Improved diagnostics and clinical applications for the detection and control of proliferative enteropathy

Lawsonia intracellularis, the etiological agent of proliferative enteropathy (ileitis, PE), is a major cause of economic losses in the global swine industry. Lawsonia intracellularis is a motile, Gram negative, microaerophilic, obligately intracellular pathogen that relies on host cellular interactions for survival and growth. Despite extreme difficulties in isolating L. intracellularis from infected pigs, advancements in the cultivation of this organism in vitro has led to better understanding of the pathogenesis of PE, the development of sensitive and specific diagnostic techniques and methods for the control and prevention of this disease;This dissertation describes the development of a novel enzyme-linked immunosorbent assay (ELISA) for improved detection of L. intracellularis exposure in pigs. This immunoassay utilizes the LPS-component of L. intracellularis as its primary antigen in an indirect ELISA format. Also described in this dissertation are studies used to evaluate the efficacy of a newly attenuated European-derived isolate of L. intracellularis in pigs vaccinated orally by two different routes of administration at three weeks of age, then challenged with a virulent pure culture heterologous isolate of L. intracellularis. Finally, in vivo experiments were conducted to evaluate the effectiveness of vaccine against virulent challenge when administered orally to pigs maternally positive with anti-Lawsonia antibodies at 3 weeks of age. The use of an LPS-based ELISA will provide better understanding of the onset of exposure to L. intracellularis allowing for more precise vaccine placement for the control and prevention of PE in pigs. Improved detection systems along with innovative methods of vaccine delivery will provide swine producers and veterinarians more options for the control of PE resulting in better performance and less cost to market