Submitted to: International Society for Veterinary Epidemiology and Economics
Publication Type: Proceedings
Publication Acceptance Date: 8/5/2000
Publication Date: N/A
Technical Abstract: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time, the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced production by these animals through reduced milk production, they also present a potential infective threat to the rest of the herd. Johne's disease is difficult to diagnose and, therefore, to control. Development of accurate and sensitive diagnostic tests is dependent upon understanding how the host animal handles the infection and at what age do signs of infection, such as fecal shedding, become obvious. This study examines the fecal shedding of M. paratuberculosis blocked out by age of animal in a herd of dairy cattle with greater than 20% infection level. Results show that as the age of the animal increased, the percentage of animals actively shedding the organism in their feces increased.