Goat
paratuberculosis is a chronic disease caused by Mycobacterium avium
subsp. paratuberculosis(MAP), characterized by enteritis,
progressive loss of body weight, and decrease in production,
especially in dairy goats. The disease is worldwide distributed and
in Chile the prevalence is suspected to be high in dairy herds with
intensive management systems and specialized breeds for milk
production. There is no single test able to detect all infected
animals and the faecal culture and the ELISA test are the most
widely used tests to diagnose the disease. However, faecal culture
is laborious, expensive and takes a long time to give a result and,
therefore, the ELISA test, despite its low sensitivity, is the best
alternative to be used as a diagnostic tool in Chilean dairy goat
herds. The main objective of this study was to evaluate the
sensitivity and specificity of four commercial bovine-ELISA kits
for the diagnosis of paratuberculosis in dairy goats. A total of
379 serum samples from dairy goats >2 years old with known
infection status belonging to the bank of sera of the
Paratuberculosis Laboratory, Microbiology Department, Universidad
Austral de Chile, were analyzed. All sera were previously collected
from animals in four infected and four non-infected dairy goat
herds from different regions of the country. Serum samples were
simultaneously assayed for anti-MAP antibody using four different commercial bovine-ELISA kits
(A, B, C, and D), and performed after manufacturers'
recommendations. Sensitivity and specificity of each test were
calculated by means of 2x2 tables and for comparison between tests
the Z test was used. Association and agreement between two kits
were determined by means of the McNemar Chi square and the Kappa
tests, respectively. Positive results were obtained in 49 (12,9%)
samples assayed with kits A, 33 (8,7 %) for kit B, 46 (12,1 %) for
kit C, and 42 (11,1 %) for kit D. Test sensitivity varied between
69,4% (B) and 77,7% (A, C, and D). Test specificity was 100% for
all four kits. The McNemar P value showed statistic differences
between kits A and B, B and C, and B and D but no difference
between kits A, C, and D. The highest kappa value was 0,806 for kits A and D, a high agreement between
these two kits. These results suggest that ELISA test developed for
diagnosis of paratuberculosis in cattle can be equally used for
diagnosis in goats though differences in sensitivity and
specificity exist between kits, in particular when applied to low
shedder animals, being kit D, the only licensed ELISA kit for
goats, the most accurate test for detecting low shedder animals.
Consequently, the ELISA test can be recommended for the diagnosis
of paratuberculosis in dairy goat herds as a more inexpensive and
confident alternative diagnostic test.