis is important for the efficient implementation of control programs. Thus, the differentiation of pathogenic A. phagocytophilum from non-pathogenic A. phagocytophilum-like (APL) Anaplasma spp. is essential. Recent molecular analyses of APL revealed its distinct phylogenetic position from A. phagocytophilum. This study was conducted to detect A. phagocytophilum and genetically related strains in 764 cattle in South Korea using PCR and restriction fragment length polymorphism assays. APL clade A and A. phagocytophilum were identified in 20 (2.6%) and 16 (2.1%) cattle, respectively, with 16 cattle (2.1%) displaying co-infection. The 16S rRNA sequences of APL clade A were similar (98.3-99.9%) to those clustered in the APL clade A from eastern Asia. The A. phagocytophilum 16S rRNA sequence shared 98.6-100% identity to those of the A. phagocytophilum group. We used PCR to amplify the groEL and msp2 genes from the 20 samples positive for the 16S rRNA gene and found that 16 were positive for the groEL sequences in the APL clade A, which showed identity (82.8-84.4%) to those clustered in the APL clade A from Japan. Amplification of msp2 was unsuccessful. The co-infection results suggested sequence diversity in Anaplasma spp. Till date, both A. phagocytophilum and APL have been reported to be distributed separately in several animals throughout South Korea. This report is the first co-detection of A. phagocytophilum and APL in Korean cattle using molecular methods. Further studies are needed to provide additional molecular background and trace the evolutionary tree of Anaplasma species in animals and ticks.

Landscape of emerging and re-emerging infectious diseases in China: impact of ecology, climate, and behavior

For the past several decades, the infectious disease profile in China has been shifting with rapid developments in social and economic aspects, environment, quality of food, water, housing, and public health infrastructure. Notably, 5 notifiable infectious diseases have been almost eradicated, and the incidence of 18 additional notifiable infectious diseases has been significantly reduced. Unexpectedly, the incidence of over 10 notifiable infectious diseases, including HIV, brucellosis, syphilis, and dengue fever, has been increasing. Nevertheless, frequent infectious disease outbreaks/events have been reported almost every year, and imported infectious diseases have increased since 2015. New pathogens and over 100 new genotypes or serotypes of known pathogens have been identified. Some infectious diseases seem to be exacerbated by various factors, including rapid urbanization, large numbers of migrant workers, changes in climate, ecology, and policies, such as returning farmland to forests. This review summarizes the current experiences and lessons from China in managing emerging and re-emerging infectious diseases, especially the effects of ecology, climate, and behavior, which should have merits in helping other countries to control and prevent infectious diseases.

Molecular evidence of tick-borne pathogens in Hyalomma anatolicum ticks infesting cattle in Xinjiang Uygur Autonomous Region, Northwestern China

Although tick-borne pathogens have been widely reported in ticks in China, there is little information available on the prevalence of information in Hyalomma ticks from cattle. This study aims to determine the occurrence of pathogens in Hyalomma anatolicum collected from cattle in Xinjiang Uygur Autonomous Region, China, by PCR, sequencing and phylogenetic analysis. Borrelia burgdorferi s.s., Rickettsia massiliae and Anaplasma bovis were identified, whereas DNA of Ehrlichia species and an Anaplasma platys-like pathogen were also detected. Our findings highlight the risk of infection of animals and humans with these pathogens in north-western China.

Rickettsial seropositivity in the indigenous community and animal farm workers, and vector surveillance in Peninsular Malaysia

Rickettsioses are emerging zoonotic diseases that are often neglected in many countries in Southeast Asia. Rickettsial agents are transmitted to humans through exposure to infected arthropods. Limited data are available on the exposure of indigenous community and animal farm workers to the aetiological agents and arthropod vectors of rickettsioses in Peninsular Malaysia. Serological analysis of Rickettsia conorii and Rickettsia felis was performed for 102 individuals from the indigenous community at six rural villages and 87 workers from eight animal farms in Peninsular Malaysia in a cross-sectional study. The indigenous community had significantly higher seropositivity rates for R. conorii (P<0.001) and R. felis (P<0.001), as compared to blood donors from urban (n=61). Similarly, higher seropositivity rates for R. conorii (P=0.046) and R. felis (P<0.001) were noted for animal farm workers, as compared to urban blood donors. On the basis of the sequence analysis of gltA, ompA and ompB, various spotted fever group rickettsiae closely related to R. raoultii, R. heilongjiangensis, R. felis-like organisms, R. tamurae, Rickettsia sp. TCM1, R. felis, Rickettsia sp. LON13 and R. hulinensis were identified from tick/flea samples in animal farms, indigenous villages and urban areas. This study describes rickettsial seropositivity of the Malaysian indigenous community and animal farm workers, and provides molecular evidence regarding the presence of rickettsial agents in ticks/fleas infesting domestic animals in Peninsular Malaysia.

