The effects of control measures for paratuberculosis on sero-prevalence and clinical disease in Northern Italian dairy herds

The effects of a control program for paratuberculosis were assessed during a six years period (2001-2006). The survey involved 8 dairy herds located in Northern Italy, with a number of animals aged >24 months ranging from 224 to 784, mean 437 (SD = 154), median 411. Globally, a mean of 3,497 (SD = 328) animals aged >24 months per year were monitored during the six years period. Cows showing diarrhoea were readily detected, isolated and culled after laboratory confirmation. Cows were tested by an indirect blood serum ELISA during the dry period. Calves were fed only with colostrum from sero-negative cows and with milk submitted to thermic treatment (70°C for 40 min). Based on the total number of animals > 24months of age, historical means (from 1995 to 2000) of the sero-prevalence and prevalence of clinical cases were 12.6% and 5.5%, respectively. Statistical analysis of sero-positivity and clinical cases trends after the beginning of the control program showed a significant (p<0.01) reduction of both parameters during the six years period. In particular, the sero-prevalence decreased from 12.7% to 7.3% and clinical cases decreased from 5.3% to 3.2%. Following the use of the pasteurizers, a strong reduction of neonatal diarrhoea was observed in all the herds. In addition, the calf’s mean weight gain/day moved from 500 g to 900 g. Conversely, an increase of myodystrophy cases was detected after two months of age. The problem was solved by adding selenium and vitamin E to the pasteurized milk.