Dermacentor everestianus Hirst, 1926 (Acari: Ixodidae): phylogenetic status inferred from molecular characteristics

High prevalence of spotted fever group rickettsiae in ticks collected from yaks (Bos grunniens) in Shiqu county, eastern Tibetan Plateau, China

Tick-borne diseases have become a global health concern in recent decades. Spotted fever group (SFG) rickettsiae have been recognized as important pathogens of human tick-borne diseases worldwide. In this study, Dermacentor everestianus (n = 646) and Haemaphysalis qinghaiensis (n = 172) ticks were collected from yaks (Bos grunniens) in Shiqu county, eastern Tibetan Plateau, China. SFG rickettsiae were identified and characterized in these ticks. A total of 49.9% (408/818) ticks were infected by Rickettsia spp. with infection rates of 58.1% (100/172) and 46.7% (308/646) detected in H. qinghaiensis and D. everestianus ticks, respectively. Furthermore, 95% of Rickettsia spp. were Rickettsia raoultii-like bacteria, and 5% were related to Candidatus Rickettsia longicornii. To the best of our knowledge, this is the first time that SFG rickettsiae infections were firstly reported in Shiqu county for these tick species. Our results indicated that H. qinghaiensis and D. everestianus ticks from Shiqu county became highly infected with a R. raoultii-like bacteria during their feeding process. This observation is alarming because of the zoonotic potentiality of these species. Overall, the present study detected a widespread of R. raoultii-like bacteria in ticks that are considered a serious threat to domestic animals and humans in Shiqu county. The prevalence of R. raoultii-like bacteria in human and wildlife hosts should be further investigated in the future.

Tick distribution and detection of Babesia and Theileria species in Eastern and Southern Kazakhstan

Piroplasmosis is an economically important tick-borne disease worldwide. However, little is known about the presence of Babesia spp. and Theileria spp. in ticks in Eastern and Southern Kazakhstan (ESK). During 2016 - 2019, adult ticks (at 26 sampling sites in 16 districts of 5 oblasts in ESK) were collected. Tick species were identified according to morphological and molecular characteristics. Two fragments (487 bp and 438 bp) of 18S ribosomal RNA (18S rRNA) were used to determine piroplasm species in representative 698 ticks. The genotype characteristics of Babesia caballi and Theileria equi were further analyzed by longer 18S rRNA gene fragments. A total of 6107 adult ticks (4558 parasitizing ticks and 1549 off-host ticks), including 4665 hard ticks and 1442 soft ticks, were collected from their natural hosts (cattle, horses, sheep, camels, shepherd dogs and hedgehogs) and the surrounding environment, respectively. Among the hard tick species, Dermacentor marginatus (62.59%, 2920/4665) was the most abundant, followed by Hyalomma asiaticum (19.36%, 903/4665) and Hyalomma detritum (9.95%, 464/4665). All soft ticks were identified as Argas persicus. 16S ribosomal DNA (16S rDNA) phylogenic analysis showed that several tick species in Kazakhstan, as exemplified by Haemaphysalis erinacei and D. marginatus, clustered together with conspecific ticks reported from China. Five species of piroplasms, i.e. Babesia occultans, Babesia caballi, Theileria ovis, Theileria annulata and Theileria equi, were detected in 698 representative ticks. Genotype E of T. equi in Almaty, and genotype A of B. caballi in Almaty and South Kazakhstan were identified.

Molecular detection of Bartonella in ixodid ticks collected from yaks and plateau pikas (Ochotona curzoniae) in Shiqu County, China

Background

Bartonella bacteria have been associated with an increasingly wide range of human and animal diseases. These emerging pathogens have been identified as being globally dispersed. Ticks and small rodents are known hosts of Bartonella and play a significant role in the preservation and circulation of Bartonella in nature. This study investigated the occurrence of hoist spp. in ticks (Acari: Ixodidae) and plateau pikas (Ochotona curzoniae) in Shiqu County, which is located on the eastern Qinghai-Tibetan Plateau in China. Shiqu County is spread over approximately 26,000 km², with an average altitude of above 4200 m and a vast area of pastureland.

