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Vaccination Controlled - But Did Not Prevent - APP

by 5m Editor
7 April 2010, at 8:58am

SWEDEN - Vaccination did not prevent the clinical expression of A. pleuropneumoniae (APP) infections but it did activate the immune system of fattening pigs, according to researchers based in Uppsala.

Marie Sjölund of the National Veterinary Institute and Per Wallgren of the Swedish University of Agricultural Sciences – both in Uppsala – have published a paper on thier field experiences with two vaccination strategies to control Actinobacillus pleuropneumoniae (APP) in fattening pigs in Acta Veterinaria Scandinavica.

They say that the prevalence of pleurisies recorded at slaughter is increasing in Sweden, and acute outbreaks of actinobacillosis that require antimicrobial treatments have become more frequent. As an increased use of antimicrobials may result in the development of antimicrobial resistance it is essential to develop alternative measures to control the disease. Vaccinations present an appealing alternative to antimicrobial treatments. The aim of their work was to evaluate the potential of two different vaccination strategies in a specialized fattening herd affected by actinobacillosis.

Methods

The study was conducted in a specialised fattening herd employing age segregated rearing in eight units. The herd suffered from infections caused by Actinobacillus pleuropneumoniae serotype 2, confirmed by necropsy and serology.

The study included 54 batches of pigs grouped into five periods. Batches of pigs of the second period were vaccinated against actinobacillosis twice, and pigs in the fourth period were vaccinated three times. The vaccine used was Porcilis® APP from Intervet. Batches of pigs of the first, third and fifth period were not vaccinated.

Concentrations of serum antibodies to A. pleuropneumoniae and serum amyloid A (SAA) were analysed and production data were recorded.

Results

Despite vaccinating, medical treatments were required to reduce the impact of the disease. The mean incidence of individual treatments for respiratory diseases during the rearing period ranged from 0 to 4.7 ± 1.8 per cent, and was greatest during the triple vaccination period (period IV; p<0.05 when compared to other groups). A large proportion of the vaccinated pigs seroconverted to A. pleuropneumoniae serotype 2 in the absence of a SAA-response.

The prevalence of pleuritis decreased from 25.4 ± 6.5 per cent in the first period to 5.0 ± 3.7 per cent in the fifth period (p<0.001).

Conclusions

Sjölund and Wallgren concluded that the vaccine did not effectively prevent clinical expression of A. pleuropneumoniae infections. However, they pointed out that seroconversion to A. pleuropneumoniae in the absence of a SAA-response in a large number pigs indicated that the vaccine had activated the immune system. Furthermore, the prevalence of pleuritis decreased with time. This indicates that vaccinations together with intensified medical treatments of affected pigs could be useful in reducing the impact of A. pleuropneumoniae serotype 2 infections, concluded the researchers.

Reference

Sjölund M. and P. Wallgren. 2010. Field experience with two different vaccination strategies aiming to control infections with Actinobacillus pleuropneumoniae in a fattening pig herd. Acta Veterinaria Scandinavica 52:23. doi:10.1186/1751-0147-52-23

Further Reading

- You can view the full report (as a provisional PDF) by clicking here.
- Find out more information on Actinobacillus pleuropneumonia (APP) by clicking here.

5m Editor