Herd testing to control bovine Johne's disease

There are about 1,800 cattle herds in Victoria in which Johne's disease (JD) has been diagnosed in the last 5 years, the majority of which are dairy herds. The costs associated with JD include production losses and trade restrictions. Stud and elite breeding herds are the most financially affected. Traditional control methods rely on management practices to reduce the opportunity for calfhood infection. These include preventing calfhood contact with adult cattle, with pastures grazed by adult cattle and with effluent from dairy sheds. The absorbed ELISA blood test is able to detect up to 50% of infected cattle over 2 years of age and can be used in conjunction with management practices to improve JD control. Effective control measures however require a commitment over many years by herd owners. In 1996, the Victorian cattle industries and government established a JD test and control program under which participating farmers are provided with an annual ELISA test of the adult herd and advice on disease control that is tailored to their farm. The program is delivered through private veterinarians under contract with the government. There are over 500 herds enrolled in the program and about one third of these have had 3 or more whole herd tests. This paper provides a review of the program to date. It describes changes in ELISA reactor rates and numbers of clinical cases, and provides evidence for progress in the program.