Identification and control of paratuberculosis in a large goat herd

SUMMARY Mycobacterium paratuberculosis infection was detected in 2 goats in 1974 and in 5 goats in 1975; 5 of which were from a single herd. The magnitude of the subsequent epizootic in the goat herd was not recognized until 1977, when results of bacteriologic culture of fecal and tissue specimens, antibody determinations (agar-gel immunodiffusion test), and histopathologic studies became available. By 1984, paratuberculosis had been diagnosed in 124 goats. Nearly all the goats were being used in antiserum production and had been given Freund complete adjuvant and human antigens. From 1974 to 1986, herd size varied from 100 to 300. The yearly incidence of paratuberculosis decreased from 13.2% (27 of 204 goats) in 1977 to 0% in 108 goats in 1985. The prevalence was higher in does. In goats that arrived on the farm in 1975 and before, 49 of 121 (40.5%) does developed paratuberculosis vs 41 of 120 (34.2%) wethers. In goats arriving on the farm in 1976 and after, 25 of 274 (8.5%) does and 9 of 216 (4.1%) wethers developed paratuberculosis. The average incubation period was approximately 4 years from arrival on the farm in every year except 1978, regardless of whether the goat was born on the farm or was purchased elsewhere. Pathologic studies revealed gross and microscopic lesions predominantly in the lower portion of the ileum and associated lymph nodes; however, in goats with advanced disease, lesions were detected in the entire intestinal tract, liver, spleen, and lungs. Amyloidosis was detected in the spleen, liver, kidneys, and/or adrenal glands of 67 of 118 (56.8%) necropsied goats with paratuberculosis and 149 of 387 (38.5%) goats without bacteriologic and/or histologic evidence of paratuberculosis. Nonrandomized therapeutic trials were conducted in 19 goats with fecal cultures considered positive for M paratuberculosis: 4 were given isoniazid; 4 were given isoniazid plus rifampin; 4 were given isoniazid plus ethambutol; and 7 were given isoniazid, rifampin, and ethambutol. All drugs were given orally each day for 3 to 16 months, but without success. Major changes were made in herd management to control the epizootic and to eradicate the disease. Using agar-gel immunodiffusion testing quarterly, bacteriologic culture of fecal specimens semiannually, and weighing all goats monthly, earlier diagnosis of paratuberculosis was achieved. Isolation or euthanasia of all goats with confirmed or suspected paratuberculosis was carried out promptly. All young and newly purchased goats were quarantined. Strict sanitation rules were followed. The herd has remained free of paratuberculosis since 1984.