Short communication: Herd-level prevalence of Mycobacterium avium ssp. paratuberculosis is not associated with participation in a voluntary Alberta Johne's disease control program

Johne's disease (JD) control programs for dairy farms have the general objective of reducing both cow- and herd-level prevalence of Mycobacterium avium ssp. paratuberculosis (MAP). An important aspect of many programs is herd testing for MAP to determine the infection status of participating farms. However, it is uncertain whether MAP herd-level prevalence on farms voluntarily participating in a JD control program is different from that on nonparticipating farms. Therefore, the aim was to compare MAP infection status of participants and nonparticipants in the Alberta Johne's Disease Initiative (AJDI), a voluntary JD control program initiated in 2010 in Alberta, Canada. Between September 2012 and August 2013, environmental fecal samples were collected from 93 randomly selected farms not enrolled in the AJDI. Additionally, 81 farms that initially enrolled in the AJDI during the same time interval were also sampled. Samples were collected from 6 defined locations on each farm and cultured for MAP. Results were confirmed using conventional IS900 PCR and F 0285 quantitative PCR. Overall, 51% of participating and 51% of nonparticipating farms were identified as being MAP-infected. Furthermore, based on multivariable logistic regression, the number of MAP-positive samples was not associated with AJDI participation (taking herd size into account as a potentially modifying or confounding variable). In conclusion, there was no indication that voluntary participation in the AJDI was associated with herd-level MAP prevalence.