A study of the environmental survival of Mycobacterium bovis on a farm in New Zealand

Mycobacterium bovis organisms absorbed on cotton ribbons were placed in different natural habitats on a farm in New Zealand. Mycobacterium bovis was not re-isolated from ribbons placed on pasture after 4 days, Survival on ribbons was longest in brushtail possum dens, where the maximum period of survival in dens was less than 7 days in summer and greater than 14 days but less than 28 days in winter and spring. The maximum period of survival on a forest floor was intermediate between pasture and dens - less than 4 days in summer and greater than 14 days but less than 28 days in winter. The overall probability of survival was influenced by season and was shortest in summer and longest in spring and winter. Survival time increased as minimum daily temperatures decreased. These studies showed there was a relatively short period of survival of M. bovic outside hosts and support a conclusion that environmental contamination of pasture, particularly in summer months, may be relatively unimportant in the epidemiology of tuberculosis in cattle, deer and possums.