Equine Infectious Anemia & Potomac Horse Fever 2025: Vet‑Approved Guide

By Dr Duncan Houston BVSc 🩺

This guide covers two crucial equine diseases in 2025: Equine Infectious Anemia (EIA) and Potomac Horse Fever (PHF). Both pose significant risk—EIA as a lifelong viral infection with strict regulations, and PHF as an acute, often seasonal, bacterial illness. This article covers veterinary-approved understanding, detection, treatment, biosecurity, and prevention strategies to protect your horse and herd.

1. What Is Equine Infectious Anemia (EIA)? 🦠

EIA is a retrovirus infection transmitted primarily through biting flies, contaminated needles or syringes, and blood products. It affects all equids—horses, mules, donkeys—and is reportable in the U.S. with no cure; infected animals become lifelong carriers :contentReference[oaicite:3]{index=3}.

Signs & Stages

• Acute: high fever, severe anemia, swollen limbs or abdomen, rapid weight loss, sudden death (<60 days post-infection) :contentReference[oaicite:4]{index=4}.
• Subacute: recurrent fever, lethargy, mild anemia, spleen enlargement, swelling of chest and legs.
• Chronic/carrier: intermittent weakness, occasional fever, often asymptomatic yet infectious lifelong :contentReference[oaicite:5]{index=5}.

Diagnosis

The gold standard is the Coggins test (agar gel immunodiffusion), typically performed annually or for interstate travel :contentReference[oaicite:6]{index=6}.

What Happens If Positive?

• Infected horses must be euthanized or permanently isolated ≥ 200 yards from other equids :contentReference[oaicite:7]{index=7}.
• No treatment available—management focuses on prevention and regulatory control :contentReference[oaicite:8]{index=8}.

Prevention Strategies

• Annual Coggins testing for all equids.
• Strict needle/syringe protocols—single-use only.
• Avoid shared equipment and blood products unless tested virus-free.
• Biting fly control (screens, repellents) to reduce vector transmission :contentReference[oaicite:9]{index=9}.

Recent Outbreak Alert

In 2025, a multi-state EIA outbreak in the Southwest U.S. resulted in 21 horse deaths, traced to medical equipment reuse in vet clinics :contentReference[oaicite:10]{index=10}. Another Californian case in early 2025 underscored persistent regional risk :contentReference[oaicite:11]{index=11}.

2. What Is Potomac Horse Fever (PHF)? 🌿

PHF is caused by Neorickettsia risticii, an intracellular bacterium linked to aquatic insect ingestion. Infection is seasonal (late spring to autumn), especially near water bodies carrying infected trematode hosts :contentReference[oaicite:12]{index=12}.

Clinical Signs

• Acute fever (103–107 °F), lethargy, anorexia, mild colic :contentReference[oaicite:13]{index=13}.
• Profuse watery diarrhea, dehydration, limb edema due to protein loss :contentReference[oaicite:14]{index=14}.
• High laminitis risk (20–40%), and possible abortion in pregnant mares :contentReference[oaicite:15]{index=15}.
• Case fatality up to ~30%, mainly due to laminitis and shock :contentReference[oaicite:16]{index=16}.

Diagnosis

Confirmed via PCR from blood or feces—best early detection approach. Antibody tests are less reliable, especially post-vaccination :contentReference[oaicite:17]{index=17}. Routine bloodwork can show dehydration and electrolyte imbalance.

Treatment & Care

• IV oxytetracycline (6.6 mg/kg q12h for 5–7 days) is first-line—rapid improvement often within 12–24 h :contentReference[oaicite:18]{index=18}.
• Supportive care: IV fluids, NSAIDs, electrolyte therapy, laminitis prevention with ice boots, endotoxin binding agents :contentReference[oaicite:19]{index=19}.
• Hospitalization may be required in severe cases.

Prevention & Vaccination

• Annual spring vaccination—efficacy variable, booster recommended 3–4 weeks later in endemic regions :contentReference[oaicite:20]{index=20}.
• Reduce insect exposure—turn off outside lights, screen barns, cover feed/water :contentReference[oaicite:21]{index=21}.
• Pasture management—keep horses away from waterways during outbreaks :contentReference[oaicite:22]{index=22}.

3. Comparative Summary

4. Vet & Owner Cooperation 📋

Both diseases demand close veterinarian collaboration:

• Immediate Coggins testing for EIA suspicion or before travel.
• PCR testing for suspected PHF during summer outbreaks.
• Start treatment early—especially with PHF to prevent laminitis.
• Regular vaccination and biosecurity reviews in endemic areas.

5. Ask A Vet Support & Integration 📲

With Ask A Vet, you have access to:

• 🩺 Telehealth triage for fevers, colic, or early EIA/PHF signs.
• 📋 Lab coordination for Coggins, PCR, and blood panels.
• ▸ EIA: quarantine planning, vector management, regulatory navigation.
• ▸ PHF: vaccination scheduling, insect-proofing tactics, endpoint laminitis planning.
• 🗓 Reminders for annual Coggins, spring PHF boosters, and seasonal check-ins.

6. Final Takeaway 🧠

Equine Infectious Anemia and Potomac Horse Fever are serious but manageable with vigilance. In 2025, let veterinary insight guide your prevention—ahead through testing, biosecurity, treatment, and vaccination. Stay informed and proactive to protect your horse’s health and future.

Need help with disease risk assessment or outbreak readiness? Download the Ask A Vet app or visit AskAVet.com to connect with experts and ensure your equine wellness under Dr Duncan Houston’s guidance. 🐴

Disclaimer: This is for educational purposes; always consult a veterinarian for specific medical advice.