Porcine Intestinal Adenomatosis in Pigs: Chronic Form of Ileitis
- Porcine intestinal adenomatosis is the chronic, non-hemorrhagic form of ileitis caused by the bacterium Lawsonia intracellularis.
- It most often affects growing pigs and commonly causes loose manure, uneven growth, poor feed efficiency, and gradual weight loss rather than sudden collapse.
- Many pigs recover, but ongoing infection can lead to chronic poor body condition and, in some cases, progression to necrotic intestinal disease.
- Diagnosis usually involves your vet combining herd history, exam findings, fecal PCR or other lab testing, and sometimes necropsy or intestinal tissue testing.
- Treatment and control often include herd-level management changes, targeted antimicrobials chosen by your vet, and vaccination programs to reduce future losses.
What Is Porcine Intestinal Adenomatosis in Pigs?
Porcine intestinal adenomatosis, often shortened to PIA, is the chronic form of porcine proliferative enteropathy, also called ileitis. It is caused by Lawsonia intracellularis, a bacterium that infects cells lining the intestine. The infection leads to abnormal thickening of the intestinal wall, especially in the ileum, which is the last part of the small intestine.
In the chronic form, pigs usually do not look critically ill at first. Instead, pet parents and producers may notice loose stool, slower growth, reduced feed conversion, and pigs that fall behind their pen mates. This matters because even mild, ongoing intestinal disease can affect comfort, body condition, and overall herd performance.
PIA is different from the acute hemorrhagic form of ileitis, which can cause sudden bleeding and death. Chronic disease is usually less dramatic, but it still deserves veterinary attention because it can linger, spread through groups of pigs, and sometimes progress to more severe intestinal damage.
Your vet can help determine whether the problem is likely ileitis or another cause of diarrhea and poor growth, such as salmonellosis, swine dysentery, parasites, diet change, or other enteric infections.
Symptoms of Porcine Intestinal Adenomatosis in Pigs
- Loose to watery diarrhea
- Reddish-brown or faintly blood-tinged manure
- Poor weight gain or pigs falling behind pen mates
- Progressive loss of body condition
- Reduced appetite or inconsistent feed intake
- Rough hair coat and unthrifty appearance
- Lethargy or reduced activity
- Black, tarry stool, marked weakness, or pale skin
Chronic ileitis often starts with subtle signs. A pig may keep eating but grow poorly, look tucked up, or have intermittent loose manure. In group settings, the first clue may be uneven weights across the pen rather than one obviously sick pig.
See your vet immediately if you notice black or tarry stool, obvious blood in manure, sudden weakness, pale skin, collapse, or rapid losses in multiple pigs. Those signs can suggest a more severe form of ileitis or another serious intestinal disease that needs urgent veterinary guidance.
What Causes Porcine Intestinal Adenomatosis in Pigs?
The cause is infection with Lawsonia intracellularis, an intracellular bacterium spread mainly by the fecal-oral route. Pigs become infected by swallowing the organism from contaminated manure, pens, equipment, boots, transport surfaces, or shared environments. Pig-to-pig spread is important, especially where groups are mixed or facilities are continuously occupied.
Stress can make clinical disease more likely. Common triggers include weaning, moving pigs, commingling groups, crowding, weather shifts, and other disease pressure. In some pigs, infection stays mild or subclinical. In others, the intestinal lining becomes thickened and inflamed enough to cause chronic diarrhea and poor growth.
Age matters too. Chronic ileitis is most often recognized in growing pigs, commonly from about 6 to 20 weeks of age, though the broader non-hemorrhagic form is often described in pigs weighing roughly 40 to 80 pounds. Co-infections and overall herd health can influence how severe the disease becomes.
Because several intestinal diseases can look similar, your vet should help sort out whether Lawsonia is the main problem or part of a larger herd-health issue.
How Is Porcine Intestinal Adenomatosis in Pigs Diagnosed?
Diagnosis starts with the pattern of disease. Your vet will look at age group, manure changes, growth performance, recent stressors, and whether multiple pigs are affected. A physical exam and herd history help narrow the list, but signs alone are not enough to confirm ileitis.
Common testing options include fecal PCR for Lawsonia intracellularis, intestinal tissue testing, and necropsy of freshly affected pigs. In some cases, histopathology with special staining or immunohistochemistry is used to confirm the characteristic intestinal changes and identify the organism in the tissue. Serology may also be used more for herd monitoring than for diagnosing one individual pig.
Your vet may also recommend testing for other causes of diarrhea, such as Salmonella, Brachyspira, PEDV, TGE, parasites, or dietary causes. That broader approach matters because mixed infections are common in pigs, and treatment plans can change depending on what else is present.
If several pigs are affected, submitting samples from untreated, freshly sick animals usually gives the best chance of a useful answer. Your vet can guide which samples to collect and where to send them.
Treatment Options for Porcine Intestinal Adenomatosis in Pigs
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm call or herd-health consultation with your vet
- Isolation or closer observation of affected pigs
- Supportive care plan for hydration, feed access, and environmental comfort
- Targeted fecal PCR or limited diagnostic testing
- Herd management changes such as reducing stress, improving sanitation, and tightening traffic flow
Recommended Standard Treatment
- Complete veterinary assessment of affected pigs and the group
- Fecal PCR or enteric disease panel, with necropsy when appropriate
- Vet-directed antimicrobial plan where legal and appropriate for swine use
- Review of feed, stocking density, movement, and sanitation practices
- Vaccination planning for at-risk groups if your vet feels it fits the herd situation
Advanced / Critical Care
- Expanded herd investigation with multiple diagnostics and postmortem evaluation
- Testing for co-infections and broader enteric disease surveillance
- Customized vaccination and biosecurity redesign with your vet
- Intensive treatment protocols for severely affected groups
- Ongoing herd-health monitoring and follow-up performance review
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Porcine Intestinal Adenomatosis in Pigs
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look most consistent with chronic ileitis, or should we also test for Salmonella, Brachyspira, parasites, or viral diarrhea causes?
- Which pigs should we sample first, and do you recommend fecal PCR, necropsy, or both?
- Are there signs that this chronic case could progress to a more severe hemorrhagic form?
- What treatment options are appropriate and legal for my pigs based on age, use, and current regulations?
- Would vaccination help in this herd, and if so, when should pigs be vaccinated?
- What management changes would most reduce spread right now, such as all-in/all-out flow, cleaning, or reducing mixing?
- How should we monitor recovery: manure quality, weight gain, feed intake, or repeat testing?
- What is the likely cost range for diagnostics, treatment, and prevention over the next group of pigs?
How to Prevent Porcine Intestinal Adenomatosis in Pigs
Prevention focuses on lowering exposure to Lawsonia intracellularis and reducing the stressors that let infection flare into disease. Good manure management, regular cleaning and disinfection, limiting traffic between groups, and keeping boots, tools, and transport surfaces clean all help reduce spread. Rodent and wildlife control also matter because contaminated environments can keep enteric disease pressure high.
Group flow is important. All-in/all-out management is generally safer than continuous flow because it allows pens to be emptied, cleaned, and rested between groups. Avoiding unnecessary mixing, overcrowding, and abrupt feed or environment changes can also reduce the chance that subclinical infection becomes clinical disease.
Vaccination is a common prevention tool in at-risk herds. Available products in the U.S. include oral and injectable options against Lawsonia intracellularis. Your vet can help decide whether vaccination fits your pigs' age, housing, and disease history, and how to time it around other herd-health steps.
If you bring in new pigs, quarantine and herd-health review are wise. Even one infected animal can contribute to spread, so prevention works best when biosecurity, monitoring, and veterinary planning are used together.