Results

A total of 818 ticks (Dermacentor everestianus, 79.0%, 646/818; Haemaphysalis qinghaiensis, 21.0%, 172/818) were collected from yaks in 4 villages of Shiqu County. Only Bartonella melophagi was detected in tick samples, with a total prevalence of 30.1% (246/818). The infection rates of B. melophagi in ticks from Arizha, Maga, Derongma, and Changxgma were 4.8, 76.8, 12.5, and 18.0%, respectively. The infection rate of B. melophagi in Maga was higher (p < 0.01) than those in other villages. Regarding plateau pikas, the total infection rate of Bartonella spp. was 21.7% (62/286), with 16.7% (12/72), 30.9% (25/81), 13.8% (9/65), and 23.5% (16/68) in Arizha, Maga, Derongma, and Changxgma, respectively. Finally, B. queenslandensis and B. grahamii were detected in plateau pika. No significant difference was observed (p > 0.05) in the infection rates between these study sites.

Conclusion

To date, only D. everestianus and H. qinghaiensis were found in Shiqu County with high infection of Bartonella spp. in the ticks and plateau pika. The threats of Bartonella species to public health should be closely monitored.

Mitochondrial Gene Heterogeneity and Population Genetics of Haemaphysalis longicornis (Acari: Ixodidae) in China

INTRODUCTION

Haemaphysalis longicornis is an important ectoparasite of domestic and wild animals that can transmit many pathogens including viruses, fungi, bacteria and protozoa.

MATERIALS AND METHODS

In this study, we examined genetic variation and population genetics in three mitochondrial (mt) genes [cox1 (cytochrome c subunit 1), rrnL (large subunit ribosomal RNA) and nad5 (NADH dehydrogenase 5)] among four H. longicornis populations from China.

RESULTS

The sizes of the partial sequences of cox1, rrnL and nad5 were 776 bp, 409 bp, 510 bp, respectively. Among the obtained sequences, we identified 22 haplotypes for cox1, 2 haplotypes for rrnL and 17 haplotypes for nad5. Low gene flow and significant genetic differentiation (66.2%) were detected among H. longicornis populations. There was no rapid expansion event in the demographic history of four H. longicornis populations in China. In addition, phylogenetic analyses confirmed that all the Haemaphysalis isolates were H. longicornis which were segregated into two major clades.

CONCLUSION

The mt DNA genes provide a potential novel genetic marker for molecular epidemiology of H. longicornis and assist in the control of tick and tick-borne diseases in humans and animals.

Molecular detection of spotted fever group rickettsiae in ticks parasitizing pet dogs in Shihezi City, northwestern China

A total of 178 adult ticks were collected from 32 pet dogs from five veterinary clinics in Shihezi City, Xinjiang Uygur Autonomous Region (XUAR), northwestern China. All the ticks were identified by comprehensive morphological and genetic analyses, and rickettsiae were detected by seven Rickettsia-specific genetic markers in the ticks. The ticks collected were identified as Rhipicephalus sanguineus sensu lato. Twenty-one of the 178 samples (11.8%) were positive for rickettsiae. Among these, in 13 (61.9%) samples Candidatus R. barbariae were identified, in five (23.8%) samples R. massiliae, and in three (14.3%) samples R. conorii. This study indicates that more attention should be paid to rickettsial infection in pet dogs and their ticks, because the latter may pose an epidemiological risk for tick-borne transmission of rickettsiae to human beings.

Diversity of Rickettsia species in border regions of northwestern China

Background

Rickettsia species belonging to the spotted fever group (SFG) cause infections in humans, domestic animals and wildlife. At least ten SFG Rickettsia species are known to occur in China. However, the distribution of rickettsiae in ticks and fleas in the border region of northwestern China have not been systematically studied to date.

