Equine infectious anemia

Equine Infectious Anemia (EIA) is a disease caused by a virus that affects all members of the equine family (horses, zebras, donkeys and donkeys).


Equine Infectious Anemia

Equine Infectious Anaemia (EIA)

What is

It is a disease caused by a virus that affects members of the equidae family (horses, zebras, donkeys, and mules).

The only defenses are prevention measures, laboratory diagnoses, and proper management.

There is legislation in place governing official equine health control programs in all countries, as it is a mandatory reporting disease. The reference serum test is Agar Gel Immunodiffusion Test (AGID), considered by the World Organisation for Animal Health (OIE) as the ‘gold’ standard test for Equine Infectious Anaemia.

Etiology of EIA:

Equine Infectious Anaemia (EIA) is a persistent viral infection caused by a virus RNA genome, highly mutagenic, which integrates into the host genome.

The EIA virus belongs to the Lentivirus genus of the family Retroviridae, a sub-family of the Orthoretrovirinae, and is genetically and antigenically related to other lentivirus of the genus, such as caprine arthritis encephalitis virus (CAEV), bovine immunodeficiency (BIV), feline immunodeficiency (FIV), human immunodeficiency 1, human immunodeficiency 2, and visna-maedi virus.

Equine Infectious Anaemia (EIA)


  • Recently Infected

    The horse may be recently infected with acute symptoms of the disease and a potential life expectancy of 2 or 3 weeks. However, the disease is only identified through the detection of an increase in body temperature that may go unnoticed by the caretaker. In general, however, the horse recovers and continues within the team. IEA is only detected through a routine AGID test.

  • Chronic Stage

    If the horse survives the chronic stage, it will present recurring symptoms of fever, spots on the mucosa, anaemia, edemas on the lower limbs, weight loss, anorexia.

  • Symptomless Carriers

    However, most horses are symptomless carriers. Yet, as most equines continue in service, this condition may transform into chronic or acute symptoms and when subject to excessive work, it  results in an acute attack and death.


Due to the persistence of the virus, antibodies detection confirm the presence of p26.

Serology Test:


Due to the persistence of EIAV in infected equidae, detection of EIAV antibodies confirms the infection. For this purpose, the p26 protein of the viral core is employed for diagnosis purposes.

To clarify and by way of example, the virion contains:

gp90 virus envelope protein, between 60% and 70% of mutations in the env gene are located in the sequences that codify gp90, given a quantity of mutations 3 times greater than the changes in gp45; by contrast to gp90, the envelope sequence of gp45  is highly conserved in all isolated samples of the EIA virus.

At the same time, with regard to the structural proteins of the predominant proteins in lentivirus up to 90% of the protein structure is codified by the gag gene, of which the p26 protein is the largest protein in the viral core. It is highly conserved in all isolated samples of the Equine Infectious Anaemia virus in the world. As such, all diagnostic tests are based on detection of antibodies for the p26 protein.

p26 is more antigenically stable in isolated EIAV than gp45 and gp90 glycoproteins (OIE Terrestrial Manual 2013 Chapter 2.5.6-2.1.1) and the one used in commercial diagnosis reagents.

While the ELISA can detect antibodies slightly earlier and in smaller concentrations than the AGID, a positive test result by ELISA should be retested using the AGID test to confirm the diagnosis because some false-positive results have been noted with the ELISA, which do not occur in immunodiffusion procedures because of the specificity of the identity reaction (OIE Terrestrial Manual 2013 Chapter 2.5.6, page 2).

Contact Form

Contact us



Rua Monsenhor Alfredo Pereira Sampaio, 420
Vila São Pedro – São Paulo – SP – Brasil

(55 11) 5631-2768
(55 11) 5631-2838
Fax 55 11 5631-2814