Lawsonia-Linked Diarrhea in Foals by a Vet – 2025 Diagnosis & Treatment Guide 💩🐴
In this article
Lawsonia-Linked Diarrhea in Foals by a Vet – 2025 Diagnosis & Treatment Guide 💩🐴
By Dr Duncan Houston, BVSc
Introduction
Lawsonia intracellularis is a bacterium that causes a serious and emerging intestinal disease in weanling foals. First recognized more widely in recent decades, this infection has now become endemic on many farms in 2025. Affecting foals between 3 to 13 months of age, it presents with diarrhea, fever, colic, and protein loss, often requiring veterinary hospitalization and intravenous care. With early detection and treatment, prognosis is excellent.
What Is Lawsonia? 🦠
- Lawsonia intracellularis is a gram-negative, intracellular bacterium.
- It causes a disease known as Equine Proliferative Enteropathy (EPE).
- The bacterium infects the small intestine, leading to thickening of the gut wall and poor nutrient/protein absorption.
- Though more common in pigs, Lawsonia has now become a recognized cause of serious disease in foals globally.
Who Is Affected? 👶🐴
- Primarily foals aged 3 to 13 months—often post-weaning.
- High-risk environments: high-traffic breeding farms or those with prior outbreaks.
- Endemic farms: once the bacterium is present, recurrence among future foals is likely without intervention.
Clinical Signs to Watch For ⚠️
- Diarrhea (mild to profuse)
- Fever (often persistent)
- Lethargy and dullness
- Weight loss and poor body condition
- Colic or abdominal discomfort
- Subcutaneous edema (especially along the belly, limbs, or jaw)
- Decreased appetite
Why Edema Occurs 💧
Lawsonia interferes with nutrient absorption—especially proteins. Low protein (hypoproteinemia) reduces oncotic pressure in the bloodstream, causing fluid to leak into surrounding tissues. Edema is a red flag symptom that differentiates Lawsonia from many other causes of foal diarrhea.
Diagnosis 🧪
A combination of clinical signs and diagnostics is needed:
- Ultrasound: Thickened small intestinal wall (proliferative enteropathy)
- Fecal PCR test: Detects Lawsonia DNA
- Bloodwork: Shows low total protein and hypoalbuminemia
- Serum antibody tests: Help confirm exposure
Early Isolation Is Key 🛑
- Separate symptomatic foals immediately
- Limit handling contact and disinfect stalls/equipment
- Monitor other foals on the farm for early signs or protein drops
Treatment Plan 💊
Successful outcomes depend on aggressive early intervention:
1. Antibiotics (Must Target Intracellular Pathogens)
- Oxytetracycline (IV) or doxycycline (oral)
- Chloramphenicol or macrolides as alternatives (use with caution)
2. Supportive Therapy
- IV fluids to combat dehydration
- Plasma transfusion to restore protein levels
- Anti-ulcer medication (omeprazole or sucralfate)
- Electrolyte support and nutrition as needed
Prognosis & Recovery 📈
- Excellent with early, appropriate care
- Most foals recover within 1–3 weeks
- Delayed treatment increases risk of complications or chronic gut changes
Preventive Strategies in 2025 🧼
1. Surveillance & Screening
- Test weanlings in endemic areas proactively during fall and spring
- Monitor total protein levels routinely
2. Isolate Sick Foals
- Maintain 3-week isolation protocol after symptoms resolve
- Clean stalls and rotate turnout
3. Biosecurity
- Control rodent populations and avoid shared feed bins
- Disinfect barns, trailers, and shared foal gear
Vaccine Use 💉
- Currently, a swine vaccine is used off-label with success in foals under vet supervision
- Vaccination shows promise for farms with annual Lawsonia outbreaks
- Ongoing research continues for a licensed equine-specific vaccine
Case Example: Foal Recovery
- A 6-month-old weanling on an endemic farm developed fever, dullness, and mild edema.
- Ultrasound showed thickened gut; PCR was positive for Lawsonia.
- IV antibiotics and plasma administered; supportive fluids given for 5 days.
- Foal recovered fully after 12 days of care and returned to pasture.
FAQs About Lawsonia in Foals
Q: Can adult horses get Lawsonia?
A: Very rarely. It’s primarily a weanling disease.
Q: Is Lawsonia contagious?
A: Yes—transmitted fecal-orally between foals. It can persist in the environment if not disinfected properly.
Q: Does a vaccine exist?
A: A swine vaccine is used off-label; equine-specific options are under development.
Conclusion
Lawsonia is now a common cause of illness in young foals, with symptoms ranging from diarrhea to life-threatening protein loss. Fortunately, early diagnosis, antibiotics, and plasma treatment provide excellent recovery chances. Farms with a history of Lawsonia should be proactive with screening and prevention. Contact your vet at the first sign of fever, weight loss, or edema in a weanling.
Need help diagnosing a foal or preventing Lawsonia on your farm? Visit AskAVet.com or download the app 📱 to speak with Dr Duncan Houston and our expert team for real-time guidance. 🩺🐴
