Poster Immunology - Immune response and immunity 588 Proceedings of the 23rd IPVS Congress, Cancun, Mexico – June 8-11, 2014 P.608 The use of cross-sectional serological profile for appropriate implementation of A. pleuropneumoniae vaccination program in farrow-to-finish farms E Czyżewska, A Dors, M Pomorska-Mól, K Kwit, P Kwieciński, P Matyba, J Wojciechowski, Z Pejsak Department of Swine Diseases, National Veterinary Research Institute, Pulawy, Poland, z.pejsak@piwet.pulawy.pl Introduction Porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae (App) may cause serious economic losses, especially in fattening units (1). Usually, control of pleuropneumonia in endemically infected herds requires combinations of vaccination, medications and improved husbandry. Commercially available vaccines can reduce clinical symptoms and improve performance. Generally, vaccination is recommended in pigs at 6 week of age or older. However, vaccination at early age may be ineffective due to interference with maternally derived antibody (MDA) which with regard to App may persist for 12 weeks (1, 2). Materials and Methods Three farrow-to-finish herds (A–C) with histories of App infections were selected. Vaccination against App was not carried out in these herds. In all herds piglets were weaned at 28 day of age. Serum samples were taken from 10 pigs of 3, 6, 9, 12, 15 and 18 weeks of age. For detection of specific antibodies against App commercial ELISA test were used: The APP-ApxIV ELISA test kit (IDEXX). Results In herd A, antibodies to App were detected in at least 60% of pigs till 9 weeks of age. At 12 weeks of age none of examined animals have detectable antibodies. The prevalence of antibody was increased thereafter, and reached 90% of pigs at age 18 weeks (Figure 1.). The same trend (decrease followed by increase) was also observed with regard to the S/P value. In herd B, antibodies to App were detected in at least 50% of animals till 9 weeks of age. Seroprevalence of App-specific antibodies increased slightly at the 12 week of age (60% of animals had App- specific antibodies) and continued to rise at the 15 and 18 week of age, reaching 80% and 100% respectively (Figure 2.). In herd C, MDA were detected in 100% of piglets at 3 weeks of age, 80% of pigs at 6 weeks of age and in 60% of 9 weeks old pigs. At age of 15 weeks none of the examined pigs have detectable antibodies to App. At the next sampling period (18 weeks of age) the seroprevalence increase to 80%, however S/P value were lower at that time compared to values observed in 3-6 week-old piglets (Figure 3.). Figure 1. Serum profile of App in herd A Figure 2. Serum profile of App in herd B Figure 3. Serum profile of App in herd C Discussion The results of present study showed that there were significant differences between the patterns of antibody circulation on various swine herd. In herds A and C, the MDA decayed to undetectable level at age of 12 or 15 weeks (herd A and C, respectively). In herd B there were no significant drop in the percentage of pigs with App-specific antibodies, and no clear border between MDA and post- infective antibodies could be identified. In all examined herds the significant increase of seropositive pigs was observed in fattening units. Information on the persistence of App-specific MDA and age at which pigs become infected with App are important for implementation of proper vaccination program. Because, antibody response after natural infection can be detected approximately 10-14 days post infection (1), the best age for the first vaccination of pigs in herd A is 8 weeks, and for the second 11 weeks. In herd C the best age for the vaccination is 10 and 13 weeks. In herd B onset of seroconversion was observed at around 12 weeks of age, thus the first vaccination should be done at 6 weeks of age, but at this age the high level of MDA was observed. Thus, to overcome the MDA interference, beside second vaccination at about 9 weeks of age, the third vaccination around 12-14 weeks should be considered (2). Summarizing, the serological profile could be a useful tool in planning a farm specific vaccination program. References 1. Gottschalk M. 2012. In: Zimmerman JJ, eds. Disease of swine. 10 th ed. Wiley-Blackwell, 653-669. 2. Jirawattanapong P. et al. 2008. J Swine Health Prod 16:193-199.