Prevalence of Mycoplasmopsis bovis and Histophilus somni in raw bovine semen from artificial insemination collection centers in the United States.

Mycoplasmopsis bovis and Histophilus somni are important bovine bacterial pathogens. M. bovis causes mastitis and bovine respiratory disease (BRD) and is linked to reduced fertility and abortion. The H. somni is implicated in BRD, arthritis, and myocarditis. Currently, under the guidance of Certified Semen Services (CSS), semen used for artificial insemination (AI) is treated with gentamicin, tylosin, lincomycin, and spectinomycin (GTLS) during the semen extension process to control and prevent the transmission of various bacterial species, including M. bovis and H. somni. The GTLS has been shown to only exhibit a bacteriostatic effect on M. bovis, and therefore understanding the prevalence of M. bovis is of interest, especially as evidence has demonstrated that M. bovis can be spread through contaminated extended semen used for AI. This led to a nationwide survey sampling untreated, raw bovine semen from various CSS-certified AI facilities. Raw semen was tested to determine the prevalence of M. bovis and H. somni. Culture-based methods were used to evaluate semen for both organisms, and PCR was additionally used to evaluate for M. bovis. Of 278 semen samples, no M. bovis was detected using PCR or culture, leading to a ≤0.9% likelihood of M. bovis being shed into semen at CSS-approved AI facilities. However, high H. somni carriage rates (>86%) were observed. These findings indicate that facilities have limited likelihood of transmitting M. bovis in semen. The H. somni should be re-evaluated as a pathogen of interest to the AI industry, as these data indicate a high carriage rate.