Abstract:
A study was performed in Umbria, central Italy, to find out whether different culling strategies
adopted by farms to control Johne’s disease (JD) infection exerted effects on the seroprevalence
in dairy cattle. Fifty Fresian dairy herds in the Perugia and Assisi districts were visited and an audit
of herd management was conducted. Among the 50 herds, 20 were selected for the consistency of
management practices and, according to the culling strategy, two groups were created: group A
(aggressive culling protocol, with average herd productive life <1100 days) and group B (lower culling
rate, with productive life greater than 1500 days). The presence of antibodies to Mycobacterium avium
subspecies paratuberculosis (Map) in the serum was determined using a commercial enzyme-linked
immunosorbent assay (ELISA) kit. It was found that 3.3% (n = 14) of the cows of group B (n = 422,
from 17 herds) were positive for Map antibodies, in comparison with 5.7% (n = 21) of the cows from
group A (n = 366, from three herds). The odds ratio from multiple logistic regression (adjusted
odds ratio 2.446, 95% confidence interval 0.412 to 14.525) showed that Johne’s disease prevalence in
herds with a greater productive life was not higher than in herds with typical modern management
characterized by more aggressive culling. This is a significant finding, indicating that aggressive
culling may not be necessary. Current JD control recommendations are derived from data obtained in
high-prevalence paratuberculosis areas (northern Europe, including northern Italy), while methods
of information transfer to dairy farms in low-prevalence areas should be reassessed to ensure that
the correct measures, including basic calving management and calf-rearing practices, are thoroughly
implemented. Using the manufacturer’s suggested cut-off for a positive ELISA test and the sensitivity
and specificity claimed, the overall true prevalence in Umbria dairy cattle was calculated as 7% (95%
confidence interval 5.2% to 8.8%).
