Seroprevalence of porcine proliferative enteropathy before initiating vaccine marketing in Korea

Abstract

Abstract : Proliferative enteropathy caused by Lawsonia intracellularis is one of the most common enteric diseasesin pigs. The objective of this study was to determine the prevalence of serum antibodies against L. intracellularisin the general swine population of Korea from 2005 to 2008. In total, 8,008 swine serum samples obtained from1,001 herds were tested. The samples were analyzed with an immunoperoxidase monolayer assay to detect anti-L.intracellularis antibodies. The overall 4-year average true prevalence was 40.0% (CI: 39.4 - 40.6%) at the individualanimal level and 71.9% (CI: 70.3-73.4%) at the herd level.Keywords : Korea, Lawsonia intracellularis, prevalence, proliferative enteropathy, serology In the pig farming industry, enteric diseases are a problemof increasing importance. Porcine proliferative enteropathy(PPE) caused by Lawsonia (L.) intracellularis is one of themost common enteric diseases in grower and finisher pigs.Information regarding the distribution of this pathogen inswine herds at the country level would be beneficial for thedevelopment of control protocols. In the Republic of Korea(ROK), the reported prevalence of PPE has varied by study,ranging from 3.3% to 56% at the pig level and from 20% to100% at the herd level [6, 7, 12]. However, all studies on theprevalence of PPE in the ROK have targeted only selectedherds with a history of diarrhea or only pigs with diarrhea.The objective of our study was to determine the prevalenceof serum antibodies to L. intracellularis in the general swinepopulation in the ROK. It is important to note that the aviru-lent live L. intracellularis vaccine (Enterisol Ileitis; BoehringerIngelheim Animal Health, Germany), which is the first andonly vaccine for the control of PPE, was not available for usein pigs in the ROK until the time of sampling; thus, thedetected antibodies could not have been elicited by the L.intracellularis vaccine.The swine serum samples were randomly obtained fromserum specimen sources obtained under the Korea NationalAnimal Health Monitoring Project, which was conductedfrom 2005 through 2008. The study included 1,001 ran-domly selected herds distributed throughout the country.Samples were taken from 8 pigs from each herd. The serumsamples were analyzed by an immunoperoxidase monolayerassay (IPMA) to detect the L. intracellularis antibody. Usingthe pathogenic isolate PHE/KK421 [15], IPMA was per-formed. Briefly, the acetone-methanol-fixed L. intracellu-laris culture plate was incubated with sera diluted 1 : 30 inphosphate-buffered saline (PBS) at a volume of 50 µL perwell for 30 min at 37