Seroprevalence of Lawsonia intracellularis Antibodies among Large-scale Swine Farming Systems in Thailand

Gastrointestinal infectious diseases caused by bacteria have been a major problem in the swine industry, including Thailand. Porcine proliferative enteropathy (PPE), also known as porcine ileitis, is an enteric infectious disease caused by Lawsonia intracellularis – an obligate intracellular bacterium. PPE has been an economic threat to the global pork production system due to various types of diarrheas. Serological diagnosis can be applied to the seroprevalence of pathogen-antibodies and the timing of L. intracellularis infection when introduced to the herd. This present study showed the current serological status and the seroprevalence of antibodies against L. intracellularis in large-scale Thai swine herds using a commercial blocking enzyme-linked immunosorbent assay (ELISA). A total of 1,234 serums were sampled from 24 non-vaccinated commercial pig farms across Thailand as part of a monitoring program. The converted-herd seroprevalence was obtained in a total of 20 out of 24 herds sampled, and the within-herd seroprevalence was 51.0% (45.5-56.6%); older animals exhibiting higher seropositivity (93.8%, 95% CI: 80.5-100% and 100%, 95% CI: 100-100% in finishers and breeding pigs, respectively). Furthermore, the intensive-larger farms located in Northern Thailand manifested a 100% (95% CI: 100-100%) seropositive incidence as the highest frequency of Lawsonia-antibodies, followed by the Western (84.2%, 95% CI: 61.5-100%) and Eastern (69.1%, 95% CI: 56.4-81.0%) areas. There was a significant difference in the within-herd prevalence between site production systems (P < 0.001). Finally, in the absence of the L. intracellularis vaccine, porcine ileitis seroprevalence in large commercial swine herds in Thailand was prevailing.