Molecular detection, diagnostic evaluation, and genetic characterization of blood-borne pathogens in fighting bulls from southern Thailand.

Fighting bulls are native cattle bred for traditional contests with economic and recreational significance in southern Thailand. These animals may be infected with several blood-borne and vector-borne pathogens, including Anaplasma spp., hemotropic Mycoplasma spp. (hemoplasmas), Babesia spp., Theileria spp., and Trypanosoma spp. Blood cytology is commonly used for diagnosis because it is simple and inexpensive; however, its diagnostic performance can be limited, particularly in carrier animals with low parasitemia. This study screened blood-borne pathogens in fighting bulls (n = 198) from southern Thailand using conventional PCR and blood cytology, evaluated the diagnostic performance of blood cytology using PCR as the reference method, and genetically characterized selected PCR-positive samples by sequencing, BLAST analysis, and phylogenetic analysis. PCR-positive rates for Anaplasma spp., hemoplasmas, Babesia spp., Theileria spp., and Trypanosoma spp. were 75.3%, 80.8%, 3.0%, 98.0%, and 0.0%, respectively. PCR detection rates for Anaplasma spp., hemoplasmas, Babesia spp., and Theileria spp. were significantly higher than those obtained by blood cytology. Compared with PCR, blood cytology showed no to slight agreement (kappa < 0.20), sensitivity below 20%, and specificity above 75%. Genetic analyses identified Anaplasma spp., including A. platys-like, A. bovis-like, and Anaplasma sp. closely related to "Candidatus Anaplasma boleense", Mycoplasma wenyonii, "Candidatus Mycoplasma haematobovis", Babesia bigemina, and Theileria sinensis. These findings demonstrate a high occurrence of blood-borne pathogens and indicate that blood cytology substantially underestimates pathogen detection in fighting bulls.