European hares in Chile: a different lagomorph reservoir for Mycobacterium avium subsp. paratuberculosis?

Ruminants are the principal host for infection by Mycobacterium avium subsp. paratuberculosis (Map), the cause of Johne's disease. Based on studies of a Map-infected population of European rabbits (Oryctolagus cuniculus) in Scotland, lagomorphs as a broad taxonomic order were proposed as potential nonruminant reservoirs for Map. To determine whether a different lagomorph species may serve as a wildlife reservoir, we investigated Map infection in European hares (Lepus europaeus) sharing habitat with known Map-infected dairy cattle in southern Chile. Fecal, mesenteric lymph node, and ileal samples were aseptically collected from 385 wild hares for liquid culture and real-time polymerase chain reaction identification of acid-fast isolates. All tissue samples were also acid-fast stained and examined microscopically. We isolated Map from at least one tissue from 48 hares (12.6%) and fecal samples from 16 hares (4.2%). No Map was found in tissues of eight of the fecal-culture-positive hares. Histologically, all tissues from all hares were within normal limits, and no acid-fast organisms were observed in any sample. Active infection, implying amplification of the organism secondary to resultant disease, was not evident. With this report Map isolations on a population versus incidental detection have now been made from two lagomorph species. However, although the rabbit population studied in Scotland appears to function as a Map reservoir, the hares studied in Chile appear to be a dead-end host, serving only as potential mechanical vectors for the organism.

Evaluation of four commercial enzyme-linked immunosorbent assays for the diagnosis of bovine paratuberculosis in Chilean dairy herds.

The accuracy of 4 commercial enzyme-linked immunosorbent assays (ELISAs) for diagnosis of bovine paratuberculosis was compared using sera from 53 Mycobacterium avium subsp. paratuberculosis (MAP) fecal culture-positive dairy cows (cases) and sera from 345 dairy cattle resident in 11 fecal culture-negative herds on 2 consecutive occasions 1 year apart (controls). The specificity of all 4 ELISA kits was >99%, and their diagnostic sensitivity ranged from 30.2% to 41.5%. Pairwise comparison of ELISAs found no significant differences (McNemar's chi-square test > 0.05), and assay agreement for categorical assay interpretation (positive or negative) was high (>98%) with kappa values ranging from 0.84 to 0.95. Receiver operating characteristic (ROC) curve analysis and the corresponding area under the ROC curves indicate that kit B had the highest overall accuracy. Thus, all 4 ELISA kits for bovine paratuberculosis had comparable accuracy when tested on Chilean dairy cattle, with kit B having a slight statistical advantage based on ROC area under the curve analysis. This suggests that any of the 4 kits could be appropriate for herd certification and for paratuberculosis control programs on Chilean dairy cattle.

Diagnosis of paratuberculosis by fecal culture and ELISA on milk and serum samples in two types of Chilean dairy goat herds.

Fecal culture has been the primary method used to diagnose paratuberculosis in goats. It is laborious, slow, and expensive. Validation of enzyme-linked immunosorbent assays (ELISAs) on milk samples could make paratuberculosis testing more widely available for goat farmers. The aim of this study was to determine the accuracy of serum and milk ELISAs for paratuberculosis, relative to fecal culture, in Chilean dairy goats. Eight dairy goat herds were selected. Feces, blood, and milk samples were collected from all female goats >2 years old. Fecal samples were cultured using Herrold egg yolk medium with mycobactin J and antibiotics. Serum and milk samples were tested using a commercial ELISA kit for Mycobacterium avium subsp. paratuberculosis antibody detection. A total of 383 goats were tested by ELISA and fecal culture. The sensitivity of ELISA on serum and milk relative to fecal culture was 74.3% (95% CI: 59.8-88.8) and 60% (95% CI: 43.8-76.2), respectively. The corresponding values for ELISA specificity based on the percentage of non- M. avium subsp. paratuberculosis-infected goats testing ELISA-negative were 98.6% (95% CI: 96.6-100) and 99.3% (95% CI: 97.9-100) on serum and milk, respectively. Proportions of positive results for serum and fecal samples were significantly different, whereas the proportions of positive results for milk and fecal samples were not significantly different. The milk ELISA had a moderate level of agreement with fecal culture results (Kappa = 0.57). The paratuberculosis ELISA on goat milk samples may be a cost-effective, accurate alternative to fecal culture.

Goat paratuberculosis in Chile: first isolation and confirmation of Mycobacterium avium subspecies paratuberculosis infection in a dairy goat.

In October 2004, 41 goats > 2 years old from a Saanen dairy goat herd located in Purranque County, 10th Region, Chile, were sampled and tested for paratuberculosis. While collecting samples it was observed that several goats were thin and emaciated. One goat was sufficiently debilitated to warrant humane euthanasia. This animal was brought to the Veterinary School at the Universidad Austral de Chile for necropsy. The goat selected for necropsy was a 12-year-old doe. The animal showed classical clinical signs of caprine paratuberculosis: emaciation despite willingness to eat, dry and rough hair coat, and no evidence of diarrhea. Gross pathology and histopathology of the necropsied goat were consistent with paucibacillary paratuberculosis. Bacteriology, serology, and PCR confirmed the diagnosis. This is the first published report of goat paratuberculosis in Chile confirming a case of caprine paucibacillary paratuberculosis.