Results

A total of 982 ticks (Rhipicephalus turanicus, Dermacentor marginatus, D. nuttalli and Haemaphysalis punctata) and 5052 fleas (18 flea species from 14 species of wild mammals) were collected in ten and five counties, respectively, of Xinjiang Uygur Autonomous Region (northwestern China). Tick and flea species were identified according to morphological and molecular characteristics. Seven sets of primers for amplifying the 17-kDa antigen gene (17-kDa), citrate synthase gene (gltA), 16S rRNA gene (rrs), outer membrane protein A and B genes (ompA, ompB), surface cell antigen 1 gene (sca1) and PS120-protein encoding gene (gene D) were used to identify the species of rickettsiae. Nine Rickettsia species have been detected, seven of them in ticks: R. aeschlimannii, R. conorii, R. raoultii, Rickettsia sibirica, R. slovaca, R. massiliae and “Candidatus R. barbariae”. In addition, R. bellii and two genotypes of a rickettsia endosymbiont (phylogenetically in an ancestral position to R. bellii) have been detected from flea pools.

Conclusions

This study provides molecular evidence for the occurrence of several SFG rickettsiae in Rhipicephalus turanicus, Dermacentor nuttalli and D. marginatus. Furthermore, R. bellii and two ancestral rickettsia endosymbionts are present in fleas infesting wild rodents in the border regions of northwestern China. These data extend our knowledge on the diversity of rickettsiae in Central Asia.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3233-6) contains supplementary material, which is available to authorized users.

The life cycle and development characteristics of Dermacentor everestianus (Acari: Ixodidae) under field conditions in Qinghai-Tibet Plateau

The tick Dermacentor everestianus mainly distributed in Tibet, China and Nepal, and can transmit some pathogens causing great damages in Qinghai-Tibet Plateau. This study investigated the life cycle and development characteristics of D. everestianus under field conditions. The average duration of the whole life cycle of D. everestianus was 124.4 days, with the host available in the field plot. Under natural conditions, the mean feeding, preoviposition and oviposition period of female ticks were 6.1, 17.9 and 21.2 days, respectively. The incubation time of eggs was the longest phase in the life cycle of the ticks (26 days on average). Moreover, the weight of engorged females was highly positively correlated with the number of the eggs that were laid (r = 0.81, P < 0.05). The reproductive efficiency index and reproductive fitness index in females were 7.3 and 5.9, respectively. The above findings suggest that the tick D. everestianus have evolved well adaptability to the highland areas.

Morphological and molecular divergence of Rhipicephalus turanicus tick from Albania and China

Rhipicephalus turanicus is an important tick species potentially carrying tick-borne pathogens. Several tick species have obvious subspecies divergence. However few studies aimed to examine the existence of divergence within R. turanicus. Therefore, a detailed morphological and molecular analysis was conducted for comparing R. turanicus from the Mediterranean Basin (represented by Albania) and Central Asia (Northwestern China). Altogether 315 adult ticks of R. turanicus (103 from Albania and 212 from China) were morphologically and molecularly analysed. DNA samples were used for mitochondrial 16S rRNA and cox1 gene sequences analysis. In addition, as potentially genetic markers, three fragments including partial nad1-16S rRNA, nad2-cox1, cox1-tRNA-Lys, were designed and then phylogenetically analyzed. Based on detailed morphological observations, only basis capituli length:width ratio (females), the length, the width and the length:width ratio of the scutum (males) had differences between R. turanicus from China and Albania. Gene divergences of 16S rRNA, cox1, partial nad1-16S rRNA, nad2-cox1 and cox1-tRNA-Lys from China and Albania ticks were 3.53-4.84, 3.57-4.92, 3.57-4.07, 3.57-4.39 and 3.18-4.69%, respectively. The evaluated five genetic markers revealed two phylogenetic branches in R. turanicus. Obvious differences exist within R. turanicus based on morphological and genetic analysis. Three newly designed genetic markers (partial nad1-16S rRNA, nad2-cox1 and cox1-tRNA-Lys) in this study may be suitable genetic tools for identification and analysis in R. turanicus. Subspecies analysis of R. turanicus from other regions of the world should be initiated in the future.