Molecular Detection and Phylogenetic Analysis of Vector-Borne Pathogens from Melophagus ovinus in Qinghai, China.

Vector-borne pathogens, predominantly transmitted through arthropod vectors, present a major threat to both livestock production and public health. Melophagus ovinus is a significant disease vector widely distributed across various pastoral regions in China. However, there has been limited research on the prevalence of vector-borne pathogens within M. ovinus populations in Qinghai Province, China. In this study, a total of 433 M. ovinus specimens were collected from Haixi and Hainan prefectures in Qinghai Province between 2024 and 2025. After identifying the parasites via morphological and molecular approaches, the specimens were grouped into 84 pools and tested for the presence of three vector-borne pathogens using PCR techniques. The findings indicated that all collected specimens exhibited morphological features consistent with M. ovinus, and the 18S rRNA gene sequences of the selected parasites (n = 7) demonstrated sequence similarities ranging from 99.1% to 100% relative to reference M. ovinus strains. Among the 84 M. ovinus pools analyzed, 68 tested positive for Bartonella spp. DNA; subsequent genetic characterization identified these isolates (n = 15) as Bartonella melophagi. Additionally, Rickettsia spp. DNA was detected in 18 pools (21.43%), genetic characterization based on the OmpA gene (n = 6) identified all as Rickettsia conorii. No DNA from Babesia spp. or Theileria spp. was detected in any of the pool. Collectively, this investigation elucidates the epidemiological characteristics of three vector-borne pathogens among M. ovinus populations in Qinghai, China, and provides the first evidence of a high prevalence of both B. melophagi and R. conorii, emphasizing the necessity for targeted prevention and control measures.