The previous studies revealed the dominant species are R. sanguineus and R. microplus in Hainan Island, China , as well as in our study. Hainan Island is the natural epidemic focus of North Asia Tick-Borne Spotted Fever (NASF) . The antibodies investigate of NASF in local human and mouse indicated the positive incidence are high . In the current study we evaluated the presence of several pathogens as Rickettsiales bacteria, Coxiellaceae bacteria, Babesiidae, and Hepatozoidae in these two ticks. The results revealed the presence of four recognized species and two Candidatus sp. of Anaplasmataceae and Coxiellaceae. Importantly, A. marginale, A. platys, H. canis, B. canis, and Coxiella burnetii are known to be animal and/or human pathogens [28, 30]. Hence, the data clearly indicate that multiple bacteria and protozoa co-circulate in hard ticks in Hainan Island. As more species of ticks are present in Hainan Island, it is likely that more additional tick-associated pathogens will be discovered.
Many members in the family Anaplasmataceae are causative agents of tick-borne diseases (i.e. Anaplasmosis and Ehrlichiosis) with a remarkable impact on human and animal health . Several species have been identified in family Anaplasmataceae and some are considered as human or animal pathogens. For example, A. phagocytophilum, A. marginale, and A. platys are the important disease-producing pathogens in the genus Anaplasma [5, 32]. A. marginale is the common ruminant pathogens infecting buffalo and cattle which is distributed on six continents, especially in tropical and subtropical regions [30, 33, 34]. While A. platys is the agent of cyclic thrombocytopenia in dogs and is the only classified Rickettsiales species known to infect platelets . Besides infecting dogs, the infection of this pathogen has been reported in cats, foxes (Vulpes vulpes), cattle, goats, camels, red deer, and humans [8, 25, 35–42]. In our study, two documented bacteria A. marginale and A. platys were identified in R. microplus and R. sanguineus ticks separately. The cattle, as the major hosts of R. microplus, possessed the high prevalence of A. marginale, and these results suggests that more surveillance in cattle in Hainan Island needs to be performed. R. sanguineus is considered the primary vector of infection to A. platys, which is all founded in dogs in this study. However, the high infection rate of A. platys in local dog ticks indicated high risk of cyclic thrombocytopenia to other animals and humans, due to the close exposure between the dogs and others. Therefore, more surveillance and researches in dogs and its pathogens in Hainan Province needs to be performed.
Similar to the Anaplasma, several novel Ehrlichia bacteria has been discovered in the past decade [17, 31, 33]. Here, a tentative species was identified in R. microplus ticks from cattle, which is mainly founded in R. microplus ticks from several provinces and countries [12, 26, 27, 43]. Otherwise, the sequence of this candidatus species are close to that of E. chaffeensis which is human pathogen bacteria, so more attentions would be paid to this potential novel species.
Coxiella burnetii is the causative agent of Q fever which is a worldwide zoonosis. In common, the infection is mostly persistent in animals, whereas it is often asymptomatic in humans, which can manifest as an acute disease like a flu-like illness, or pneumonia, or as a chronic form like endocarditis, et al . There are not typical symptoms when infection occurred in animals and humans except during pregnancy. The most primary reservoirs of C. burnetii are goats, sheep, and cattle . In nature, the ticks, as the main vector and reservoir, play important part in the bacteria maintaining and transmitting, otherwise the cattle and goats play the most important roles in human infections. In this study, Coxiella like bacteria were identified in 3 R. sanguineus ticks sampled from Hainan. It would be paid more attentions to due to its closer relations with the known Coxiella burnetii.
Canine hepatozoonosis is a tick-borne disease distributed worldwide, and H. canis is the etiology of hepatozoonosis in dogs . Canine babesiosis is a vector-borne disease caused by several Babesia spp. like B. canis vogeli et al . In our study, H. canis and B. canis vogeli were identified in 3 and 1 R. sanguineus ticks collected from Hainan Island, separately. These data revealed that the two agents are co-circulating in arthropods, and the infection risk is higher for dogs, as well as other animals in certain regions.