‍Project background

Paratuberculosis, also known as Johne's disease, is a chronic bacterial infection that affects the small intestine of dairy cows. The bacteria responsible for the disease, Mycobacterium avium subspecies paratuberculosis, can cause weight loss, diarrhea, and decreased milk production in infected cows. The disease is difficult to detect in its early stages and can spread rapidly through contaminated feces and milk. A few dozen cases are registered annually in Switzerland, but the current prevalence and major risk factors for Swiss dairy herds remain unknown.

This project aimed to perform a representative serological studyto assess prevalence of antibodies against paratuberculosis in Swiss dairycows. In addition, risk factors for the introduction of paratuberculosis intoherds and spread within herds were assessed through a questionnaire.

Our work

This project was implemented under the lead of the Clinic for Ruminants of the Vetsuisse-Faculty of the University of Bern. SAFOSO provided epidemiological and statistical expertise for the calculation of the sample size, assessment of the true prevalence and performed the risk factors analysis.

Results

The study involved 10,063 serum samples collected from cows over12 months of age across 171 dairy farms in Switzerland. Using a commercial ELISA test, we determined a between-herd seroprevalence of 3.6% (95%CI,0.96-8.4%). While the within-herd seroprevalence ranged from 2.3% to 5.5%,the median was 3.6% in the nine farms testing positive for MAP.

We also identified several risk factors associated withseropositive herds. Larger herd sizes and the common grazing of lactating cowswith cows from other herds were associated with a higher likelihood ofseropositive status. Conversely, heifers sharing alpine pastures with dairycattle from other herds were associated with a reduced probability of the herdtesting seropositive.

Despite these findings, reliable identification of significantrisk factors for MAP spread within herds proved challenging due to lowseroprevalence and the limited sensitivity of the ELISA test, particularly insmall herds.

For more insight access the publication here: Link