In contrast, pigs that had been at the herd for 30 days had lower serum antibody levels to A

In contrast, pigs that had been at the herd for 30 days had lower serum antibody levels to A. fourth period were vaccinated three times. 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%, 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% in the first period to 5.0 3.7% in the fifth period (p < 0.001). Conclusions The vaccine did not effectively prevent clinical expression of A. pleuropneumoniae infections, but seroconversion to A. pleuropneumoniae in the absence of a SAA-response in a large number pigs indicated that the vaccine had activated Demethoxydeacetoxypseudolaric acid B analog the immune system. Further, 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. Background Actinobacillus pleuropneumoniae is a causative agent PLA2G4 of respiratory disease in pigs with symptoms ranging from sudden deaths to subclinical disease detected as pleurisies in the post mortem inspection at slaughter [1]. Infections with A. pleuropneumoniae may cause great economic losses due to mortality, increased feed consumption, retarded growth rate and medication [1-3]. Several strategies have therefore been employed aiming to control the effects of A. pleuropneumoniae infections of which age segregated rearing is one [4,5]. The ban on the use of growth promoters in Sweden in 1986 led to a more consistent implementation of age segregated rearing systems [6] which reduced the incidence of pleurisies recorded at slaughter from 8% in 1988 to 5% in 2002 [7]. However, registrations for pleurisies at slaughter are currently increasing and acute outbreaks of actinobacillosis are becoming more frequent [8]. Such outbreaks often require antibiotic treatment of entire units with in-feed medication which has been mirrored by an increased prescription of tetracyclines in 2007 [9]. To date, none of the tested Swedish isolates of A. pleuropneumoniae have been resistant to the antibiotics tested for [9]. Despite this, it is essential to develop antibiotic independent measures to control the disease since an increased use of antibiotics may promote the emergence of antimicrobial resistance [10]. Antimicrobial resistance for A. pleuropneumoniae isolates has been reported [11]. Vaccination presents an appealing alternative to antibiotics in reducing the impact of A. pleuropneumoniae. The first generation of vaccines against A. pleuropneumoniae did not provide sufficient protection against disease and were in some cases causing adverse side effects such as depression, inappetence, fever or tissue damage [12]. At present, one subunit vaccine is commercially available in Sweden (Porcilis? APP, Intervet, Boxmeer, The Netherlands). Several reports from different countries have described the efficacy of this vaccine [13,14]. According to the product details, this vaccine induces a gradually developing Demethoxydeacetoxypseudolaric acid B analog protective immunity which is greatest two to three weeks after booster vaccination with some protection maintained for up to seven weeks. This work aimed at evaluating the effect over time of two different vaccination strategies in a specialized fattening herd affected by actinobacillosis. Methods Herd and batches followed in a longitudinal survey The study was approved by the Ethical Committee on Animal Experiments, Uppsala, Sweden (Licence C38/4). It was conducted in a conventional, specialized fattening herd producing approximately 7500 pigs per year. The herd was free from all diseases listed by the Office International des Epizooties, Paris, France, and also from Aujeszky’s Demethoxydeacetoxypseudolaric acid B analog disease, PRRS and Salmonella. However, the herd had suffered from infections caused by Actinobacillus pleuropneumoniae serotype 2 for two years, which had been confirmed by necropsy and serology. Batch prevalence at slaughter for pleurisy lesions ranged from 18.7% to Demethoxydeacetoxypseudolaric acid B analog 26.8% and for Mycoplasma hyopneumoniae-like lesions from 1.7% to 19.2% during the years preceding the study (see also Table ?Table11). Table 1 Lesions of.