Seroprevalence of Lawsonia intracellularis antibody among swine herds in Thailand, December 2021-March 2022

Abstract

The gastrointestinal infectious diseases caused by bacteria have been a major problem in the Thai swine industry. Porcine proliferative enteropathy (PPE), also known as porcine ileitis, is an enteric infectious disease caused by Lawsonia intracellularis. Porcine ileitis has been an economic threat to the global pork production system due to various types of diarrheas. Serological diagnosis can be applied for determining pathogen-antibodies seroprevalence and the timing of L. intracellularis infection when introduced to the herd. A lack of serological data since 2009, as well as recent antibiotic usage restrictions, may have a negative impact on porcine ileitis seroprevalence in Thailand. Hence, the objective of this present study was to investigate the current serological status and the seroprevalence of antibodies against L. intracellularis in large-scale swine herds in Thailand 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 herd seroprevalence was obtained in a total of 22 out of 24 herds sampled, and the within-herd seroprevalence was 50.5% (95% CI: 47.7-53.3%), with higher seropositivity detected in older animals. Furthermore, the most Lawsonia-antibodies were found in the intensive larger farms in Northern Thailand. There was a significant difference in the within-herd seroprevalence between single-site and multiple-site production systems (P < 0.001). Here, the finding confirmed that in the absence of the L. intracellularis vaccine, PPE seroprevalence in large commercial swine herds in Thailand was prevailing.