Significant reduction in bacterial shedding and improvement in milk production in dairy farms after the use of a new inactivated paratuberculosis vaccine in a field trial

Abstract

Background: Paratuberculosis vaccination has been in use in some regions for many decades, but results have not been widely spread. A new Mycobacterium avium subsp. paratuberculosis (MAP) killed vaccine was studied in relationship with its effects on fecal shedding and milk production in four farms while other two were kept as controls submitted to a test and cull scheme.

Findings: Fecal detection (n = 1829) and milking records (n = 2413) have been analyzed after two (5 herds) and four (1 herd) years of the beginning of the intervention. Shedder prevalence was reduced by 100% in three of the four vaccinated farms, 68% in the total of vaccinated animals and 46% in the two control farms. Total amount of MAP shed was reduced 77% in the vaccinated farms and 94% in the control farms. Overall milk production increased up to 3.9% after vaccination, while there was no significant difference in production after intervention in the non-vaccinated farms.

Conclusion: MAP shedding reduction can be quickly accomplished both by vaccination and by testing and culling. However, vaccination appears to be a less expensive and more sustainable strategy since it required one single intervention and was also associated with an increase in milk production.

Figure 1

Prevalence of cows excreting MAP in their feces at each fecal control as measured by isolation and by IS900 PCR. AI0: Before intervention, PI1: First post-intervention control; PI2: Second control post-intervention. Culture T&C: Results of fecal culture in the two herds without vaccination. Culture VAC: Results of fecal culture in the four herds with vaccination. PCR T&C: Fecal IS900 PCR positive results in the two herds without vaccination. PCR VAC: Fecal IS900 PCR positive results in the four herds with vaccination.

Figure 2

Evolution of estimated amount of daily bacterial shedding per cow according to the strategy. Although in the first years T&C appears to be substantially more efficient, vaccination still seems to reduce shedding by three fourths. AI0: before intervention, PI1: First post-intervention control; PI2: Second control post-intervention; Reduction: Percent of reduction in the estimated amount of bacteria shed from the initial to the last control. Notice that this approach shows a slower reduction with vaccination than when only frequency of shedders is considered.