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Doctoral thesis2010Open access

Actinobacillus pleuropneumoniae : a major respiratory pathogen in pigs

Sjölund, Marie


Actinobacillus pleuropneumoniae is a major cause of respiratory disease in pigs, causing animal suffering and substantial economic losses. The aim of this thesis was to obtain more knowledge on the protective immunity to infections with A. pleuropneumoniae and to evaluate potential strategies in preventing and combating A. pleuropneumoniae infections. Investigations regarding the role of maternal immunity for the protection of the offspring and the subsequent effect on the epidemiology on herd level demonstrated that the levels of serum antibodies to A. pleuropneumoniae in sows were reflected in colostral levels. The colostral levels were in turn reflected in the levels of serum antibodies in the offspring and piglets with high levels of antibodies also had detectable levels of antibodies for a longer time compared to the offspring to sows with low levels of antibodies to A. pleuropneumoniae. An inoculation of naïve pigs with A. pleuropneumoniae induced acute-phase protein responses. The response to the inoculation was clearly affected by the antimicrobial treatment administered at the onset of clinical signs of respiratory disease. The response of these pigs to a second inoculation was also influenced by the treatments carried out after the first inoculation. Enrofloxacin was superior in reducing clinical signs but left pigs unprotected at the second inoculation. Tetracycline demonstrated a similar treatment efficacy as enrofloxacin but pigs were protected at challenge as were the penicillin treated pigs. Penicillin was on the other hand not efficient in curing diseased pigs. The pigs that were protected from disease at the second inoculation had all developed serum antibodies to A. pleuropneumoniae following the first inoculation and an acute-phase response was not induced following the second inoculation. The results therefore indicate that antibodies mirror protection against disease well. Vaccinations against actinobacillosis in a fattening herd did not provide protection against clinical disease. However, in combination with intensified treatments of pigs with signs of respiratory disease, pleurisy registrations at slaughter decreased over time although the growth rate was unaffected.


swine; actinobacillus pleuropneumoniae; immunity; vaccination; disease control; animal health; immunology

Published in

Acta Universitatis Agriculturae Sueciae
2010, number: 2010:73
ISBN: 978-91-576-7518-7
Publisher: Dept. of Clinical Sciences, Swedish University of Agricultural Sciences