Two divergent hemoplasma lineages within the Mycoplasma wenyonii complex in dairy cattle from Thailand revealed by comparative analyses of partial 16S and 23S rRNA gene sequences

Abstract Background Dairy cattle are important livestock in Thailand and may be affected by infectious agents, including hemotropic Mycoplasma spp. (hemoplasmas), which may cause economic losses and reduced productivity. Two common bovine hemoplasma species, Mycoplasma wenyonii ( Mw ) and “ Candidatus Mycoplasma haematobovis” corrig. (formerly “ Candidatus Mycoplasma haemobos”; C Mhb), have been reported worldwide. However, although several putative species have been hypothesized to circulate in cattle or buffaloes, comprehensive genetic analyses of Mw and C Mhb from Thailand remain limited. Methods In this study, we investigated the molecular occurrence and genetic diversity of bovine hemoplasmas in 522 dairy cattle from Thailand using 16S and 23S rRNA genes. A total of 522 blood samples were screened for hemoplasma infection using a PCR targeting the 16S rRNA gene. A non-random subset of 52 of the 161 PCR-positive samples, selected primarily on the basis of strong and discrete PCR bands, was successfully sequenced for both the 16S and 23S rRNA genes. Results PCR detected hemoplasmas in 30.8% (161/522; 95% CI 26.9%–35.0%) of cattle. Of 161 positive samples, 52 were successfully sequenced for both 16S and 23S rRNA genes. Among the 52 non-randomly selected samples, phylogenetic analyses identified sequences assigned to two recognized bovine hemoplasma taxa and two additional divergent lineages within the Mw complex. These lineages are provisionally regarded as candidate lineages pending genomic and biological characterization. Conclusions This study demonstrates underrecognized genetic diversity within the Mw complex in Thai dairy cattle. The divergent lineages were identified based on analyses of partial 16S and 23S rRNA gene sequences. Confirmation of their taxonomic status will require whole-genome sequencing, additional independent genetic markers, and biological characterization, including investigation of their pathogenicity and transmission.