Efficacy of Mycoplasma hyopneumoniae vaccination at or shortly before weaning under field conditions

The aim of this study was to investigate the efficacy of a one-shot vaccination applied either at weaning or 3 days before weaning in a herd infected with M. hyopneumoniae (Mhyo) and other respiratory pathogens.

 

At 14 days of age, 828 piglets were randomly divided into 3 groups of 276 piglets each: 2 groups were vaccinated with Ingelvac MycoFLEX® either 3 days before weaning (V1) or at weaning (21 days of age, V2); a third group was left non-vaccinated (NV). After the nursery period 304 pigs were allocated to fattening unit 1 (F1) and 500 pigs to fattening unit 2 (F2). 

Pigs from the 3 treatment groups were equally allocated across F1 and F2. Diagnostic investigation included necropsies of dead pigs, serology against Mhyo and other respiratory pathogens, and quantitative real-time (qPCR) for the detection of Mhyo DNA on tracheobronchial swabs at 10, 14 and 18 weeks of age (same 20 pigs/group). Average daily weight gain (ADG), respiratory disease score (RDS), mortality rates and pneumonia lesions at slaughter (27 weeks of age) were assessed.

 

 

Necropsies and serology showed the presence of secondary bacteria (Trueperella pyogenes, Pasteurella multocida and Streptococcus suis), and also chronic infection with porcine reproductive and respiratory syndrome virus and porcine circovirus type 2. Overall, 50/60 pigs were seropositive for Mhyo one week prior to slaughter and 18/60 of those pigs were positive by qPCR at 18 weeks of age. Additionally, in F1 an outbreak of swine influenza H3N2 was confirmed at 20 weeks of age. Statistically significant differences were obtained in F2 where group V1 had higher weight gains and ADG compared to groups V2 and NV (P<0.05). When taking into account both fattening units, the ADG for the entire period in groups V1, V2 and NV were 610, 600 and 593 g, respectively (P=0.164) and group V1 was the only group where coughing severity did not increase significantly between the initial stage (10 to 20 weeks of age) and the end of the fattening period (20 to 26 weeks of age) (P>0.05). Regarding the mortality rates and lung lesions at slaughter, and also the weight gains and ADG in F1, differences between group V1 and groups V2 and NV were statistically non-significant.

 

In conclusion, vaccination against Mhyo ahead of weaning provided significantly better performance in F2. When taking both fattening units, performance of both vaccinated groups was numerically better but did not reach statistical significance. It can be assumed that especially the influenza outbreak in F1 and the fact that both F1 and F2 were facing mixed respiratory infections have influenced the performance of both vaccinated groups across all measured parameters.

Keywords: Weaning; Mycoplasma hyopneumoniae; Vaccination.