Molecular detection of Bartonella in ixodid ticks and plateau pika (Ochotona curzoniae) in Shiqu County, China

Background: Bartonella bacteria have been associated with an increasingly wide range of human and animal diseases. They were identified as being globally dispersed as emerging pathogens. Ticks and small rodents are known as hosts of human and animal bartonellosis. They play a significant role in the preservation and circulation of bartonellae in nature. This study investigates the occurrence of Bartonella spp. in ticks and plateau pika in Shiqu county which is located on the Eastern Qinghai-Tibetan plateau in China. Shiqu county is spread over approximately 26,000 square kilometers, with an average altitude of above 4,200 meters and vast area of pastureland.Results: A total of 818 ticks (Dermacentor everestianus, 79.0%, 646/818; Haemphysalis qinghaiensis, 21.0%, 172/818) were collected 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 Bartonella spp. in ticks from Arizha, Maga, Derongma, and Changxgma were 4.8%, 76.8%, 12.5%, and 18.0% respectively. The infection rate of Bartonella spp. in Maga was higher (p< 0.01) than in other villages. Regarding plateau pika, the total infection rate of Bartonella spp was 24.1%, with 20.8% (15/72), 30.9% (25/81), 13.8% (9/65), and 29.4% (20/68) in Arizha, Maga, Derongma, and Changxgma respectively. Finally, B. queenslandensis, B. grahamii, and two unvalidated Bartonella species were detected. 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 the public health should be closely monitored.

Moleculare detection of Bartonella in ixodid ticks and plateau pika (Ochotona curzoniae) in Shiqu county, China

Background Bartonella bacteria have been associated with an increasingly wide range of human and animal diseases and were also recognized to be globally dispersed as emergent pathogens. Ticks and small rodents are known vectors of human and animal bartonellosis and play important roles in maintenance and circulation of bartonellae in nature. In China, Shiqu county is located on the eastern Qinghai-Tibetan plateau and about 26 thousands square kilometers with an average altitude of above 4,200 meters and vast area of pastureland. In present study, the occurrence of Bartonella spp. in ticks and plateau pika was firstly investigated in Shiqu county.Results A total of 818 ticks ( Dermacentor everestianus , 79.0%, 646/818; Haemphysalis qinghaiensis , 21.0%, 172/818), were collected in 4 villages in Shiqu county. Only Bartonella melophagi was detected in tick samples with a total prevalence of 30.1% (246/818). Significant difference was observed (P<0.05) between D.everestianus (17.0%) and H.qinghaiensis (79.1%).The infection rates of Bartonella spp. in ticks from Arizha, Maga, Derongma and Changxgma villages were 4.8%, 76.8%, 12.5% and 18.0%, respectively. Compared with other villages, the infection rate of Bartonella spp. in Maga was higher (P<0.01). As for plateau pika, total infection rate of Bartonella spp was 24.1%, with 20.8% (15/72), 30.9% (25/81), 13.8% (9/65) and 29.4% (20/68) in Arizha, Maga, Derongma and Changxgma, respectively. Totally, B. queenslandensis , B.grahamii and two unvalidated Bartonella species were detected. No significant difference in infection rates was observed (P>0.05) between theses study sites. Conclusion At present, only D.everestianus and H.qinghaiensis were found in Shiqu county with high infection of Bartonella spp. in theses ticks and plateau pika. The threats to public health by these Bartonella species should be monitored.

Characterization of the Rickettsia-like and Coxiella-like symbionts in the tick Dermacentor everestianus Hirst, 1926 (Acari: Ixodidae) from the Qinghai-Tibet Plateau

The tick Dermacentor everestianus is widely distributed on the Tibetan Plateau of China, where adult ticks usually parasitize sheep, yaks and horses. D. everestianus is able to transmit many zoonotic pathogens, including Francisella tularensis, Anaplasma ovis and Rickettsia raoultii-like bacteria, and can cause great damage to animals and human health. However, the symbionts in D. everestianus have not yet been investigated, which has hindered our understanding of the relationships between this tick species and associated tick-borne pathogens. In the current study, the Rickettsia-like and Coxiella-like symbionts in D. everestianus were identified and characterized. The results indicated that both Rickettsia-like (RLS-Des) and Coxiella-like (CLS-Des) symbionts showed 100% infection rates and displayed vertical transmission in D. everestianus. The RLS-Des showed a relatively higher abundance than the CLS-Des in D. everestianus. No tissue specificity was found for the RLS-Des or CLS-Des. These symbionts can inhabit the ovaries, salivary glands, midguts, Malpighian tubules and testes of D. everestianus. During the development of D. everestianus, the density of the RLS-Des showed more obvious changes than did that of the CLS-Des. Dramatic changes in the density of the RLS-Des were detected in the midguts, ovaries, salivary glands and Malpighian tubules when female D. everestianus were engorged and detached from the host, which suggested the potential role of these symbionts in the reproduction and development of D. everestianus. The dynamic changes in the density of the CLS-Des during feeding and reproduction of D. everestianus suggest the involvement of the CLS-Des in the reproduction of D. everestianus.

The mitochondrial genome and phylogenetic analysis of the tick Dermacentor everestianus Hirst, 1926 (Acari: Ixodidae)

The tick Dermacentor everestianus is widely distributed in Qinghai-Tibet Plateau of China and can transmit many zoonotic pathogens. In the current study, the complete mitochondrial (mt) genome of D. everestianus was sequenced through Illumina HiSeq sequencing. The mt genome is 15,191 bp in length which contains 37 genes, including 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes. The overall GC content reached 21.20%, whereas the GC content in the gene region was 21.40%, and in the intergenetic region was 20.50%. Two control regions were sequenced from mt genome of D. everestianus, one located between tRNA-Cys and tRNA-Leu, and the other one was found between rrnS and tRNA-Ile. Two tandem repeats were found between tRNA-Glu and nad1. A phylogenetic tree was constructed based on the complete mitogenome of D. everestianus and 32 other ixodid tick mitogenomes to assess their phylogenetic relationships. D. everestianus is phylogenetically clustered with the tick D. silvarum and D. nuttalli. This is the first complete mt genome of D. everestianus, which provides a useful reference for future studies on systematics and population genetics of this tick species.