In Spain, even though paratuberculosis vaccination in sheep and goats has been allowed and even recommended, its use in cattle has been opposed by the animal health authorities because of its potential interference with the diagnosis of tuberculosis. The increased incidence of this disease in dairy herds in a moment in which they are greatly improving their productive efficiency in other aspects, as well as the nearly complete eradication of TB has led the local Animal Health authorities in the Basque Country to endorse a field trial designed by NEIKER and supported by a national research grant and the manufacturer of the Spanish paratuberculosis vaccine, CZV. This study required a strict follow-up agreement with the farmers and began in 2003 in one single farm. Later 5 more farms have joined the trial and here we report the preliminary results of paratuberculosis vaccination on some of the most relevant aspects regarding farmer acceptance, TB diagnosis interference and other adverse effect, milk production, and culling/replacement rate effects.

Vaccination was applied to all animals present in the farm at the moment of joining the trial, and then to all heifer calves intended for replacement during their first month of life. A clinical follow-up was performed at one month post-vaccination at the beginning, and then blood and faecal samples were taken on a yearly schedule. All cullings were reported, and sample from the ones slaughtered within the Basque Country were taken for pathology and bacteriology. Records from the breeders association regarding milking monthly controls, total lactation and days of lactation were obtained and analyzed comparing pre-and post-vaccination data.

No relevant clinical effects were observed apart from the formation of a small nodule at the point of inoculation that tended to disappear or at least decrease after a few months. Comparative tuberculin testing one year and more after vaccination did not yield any positive results for bovine TB. Up to now, clinical cases have been reduced from all farms, 152 animals older than 24 months have been culled or fallen stock since the vaccination, we sampled 22,37% (34/152) of them and clinical paratuberculosis was diagnosed only in a Holstein cow and in 4 Jersey cows, that is 14,7% (5/34). We have to take into account that the Jersey breed is more susceptible and the hygiene practices of this farm were deficient. The most clear effect has been on culling rate reduction of first calving cows which was 45,82% according to milking records. Regarding the rate of excretion a reduction of 10,87% of positives by PCR was observed 12 months post-vaccination. Nevertheless, no general reduction was observed by faecal culture, but the 18,75% of the whole positive animals detected in the first sampling were heavy shedders, which disappeared 12 months after vaccination. Milk production was increased by an average 709 kg per cow after vaccination, but varied greatly according to number of lactation and farm. Given the trial design it cannot solely attributed to paratuberculosis control achieved with the vaccine. In summary, vaccination in commercial farms has brought back to normal figures the replacement rate and has probably increased the overall milk production per cow without relevant adverse effects both in clinical and TB-diagnostic terms.