- 2 minutes, 57 seconds
- Expertise article
- Valérie Normand, Josselin Metais, Franck Bouchet, Pauline Berton, Gwenaël Boulbria, Arnaud Lebret
MATERIALS AND METHODS
Selection of the farm:
This study was conducted in a 250-sow farrow-to-finish farm located in Brittany with a 7 batches management and a 21-day-weaning age. Before the start of the study, a circulation of a type 1-strain of PRRSv, Mhyo and PCV2 was confirmed in fatteners. Selection of the piglets and vaccination protocol:
In total, 1176 piglets from 4 successive batches were included around weaning. The 685 piglets of the two first batches (group A) were vaccinated on the same day, around 25 days of age (doa), against Mhyo and PCV2 with INGELVAC MHYO® and SUVAXYN PCV® by intra-muscular route (IM) and vaccinated against PRRSv between 40 and 45 doa with PORCILIS PRRS® by intra-dermal route. The 491 piglets of the two last batches (group B) were vaccinated on the same day (around 25 doa) against the 3 pathogens with INGELVAC MYCOFLEX®, INGELVAC CIRCOFLEX® and INGELVAC PRRSFLEX®, by IM route. In this group, half of the piglets received an injection of INGELVAC MYCOFLEX® and INGELVAC CIRCOFLEX®, freshly mixed (according to the SPC of both vaccines), and an injection of INGELVAC PRRSFLEX® separately (B1). The other half received the 3 vaccines mixed together using a single injection (off label use) (B2). The mixture was prepared according to the following order: mixing of INGELVAC MYCOFLEX® and INGELVAC CIRCOFLEX® first then rehydration of INGELVAC PRRSFLEX® with this mixture. Strict internal biosecurity measures were applied to avoid direct and indirect contact between the two groups during the post-weaning and fattening period. All piglets were individually ear-tagged and weighed at inclusion. Ten piglets from each batch were blood sampled every 3 weeks from weaning to 24 weeks of age (woa).
Studied parameters:
Respiratory counts: Every 3 weeks, from 6 to 24 woa, cough counts were done during 3 minutes in each room.
Technical data: Average Daily Gain (ADG) from day of inclusion to slaughter were calculated on 577 animals in group A and 444 in group B (due to deaths or slaughterhouse missing datas). Mortality rate per batch was recorded.
Serological and virological follow up: Serologies against Mhyo (Mycoplasma antibody Test Kit, Idexx Laboratories Inc., Maine, USA) were performed at each sampling time and PCV2 qPCR (1) performed at 3, 9, 15 and 21 woa (sera pooled by 3 or 4).
Statistics: Regarding ADG, we performed a non-inferiority analysis considering a noninferiority margin Δ = -5g. Due to room, batch and weight at inclusion effects, an ANCOVA test was used. We used descriptive statistics for the other data.
RESULTS
Overall, there was no clinical relevant difference regarding cough counts between the two groups. However at 18 and 21 woa, the percentages of cough were lower in group B.
The confidence interval (CI) for adjusted ADG was [-4.01; 15.02]. The low limit of the CI being above Δ=-5g, non-inferiority is proven. There was no relevant difference between groups regarding mortality. We observed a Mhyo seroconversion in the second period of the finishing stage for both groups. However, the seroprevalence and the percentage of pigs with titer over 1.5 were higher in group A than in group B. All the PCV2 qPCR were negative suggesting an absence of virus circulation in both groups.
CONCLUSION
The respiratory counts and the serological kinetics (2) seem to show that Mhyo infection pressure was higher in group A. However, the interpretation of Mhyo serological data in vaccinated pigs is a challenge for practitioners, especially because serological responses vary between vaccines. We should probably have done Mhyo qPCR on tracheal mucus to definitively conclude on a circulation of the bacteria (3). Regarding technical parameters, the different vaccinations protocols provided the same results.