Efficacy of a new vaccine (Myco-Suivax®) against Mycoplasma hyopneumoniae under field conditions

Swine enzootic pneumonia is caused by a complex interaction between Mycoplasma hyopneumoniae (Mh), the primary infectious agent, environmental factors, and other infectious agents. In the last few years, the efficacy of numerous vaccines has been demonstrated in reducing losses deriving from enzootic pneumonia. The objective of the present study was to evaluate the field efficacy of a new vaccine (Myco-Suivax®, Fatro) administered at a single or double dose in the presence of disease, in an Italian farrow-to-finishing farm, where the long fattening cycle causes slaughter of swine at 160–170 kg of live body weight (LBW) and 9–10 months of age. The experimental trial was conducted in a farrow-tofinishing farm of 730 sows situated in Northern Italy, where problems of enzootic pneumonia had been identified in growing pigs. Three consecutive homogeneous groups of 300 piglets each were included in the study; these were assigned at random to one of the following treatment groups: - Group A (double shot): vaccinated twice at 7 days of age and at weaning (25 days of age) at a dose of 1 ml; - Group B (one shot): vaccinated once at a dose of 2 ml on the day of the end of the weaning period (60 days of age); - Group C: control (no Mh vaccination). The efficacy of the vaccine was based primarily on the pulmonary lesions associated with respiratory disease, using the method described by Madec and Kobisch. The overall weights at the end of weaning and at slaughter were also recorded, together with feed consumption in the interval between end of weaning and slaughter, to calculate Average Daily Weight Gains (ADWG) and Feed Conversion Rate (FCR). Slaughter was performed, for pig movement restriction reasons (outbreaks of MVS in the Lombardia region in 2006-2007), between 10 and 11 months of age. The animals which died during the trial were subjected to necroscopic examination and laboratory investigations (PCR) to highlight the presence of Mh. All statistical analyses were performed using the software SPSS 12.0.0 (SPSS, 2003). Necroscopic findings and laboratory investigations highlighted the presence of M. hyopneumoniae in swine of all the treatment groups. Myco-Suivax® was able to reduce pulmonary lesions, decrease the number of animals which died and improve weight gain and the FCR in both groups subjected to vaccination. The results appear particularly significant taking into account the late slaughter age (160–170 kg of LBW) and 9–10 months of age), in which pulmonary lesions due to M. hyopneumoniae have mainly regressed and where growth tends to at slow down. In the specific field situation in which the trial was conducted, the one shot vaccination, performed at 60 days of age, was the one able to supply the best zootechnical results.