Environmental Contamination on Dairy Farms with Cattle Infected with Mycobacterium Paratuberculosis

Abstract

The extent and persistence of Mycobacterium paratuberculosis environmental contamination on farms with a known history of Johne's disease is a commonly asked question by the agricultural community. Prospective buyers of farms following a dispersal sale often inquire about the possibility of newly acquired cattle becoming infected with M. paratuberculosis from the environment where Johne's cattle had previously been located. Thus, based on continuing inquiries from cattlemen, we developed a prospective research proposal to assess the extent of environmental contamination with M. paratuberculosis associated with known levels of infection in the herds as determined with whole herd fecal culture tests of adult cattle using a sensitive technique utilizing centrifugation¹.

Previous studies on the survival of M. paratuberculosis have been largely conducted under standardized laboratory conditions and not from samples taken from the immediate farm environment^2,3,4. Those studies suggested that M. paratuberculosis is somewhat long lived in a variety of environmental conditions. Non-laboratory based studies have focused on the survival of M. paratuberculosis in slurry and no studies have focused on the extent of soil and environmental contamination on farms with Johne's disease.

The frequency of occurrence of M. paratuberculosis in the environment of farms with known infection of cattle with M. paratuberculosis has not been reported. But, the survival of M. paratuberculosis in water, slurry, urine and other media has been published^2,3,4,5. Previous authors often used laboratory-grown isolates then inoculated a variety of materials and monitored the recovery rate over time. Vishnewskii⁶ first reported that bovine urine markedly reduced the survival time of M. paratuberculosis to less than 10 days. The inhibitory effect of urine on tubercle bacteria growth has also been recognized for some time but the factor responsible for the inhibition has not been isolated^7,8. Urine has a similar inhibitory effect on salmonella⁹.