The underestimated disease
Ileitis or porcine proliferative enteropathy (PPE) is an infectious enteric disease caused by Lawsonia intracellularis. The organism and disease are present in all swine producing regions around the globe. In other words, Lawsonia intracellularis infection is a ubiquitous disease causing huge economic loss worldwide.
Lawsonia intracellularis is an obligate intracellular enteric pathogen, which means it grows and multiplies only within the intestinal cells. It is a gram-negative, curved rod that does not grow in conventional medium and only under anaerobic or microaerophilic conditions which makes it extremely difficult to isolate it.
Clinical Signs and Lesions
The disease occurs in two clinical forms, as PIA (Porcine Intestinal Adenomatosis) or as PHE (Proliferative Haemorrhagic Enteropathy). PIA is mostly observed in pigs 5-20 weeks of age, characterized by grey diarrhea and thickening of the intestinal mucosa. PHE primarily affects older pigs, gilts and boars. Bloody diarrhea is often accompanied by acute deaths in PHE affected pigs. Even when the disease is occurring in a mild form, with little or no obvious clinical signs, the economic impact can be enormous.
Diagnostics and Control
Diagnostics start with evaluating the disease history on farm, observing the clinical signs, conducting necropsies and taking the relevant samples. Diagnosis needs to be confirmed by laboratory tests including histology, detection of Lawsonia intracellularis antigen in tissue (IHC, PCR) and antibodies in serum (ELISA). While initial outbreaks of the disease might be treated with antibiotics, vaccination provides a more sustainable solution to protect pigs against the impact of Ileitis.
As Lawsonia intracellularis is an intracellular enteric pathogen, local and cellular immunity are most relevant for protection. The logical approach for a successful vaccine to control Ileitis is therefore a modified live vaccine that can be applied orally.