Hemotropic mycoplasma is increasingly being recognized as an infectious agent by dairy practitioners, but little is known about this organism or its pathogenic mechanisms, raising concern about the potential effects of the infection on dairy animal health and productivity. Mycoplasma wenyonii and Candidatus Mycoplasma haemobos are parasitic bacteria that infect red blood cells of cattle. Until recently, very little was known about the prevalence of infection with these organisms in U.S. dairy cattle. Schambow et al (2021) reported a 100% herd-level apparent prevalence in adult cows tested in 82 herds located in Wisconsin and Michigan. In that study, >70% of first lactation cows were infected, which suggested that infection occurred prior the first calving (Schambow et al., 2021). The overall hypothesis of this thesis is that infection with hemoplasmas primarily occur prior to first calving, vary with age, impact some hematological values, and that transplacental transmission is uncommon. The aims of this thesis are to: 1) determine the prevalence and dynamics of infection of with M. wenyonii and C.M. haemobos infections in calves and replacement heifers on Michigan dairy farms and assess potential associations between infection status and altered hematological values; and 2) determine if infection with M. wenyonii or C. M. haemobos occurs prior to birth (vertical transmission), and to evaluate the presence of bovine hemoplasma DNA in the colostrum.
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