Investigating Mycoplasma wenyonii and Candidatus Mycoplasma haematobovis coinfection patterns in cattle from southwestern France reveals strain-specific traits

Hemotropic mycoplasmas (hemoplasmas) infecting cattle were first detected in France in 2019 during a clinical outbreak, but their prevalence both at the species and strain levels remains unknown. This study therefore aimed to determine the prevalence of hemoplasmas and their coinfections, and to assess the within and between herd diversity in five fully sampled dairy herds. Detection was performed using 16S rRNA quantitative polymerase chain reaction (qPCR), as well as three strain-specific rnpB qPCR assays targeting Candidatus Mycoplasma haematobovis (CMh, formerly Ca. M. haemobos), Mycoplasma wenyonii strain Mexico (Mex), and Mycoplasma wenyonii strain Massachusetts (Mass). A total of 1011 cattle were sampled, of which 88.7% (897/1011) tested positive by 16S rRNA qPCR. Detection rates for CMh, Mex, and Mass were 67.7% (684/1011), 65.9% (666/1011), and 19.8% (200/1011), respectively. Concordance between 16S rRNA qPCR and strain-specific rnpB qPCR was 92% (931/1011). Coinfections were detected in 67.8% (565/833) of 16S PCR-positive animals, with the CMh + Mex combination being the most frequent. The Mass strain was predominantly found in association with the two other hemoplasmas. For all four PCR assays, hemoplasma positivity was significantly associated with both herd and animal age in the five fully sampled dairy herds. Further studies are needed to elucidate transmission routes and pathogenicity mechanisms of hemoplasmas.