Ileitis in Pigs: Lawsonia Infection, Poor Growth, and Intestinal Bleeding

Ileitis in pigs is an intestinal disease most often caused by the bacterium Lawsonia intracellularis. Vets may also call it porcine proliferative enteropathy. The infection targets cells lining the intestine, especially the ileum, and causes those cells to keep multiplying instead of maturing normally. That thickened, inflamed intestine cannot absorb nutrients as well, so affected pigs may grow poorly, lose condition, or develop diarrhea.

This condition does not always look dramatic at first. Some pigs have a mild or even subclinical infection and mainly show slower weight gain and uneven performance. Others develop more serious disease, including chronic intestinal damage or a hemorrhagic form with intestinal bleeding. In those cases, pigs may look pale, weak, and suddenly very ill.

Ileitis is most common in growing-finishing pigs and young breeding pigs, but the severity can vary by age, stress level, housing, and herd exposure. Because the same organism can be present in many swine herds, your vet usually interprets test results alongside symptoms, lesions, and herd history rather than relying on one test alone.

The main cause of ileitis is infection with Lawsonia intracellularis, a small intracellular bacterium spread largely by the fecal-oral route. Pigs become infected by taking in contaminated feces, manure particles, or material from an environment where infected pigs have been shedding the organism. Once inside the intestine, the bacteria invade intestinal lining cells and trigger abnormal cell proliferation, especially in the ileum.

Not every exposed pig becomes severely sick. Disease expression is influenced by age, stocking density, sanitation, transport, feed changes, mixing groups, and other stressors that affect gut health and immunity. Some pigs recover on their own, while others develop chronic necrotic intestinal disease or sudden hemorrhagic enteritis.

Herd context matters. Lawsonia is considered endemic in many swine populations, so a positive fecal PCR does not always mean it is the only cause of illness. Mixed infections are common, and your vet may also consider salmonellosis, Brachyspira infection, parasites, dietary factors, and gastric ulcers when a pig has diarrhea, poor growth, or melena.

Diagnosis starts with the basics: age group affected, recent stressors, stool changes, growth performance, and whether there have been sudden deaths. Your vet may examine individual pigs and the group, then recommend testing based on whether the problem looks like mild poor-doing, active diarrhea, or a bleeding emergency.

Common testing options include fecal, rectal swab, oral fluid, or ileal tissue PCR for Lawsonia intracellularis. These tests are useful, but they have limits. Because Lawsonia can be present in many herds, detection alone may not prove it is causing the current outbreak. That is why your vet may pair PCR with necropsy, histopathology, silver stain, or immunohistochemistry to confirm the organism within characteristic intestinal lesions.

Your vet may also recommend additional testing to rule out other important causes of enteric disease, especially Salmonella and swine dysentery. In practical terms, that can mean submitting fresh and fixed intestinal samples from acutely affected pigs, ideally early in the course of disease and before medication changes if possible. Rapid, well-targeted sampling often gives the clearest answers.

Prevention usually works best as a herd plan rather than a single product or one-time treatment. Good manure control, all-in/all-out flow when possible, careful cleaning between groups, and reducing stress from overcrowding, transport, or abrupt feed changes can all help lower exposure and disease expression. Consistent observation matters too, because catching mild diarrhea or poor growth early can prevent bigger losses later.

Vaccination is an important option in many herds. Commercial ileitis vaccines are available, including oral live vaccine programs and injectable options used in swine production. Your vet can help decide whether vaccination fits your pig's age, housing, and risk pattern, and how to time it around other herd health steps.

Biosecurity also matters. Avoid introducing pigs of unknown health status without a plan, and separate sick animals when practical. If ileitis has been confirmed before, your vet may recommend routine monitoring with strategic PCR testing, necropsy of fresh deaths, and periodic review of growth performance so problems are addressed before hemorrhagic disease appears.