Equine Infectious Anemia (EIA) in Horses: Causes, Symptoms, Coggins Testing & Prevention
No vaccine. No cure. Here’s how EIA spreads, what to watch for, how testing and regulations work, and how to harden your barn against biting flies with a layered plan that includes Citraquin®.
Transmission & Disease Progression
Cause: EIA is a blood-borne retroviral disease of equids. It’s spread mainly by mechanical transmission on the mouthparts of large biting flies (horseflies and deerflies) that move small amounts of blood between horses. Iatrogenic spread (shared needles, transfusions, contaminated equipment) can also occur.
Progression: After exposure, some horses get sick quickly; others develop chronic, relapsing illness; many become inapparent carriers—infected for life without obvious signs, but still test-positive and subject to regulatory control.
Clinical Forms: Acute, Chronic & Inapparent
- Acute: fever, depression, anorexia, thrombocytopenia, anemia, possible edema (limbs/underline)
- Chronic: intermittent fever, weight loss, poor performance, recurring anemia/edema
- Inapparent carrier: no outward signs; remains EIA-positive for life
Heads-Up Stress—shipping, heavy work, illness—can trigger flare-ups in carriers. Work with your veterinarian on monitoring and risk reduction.
Coggins (AGID) vs. ELISA: How Testing Works
Coggins = AGID (Confirmatory)
The classic Coggins test (AGID) is the long-accepted confirmatory assay for EIA. It detects antibodies to EIAV and is widely recognized by regulators and events.
ELISA (Screening)
ELISA detects antibodies earlier and is commonly used for screening. Because early ELISAs can yield false positives, most jurisdictions confirm positives with AGID before regulatory action.
Timing It may take several weeks post-exposure for antibodies to reach detectable levels. Your vet may recommend re-testing exposed horses after a waiting period.
Reporting, Movement & Quarantine Rules
- Reportable disease: Labs and veterinarians must report positives to animal-health officials.
- Movement: Most shows, sales, boarding facilities, and interstate travel require a negative EIA test within the last 12 months (some use shorter intervals—follow your state/event rules).
- If positive: By regulation, EIA-positive horses are either humanely euthanized or placed under permanent quarantine with strict separation from other equids as directed by officials. Exposed herdmates remain under quarantine and are retested on the prescribed schedule.
Reality Check Requirements vary by state and event. Your veterinarian and state animal-health office are the final word on movement paperwork and quarantine specifications.
Fly Control & Biosecurity (Citraquin®)
Layered Vector Control
- Eliminate standing water; clean buckets/tanks; manage manure and weeds
- Stable during peak biting fly hours; use fans/screens and physical barriers
- Groom checks after turnout; fly masks/sheets when appropriate
- Never share needles; disinfect dental/floating and medical equipment
Add Citraquin® to the Routine
Use a natural, citronella-powered repellent as part of that stack:
Apply per label directions to help deter biting insects around horses as part of a larger prevention plan.
Supportive Care & Positive-Test Implications
- No cure, no vaccine: Care is supportive—quiet housing, shade/fans, hydration, nutrition, and vet-directed anti-inflammatories or transfusion support in select cases.
- Lifelong status: Infected horses remain positive for life; decisions about euthanasia vs. permanent quarantine are made with officials and your veterinarian.
- Paperwork & planning: Keep test certificates organized; know your destination’s entry rules before hauling.
EIA — FAQ
Are EIA-positive horses contagious to barnmates?
Not by casual contact. Transmission is mechanical via biting flies (or iatrogenic blood transfer). Still, regulations require euthanasia or permanent quarantine to eliminate risk.
How long is a Coggins valid?
Many jurisdictions and events require a negative within the previous 12 months; some require 6–12 months depending on risk and season. Always follow state and event rules.
Why do some positives look healthy?
Inapparent carriers may show no outward signs but remain infected for life—and subject to movement restrictions.
Can ELISA replace Coggins?
ELISA is great for screening and early detection. Most programs confirm ELISA positives with AGID (Coggins) before regulatory action.
What paperwork do I need to haul?
Typically a current negative EIA test (Coggins) and a Certificate of Veterinary Inspection (CVI/health certificate) for interstate travel. Your vet will advise based on destination.
Educational note: This article provides general information and is not a substitute for veterinary diagnosis or state/federal guidance. Always follow your veterinarian and your state animal-health officials.