Extensive diversity of rickettsiales bacteria in ticks from Wuhan, China

Rickettsiales bacteria are important agents of (re)emerging infectious diseases, with ticks playing a key role in their evolution and transmission. We collected 1079 hard ticks belonging to five species (Ixodes sinensis, Rhipicephalus microplus, Haemaphysalis flava, Haemaphysalis hystricis and Haemaphysalis longicornis) from cattle and goats in Wuhan city, Hubei province, China. The dominant tick species was H. longicornis (578, 53.57%), followed by R. microplus (354, 32.81%), H. hystricis (62, 5.75%), H. flava (57, 5.28%), and I. sinensis (28, 2.59%). Rickettsiales bacteria were identified in these ticks by amplifying the Rickettsiales 16S rRNA (rrs), citrate synthase (gltA), and heat shock protein (groEL) genes. The rrs gene of Rickettsiales was positive in 32 (2.97%) ticks, including 2 cases of co-infection, with 4 (0.69%) in H. longicornis, 15 (4.24%) in R. microplus, 7 (12.28%) in H. flava, 1 (1.61%) in H. hystricis, and 5 (17.86%) in I. sinensis ticks. Phylogenetic analysis revealed the presence of six recognized and seven Candidatus species of Rickettsiaceae, Anaplasmataceae and Candidatus Midichloriaceae. Notably, one lineage within both Ehrlichia and Candidatus Midichloriaceae was distinct from any known Rickettsiales, suggesting the presence of potentially novel species of Rickettsiales bacteria. In sum, these data reveal an extensive diversity of Rickettsiales in ticks from Wuhan, highlighting the need to understand Rickettsiales infection in local animals and humans.

Extensive genetic diversity of Rickettsiales bacteria in multiple mosquito species

Rickettsiales are important zoonotic pathogens, causing severe disease in humans globally. Although mosquitoes are an important vector for diverse pathogens, with the exception of members of the genus Wolbachia little is known about their role in the transmission of Rickettsiales. Herein, Rickettsiales were identified by PCR in five species of mosquitoes (Anopheles sinensis, Armigeres subalbatus, Aedes albopictus, Culex quinquefasciatus and Cu. tritaeniorhynchus) collected from three Chinese provinces during 2014–2015. Subsequent phylogenetic analyses of the rrs, groEL and gltA genes revealed the presence of Anaplasma, Ehrlichia, Candidatus Neoehrlichia, and Rickettsia bacteria in mosquitoes, comprising nine documented and five tentative species bacteria, as well as three symbionts/endosybionts. In addition, bacteria were identified in mosquito eggs, larvae, and pupae sampled from aquatic environments. Hence, these data suggest that Rickettsiales circulate widely in mosquitoes in nature. Also of note was that Ehrlichia and Rickettsia bacteria were detected in each life stage of laboratory cultured mosquitoes, suggesting that Rickettsiales may be maintained in mosquitoes through both transstadial and transovarial transmission. In sum, these data indicate that mosquitoes may have played an important role in the transmission and evolution of Rickettsiales in nature.

Molecular epidemiological surveillance to assess emergence and re-emergence of tick-borne infections in tick samples from China evaluated by nested PCRs

An investigation was performed to detect eight pathogens in ticks collected from grass tips or animals in the southern, central and northeast regions of China. DNA samples extracted from ticks were collected from ten different locations in eight provinces of China and subjected to screening for tick-borne pathogens, including Borrelia burgdorferi sensu lato, Ehrlichia spp., Rickettsia spp., Babesia/Theileria spp., Ehrlichia ruminantium, Coxiella burnetii, and Francisella tularensis, using nested PCR assays and sequencing analysis. The results indicated that Borrelia spp., Rickettsia spp., and Babesia/Theileria spp. were detected in all of the investigated provinces. Ehrlichia spp. was also found in all of the surveyed areas, except Guangxi, Luobei and Tonghe counties in Heilongjiang province. The average prevalence of these pathogens was 18.4% (95% CI=12.8-42.5), 60.3% (95% CI=18.2-65.3), 26.0% (95% CI=25.8-65.1), and 28.7% (95% CI=5.6-35.2), respectively. A sequencing analysis of the pCS20 gene of E. ruminantium revealed an E. ruminantium-like organism (1/849, 0.1%, 95% CI=0-0.3) in one tick DNA sample extracted from Rhipicephalus (Boophilus) microplus in Hunan. In addition, Borrelia americana in Ixodes persulcatus, Babesia occultans in Haemaphysalis qinghaiensis and both Rhipicephalus sanguineus and an Ehrlichia muris-like organism in R. (B.) microplus was detected, possibly for the first time in China. Four DNA sequences closely related to Borrelia carolinensis and/or Borrelia bissettii from Haemaphysalis longicornis, Candidatus Rickettsia principis from H. qinghaiensis, and I. persulcatus and Ehrlichia canis (named E. canis-like) from Haemaphysalis bispinosa were also detected in this work.

Emerging tick-borne infections in mainland China: an increasing public health threat

Since the beginning of the 1980s, 33 emerging tick-borne agents have been identified in mainland China, including eight species of spotted fever group rickettsiae, seven species in the family Anaplasmataceae, six genospecies in the complex Borrelia burgdorferi sensu lato, 11 species of Babesia, and the virus causing severe fever with thrombocytopenia syndrome. In this Review we have mapped the geographical distributions of human cases of infection. 15 of the 33 emerging tick-borne agents have been reported to cause human disease, and their clinical characteristics have been described. The non-specific clinical manifestations caused by tick-borne pathogens present a major diagnostic challenge and most physicians are unfamiliar with the many tick-borne diseases that present with non-specific symptoms in the early stages of the illness. Advances in and application of modern molecular techniques should help with identification of emerging tick-borne pathogens and improve laboratory diagnosis of human infections. We expect that more novel tick-borne infections in ticks and animals will be identified and additional emerging tick-borne diseases in human beings will be discovered.