Background Anaplasma, Babesia and Theileria are tick-borne pathogens (TBPs) that affect livestock worldwide. However, information on these pathogens in yaks (Bos grunniens) and Tibetan sheep (Ovis aries) on the Qinghai-Tibet Plateau (QTP), China, is limited. In this study, Anaplasma spp., Babesia spp. and Theileria spp. infections were assessed in yaks and Tibetan sheep from Qinghai Province. Methods A total of 734 blood samples were collected from 425 yaks and 309 Tibetan sheep at nine sampling sites. Standard or nested polymerase chain reaction was employed to screen all the blood samples using species- or genus-specific primers. Results The results showed that 14.1% (60/425) of yaks and 79.9% (247/309) of Tibetan sheep were infected with at least one pathogen. Anaplasma ovis, Anaplasma bovis, Anaplasma capra, Anaplasma phagocytophilum, Babesia bovis and Theileria spp. were detected in this study, with total infection rates for all the assessed animals of 22.1% (162/734), 16.3% (120/734), 23.6% (173/734), 8.2% (60/734), 2.7% (20/734) and 19.3% (142/734), respectively. For yaks, the infection rate of A. bovis was 6.4% (27/425), that of B. bovis was 4.7% (20/425) and that of Theileria spp. was 3.3% (14/425). Moreover, 52.4% (162/309) of the Tibetan sheep samples were infected with A. ovis, 30.1% (93/309) with A. bovis, 56.0% (173/309) with A. capra, 19.4% (60/309) with A. phagocytophilum and 41.4% (128/309) with Theileria spp. Conclusions This study revealed the prevalence of Anaplasma spp., Babesia spp. and Theileria spp. in yaks and Tibetan sheep in Qinghai Province, China, and provides new data for a better understanding of the epidemiology of TBPs in these animals in this area of the QTP, China. Graphical Abstract

Toxoplasma gondii belongs to the Apicomplexan protozoa—an obligate intracellular parasite—causing toxoplasmosis that has a worldwide distribution and is very harmful to both human health and the livestock industry. However, the information on toxoplasmosis in the Qinghai-Tibetan Plateau Area (QTPA) and the seroprevalence of T. gondii in the food-borne animals in that area has been limited. Therefore, this study focused to T. gondii and toxoplasmosis to perform an indirect ELISA test based on recombinant TgSAG2 protein to establish a comprehensive record of the seroprevalence of T. gondii infections in a wide range of animals, including Tibetan sheep (Ovis aries), yaks (Bos grunniens), cows, chicken, pigs, and horses, in the QTPA. Overall, the seropositive rates of the specific-T. gondii IgG and IgM antibodies in all investigated animals were 44.1% (1179/2673) and 18.0% (469/2612), respectively. The 14.9% (389/2612) sera were determined to be both IgG and IgM positive samples, 30.2% (789/2673) were single-IgG seropositive, and a total of 80 in 2612 animals (3.0%) were single-IgM seropositive. Moreover, for the animal species, the pig was the most prevalent animal (90.2%, 304/337) for IgG positivity, followed by Tibetan sheep (50.7%, 460/907), chickens (45.8%, 229/500), yaks (21.1%, 140/663), cows (18.5%, 38/205) and horses (13.1%, 8/61), respectively. For the IgM antibody positivity, the pig was also the most prevalent animal (41.8%, 141/337), followed by Tibetan sheep (21.2%, 191/907), cows (15.1%, 31/205), chickens (12.4%, 62/500) and yaks (6.6%, 44/663), respectively. The significant differences in the prevalent distribution of T. gondii were found in the different altitudes. In conclusion, this study found the high seroprevalence for T. gondii infections among these animal species in the QTPA, and provides new data to facilitate further research for development of control measures against T. gondii infections in the surveyed locations.

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.