Serological Analysis of IgG and IgM Antibodies against Anaplasma spp. in Various Animal Species of the Qinghai-Tibetan Plateau

SIMPLE SUMMARY: Tick-borne pathogens are considered emergent because they cause several tick-borne diseases that threaten the health of humans and animals during tick feeding, including anaplasmosis, which is caused by Anaplasma spp. However, information on the carrier animals for Anaplasma spp. antibodies in the Qinghai–Tibetan Plateau Area is limited, and current data on the serodetection of anaplasmosis in plateau areas around the world are needed. Indirect ELISA and competitive ELISA are reliable serological tests that have been developed for the detection of Anaplasma infections in animals. Moreover, major surface protein 5 is a highly conserved surface protein of the Anaplasma genus that has proven effective as a diagnostic antigen and has been used in the serodetection of Anaplasma species infection in various animals with a high level of sensitivity. Hence, in this study, an rMSP5-ELISA was performed to analyze Anaplasma spp. IgG and IgM antibodies in potential carrier animals in the Qinghai–Tibetan Plateau Area. The results not only show the positive rate of IgG and IgM antibodies in the study animals but also indicate that there is a threat of tick biting and zoonotic pathogen infection in the vicinity of human activities in the tested areas. Our study should have major importance for identifying animals with Anaplasma spp. infection in the plateau area. ABSTRACT: Anaplasma genus infects the blood cells of humans and animals by biting, causing zoonotic anaplasmosis. However, limited data are available on carrier animals for Anaplasma spp. antibodies in the Qinghai–Tibetan Plateau Area. Therefore, a serological indirect ELISA diagnostic method based on the major surface protein 5 (MSP5), derived from Anaplasma phagocytophilum, was developed in this study to analyze both IgG and IgM antibodies of Anaplasma spp. in a total of 3952 animals from the Qinghai–Tibetan Plateau, including yaks (Bos grunniens), cows (Bos taurus), cattle (Bos taurus domesticus), Tibetan sheep (Ovis aries), horses (Equus ferus caballus), pigs (Sus domesticus), chickens (Gallus gallus domesticus), donkeys (Equus asinus), stray dogs (Canis sp.), and stray cats (Felis sp.). The results showed that recombinant MSP5 protein was expressed and was successfully used to establish the indirect ELISA methods. The overall positivity for Anaplasma IgG and IgM antibodies was 14.6% (578/3952) and 7.9% (312/3952), respectively, and a total of 123 animals (3.1%) were both IgG- and IgM-positive. Moreover, the most prevalent Anaplasma IgG positivity was exhibited by donkeys (82.5%), followed by stray dogs, Tibetan sheep, pigs, chickens, horses, yaks, cows, cattle, and stray cats. The analysis for IgM antibody positivity revealed that IgM positivity was the most prevalent in the stray dogs (30.1%), followed by horses, yaks, Tibetan sheep, cows, stray cats, and cattle. Moreover, the results revealed significant differences (p < 0.05) at different altitudes in Anaplasma-specific IgG in the yaks, Tibetan sheep, and horses, and in IgM in the yaks and Tibetan sheep. In conclusion, this study is the first to demonstrate that yaks, cows, cattle, Tibetan sheep, horses, donkeys, stray dogs, stray cats, pigs, and chickens living in the Qinghai–Tibet Plateau are carrier animals for Anaplasma spp. IgG or IgM antibodies. The current findings provide valuable current data on the seroepidemiology of anaplasmosis in China and for plateau areas of the world.