A retrospective study to identify concomitant pathogens in Mycoplasma gallisepticum positive commercial turkeys and the development of a predictive model of Mycoplasma gallisepticum serologic status in California (2008–2019)

Mycoplasma gallisepticum (MG) is an economically significant pathogen of poultry which results in severe disease especially when complicated by other respiratory pathogens. The objectives of this study, were to establish preliminary baseline data on the respiratory pathogens in MG positive commercial turkey flocks in California and to identify key predictor variables of MG serologic status. The retrospective study analyzed a total of 54 flocks in which MG was confirmed in central California from 2008 to 2019 by California Animal Health and Food Safety laboratories (CAHFS). Of the 54 flocks that were confirmed positive by quantitative polymerase chain reaction (qPCR), 34 (63%) had positive MG ELISA titers and 20 (37%) were negative. Escherichia coli was the most common pathogen isolated in 13 (24.1%) flocks followed by Bordetella avium, Mycoplasma synoviae, and Ornithobacterium rhinotracheale in 10 (18.5%), 8 (14.8%), and 7 (13%), respectively. The mean age at which flocks were submitted for necropsy to the CAHFS laboratories and confirmed as MG qPCR positive was approximately 15 wk. To assess the main effects on MG serologic status, a stepwise logistic regression model was developed. Of the 6 independent variables examined (age of flock, season, farm size, company, number of concurrent pathogens and year), only age of flock (odds ratio = 1.7, P= 0.002) was determined to be a significant factor in the final model. This study provides preliminary baseline data on the concurrent infectious pathogens in qPCR MG positive commercial turkeys. It also identified potentially critical information as well as the age of detection, which may aid in the implementation of targeted control and prevention strategies.