Johne's Disease

Seroprevalence of Mycobacterium avium subsp. paratuberculosis in Florida Beef and Dairy Cattle

Abstract

Mycobacterium avium subspecies paratuberculosis (MAP) is an acid fast intracellular bacillus that infects ruminants worldwide. The disease is characterized by chronic diarrhea and weight loss, despite a good appetite, even on a high plane of nutrition. The disease has a significant economic impact on both the dairy and beef cattle industry in the USA. Control of the disease is difficult due to fecal shedding of the sub-clinical animal and much effort has been put into identifying the disease in the early stages. Currently there are no reliable tests for detecting early infection. The ELISA test has been used in many seroprevalence studies. This method offers the advantage of availability of results in a short period of time and comparable sensitivity to the fecal culture. Sensitivity of the test is approximately 40-50%, but may vary from 15-87% depending on the animal's stage of the infection. Higher sensitivities are obtained from heavy shedders of the bacteria. The specificity of the current ELISA test is 99%. In 1990 Braun et al reported ELISA results of a 1986-1987 survey of Florida cattle indicating a prevalence of 8.6% in beef cattle and 17.1 % in dairy cattle. The high prevalence in that study warranted the re-evaluation of the prevalence of Johne's disease in the state. The objective of this study was to estimate the apparent prevalence of MAP antibodies in Florida cattle from samples submitted to the Florida State Veterinary Diagnostic Laboratory.