Survival of Mycobacterium avium subsp paratuberculosis in amitraz cattle dip fluid

Objective To determine the survival time of Mycobacterium avium subsp parat uberculosis in amitraz-based cattle dip fluid derived from an active dip si te in northern New South Wales. Procedure Following inoculation of triplicate 5 L containers with faeces (0 .5 g/L) from a clinical case of bovine paratuberculosis, samples collected up to 8 weeks after inoculation were examined by conventional and radiometr ic culture. M a paratuberculosis colonies were enumerated on solid media. Results and conclusions M a paratuberculosis survived in amitraz cattle dip fluid for up to 2 weeks, but not 3 weeks. Where 1% of solids in dip fluid is derived from a clinical case of paratuberculosis, dip fluid may contain viable M a paratuberculosis for at least 2 weeks. These findings have impli cations for the management of cattle dip sites.