Risk factors for Johne's disease in Irish dairy herds: A case-control study

This paper reports a case control study of herd and management factors associated with the introduction and transmission of paratuberculosis into dairy herds in Ireland. Data were gathered by telephone interview. Case herds were selected on the basis of having one or more positive faecal cultures for Mycobacterium avium subsp paratuberculosis (MAP). Control herds were selected on the basis of being seronegative for MAP in a national serosurvey. Control herds were matched to case herds on the basis of the year of diagnosis of MAP in the case herds. Factors relating to disease history, herd size, neonatal feeding and management and grassland management were found to be significant (p<0.05) in the univariate analysis. The multivariate analysis found the feeding of waste milk prior to diagnosis, the absence of individual calving pens, the herd size, and herd depopulation for a notifiable disease to be significant risk factors for the occurrence of paratuberculosis. Potential feed contamination prior to the reference year, and the length of time the newborn calf spent with its dam were considered to be protective against the occurrence of paratuberculosis. With the increased global demand for dairy products, many Irish dairy herds will be undergoing expansion. Such herdowners need to be aware of paratuberculosis and take precautions to avoid its introduction and spread. Herdowners that are not unaware of their infection status need to establish it. Where disease is present management practices must be put in place to control and eradicate it.