Prevalence and regional distribution of paratuberculosis in dairy herds inthe Netherlands

In the Netherlands a survey was conducted to estimate the prevalence of par atuberculosis in dairy herds. In total 15822 cows of at least 3 years of ag e, belonging to 378 herds were tested using an absorbed ELISA. Of these her ds, 55% (n = 207) had one or more serologically positive cows. Of the posit ive non-vaccinated herds, most had one (n = 98) or two (n = 49) positive co ws. The percentage positive cows per herd was 2.5 +/- 3.2%. The true prevalences on cow and herd levels, based on a test sensitivity th at ranged from 0.3 to 0.4 and a specificity that ranged from 0.985 and 0.99 5, were estimated at 2.7-6.9% and 31-71%. Seven herds had been vaccinated a gainst paratuberculosis and these herds had a significantly higher percenta ge of serologically positive cows (23%) than the non-vaccinated herds (2.5% ). In conclusion, a small percentage of the dairy cows and a high percentage o f the dairy herds in the Netherlands is serologically positive. The percent ages true infected cows and herds are difficult to estimate precisely due t o uncertainties in test sensitivity and specificity. (C) 2000 Elsevier Scie nce B.V. All rights reserved.