AUTHOR=Valeris-Chacin Robert , Powledge Sherri , McAtee Taylor , Morley Paul S. , Richeson John 

TITLE=Mycoplasma bovis is associated with Mannheimia haemolytica during acute bovine respiratory disease in feedlot cattle

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.946792

DOI=10.3389/fmicb.2022.946792

ISSN=1664-302X

ABSTRACT=<p>Bovine Respiratory Disease (BRD) represents a significant burden to the health of feedlot cattle and the profitability of the beef industry in the US. <italic>Mannheimia haemolytica</italic> is widely regarded as the primary bacterial pathogen driving acute BRD. While <italic>Mycoplasma bovis</italic> is most commonly implicated in chronic cases of BRD, this agent's potential role in acute stages of BRD is unclear. Therefore, this study aimed to evaluate potential associations between <italic>M. bovis</italic> and <italic>M. haemolytica</italic> during acute BRD in feedlot cattle. Nasal swabs (<italic>n</italic> = 1,044) were collected over time from feedlot cattle (<italic>n</italic> = 270) enrolled in an experiment assessing the effect of vaccination for Bovine Respiratory Syncytial Virus (BRSV). Swabs were analyzed for detection of <italic>M. bovis, M. haemolytica, Pasteurella multocida, Histophilus somni</italic>, and BRSV <italic>via</italic> multiplex qPCR assays. Data were analyzed using inverse conditional probability weighted (ICPW) logistic regression models to investigate potential effects of <italic>M. bovis</italic> presence on arrival (d0), day seven (d7) and day 14 (d14) post-arrival on <italic>M. haemolytica</italic> prevalence on day 28 (d28) post-arrival, adjusting for the previous history of <italic>P. multocida, H. somni</italic>, BRSV, BRD morbidity, and body weight. The potential association between time-to-BRD detection and <italic>M. bovis</italic> presence on d0, d7, and d14 post-arrival, was inferred <italic>via</italic> an ICPW time-to-event model. The presence of <italic>M. bovis</italic> in nasal swabs collected on d7 post-arrival was significantly associated with an increase in the prevalence of <italic>M. haemolytica</italic> on d28 (prevalence difference: 45%; 95% Confidence Interval: 31%, 60%; <italic>P</italic>-value &lt; 0.001). Significant time-varying coefficients for <italic>M. bovis</italic> presence were detected at d0, d7, and d14 post-arrival in the ICPW time-to-event model (<italic>P</italic>-value &lt; 0.001). The shortest median time-to-BRD detection was 29 days in cattle that were <italic>M. bovis</italic> positive on d0, d7, and d14 post-arrival and in those that were positive on d0 and d14 post-arrival. Under the conditions of this study, our findings suggest that <italic>M. bovis</italic> may be influencing the respiratory environment during the acute phase of BRD, increasing the abundance of <italic>M. haemolytica</italic>, which could have important impacts on the occurrence of BRD.</p>