Effect of vaccination against Mycoplasma hyopneumoniae of breeding pigs pre-farrowing on colonization rates of piglets at weaning

Mycoplasma hyopneumoniae is one of the primary pathogens involved in the Porcine Respiratory Disease Complex. Breeding sows are responsible for maintaining M. hyopneumoniae infections within the herd and young sows are more likely to transmit the pathogen to their piglets compared to older sows. Additionally, piglet colonization at weaning has been suggested as a predictor of clinical disease and lung lesions at slaughter. The aim of this study was to investigate whether vaccination of sows against M. hyopneumoniae at the end of gestation can reduce the colonization rate of piglets at weaning.

Two farrow-to-finish herds were selected; herd A (400 sows) and herd B (600 sows). From 6 consecutive farrowing groups of sows in each herd, 3 groups were vaccinated against M. hyopneumoniae and 3 remained non-vaccinated. Vaccination of the groups was applied in an alternating way. In vaccinated groups, all gilts and sows received twice a commercial bacterin (Ingelvac MycoFLEX®) at 6 and 3 weeks before the expected farrowing date. Then, from each vaccinated or non-vaccinated group of sows within each herd, 5 primiparous sows together with their litters were selected. Laryngeal swabs were collected from each primiparous sow within 24 hours after parturition, and additionally at the day of weaning from all piglets belonging to the selected primiparous sows. Collected swabs were tested for the presence of M. hyopneumoniae using a nested PCR. The vaccinated groups were compared with the non-vaccinated ones using logistic regression.

In herd A, 10% of each of the vaccinated and non-vaccinated primiparous sows were positive for M. hyopneumoniae (P=0.998). In this herd, 0.86% and 1.60% of the piglets born from the vaccinated and non-vaccinated primiparous sows, respectively, were positive for M. hyopneumoniae at weaning (P=0.584). In herd B, 0% of the vaccinated and 20% of the non-vaccinated primiparous sows were positive for M. hyopneumoniae (P=0.598). In this herd, 1.06% and 3.12% of the piglets born from the vaccinated and non-vaccinated primiparous sows, respectively, were positive for M. hyopneumoniae at weaning (P=0.176). The risk for the piglets of the non-vaccinated primiparous sows to be positive for M. hyopneumoniae in herd A was 1.96, while in herd B was 2.95 times higher when compared to that of the piglets of the vaccinated primiparous sows.

In both herds, piglets originating from the vaccinated primiparous sows had 2 to 3 times lower risk of being colonized with M. hyopneumoniae at weaning. More litters will have to be investigated, since statistics were not able to demonstrate a clear benefit, likely due to the low number of colonized piglets.

Disclosure of Interest: None Declared.