ISSN 2398-2977      

Equine infectious anemia virus

pequis

Synonym(s): EIA virus, EIAV


Introduction

Classification

Taxonomy

  • Family: Retroviridae.
  • Subfamily: Lentivirinae.

Active Forms

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Clinical Effects

Epidemiology

Habitat

  • Reservoirs: horses, donkeys   Donkey  and mules   Mule  .
  • Infectious virus present in blood, milk and semen.

Transmission

  • Mechanical inoculation of blood by hematogenous insects eg deer and stable flies, or by hypodermic needles.
  • Transmission at mating (infrequent).
  • Vertical transmission via milk (not via placenta).
  • Transplacental transmission can occur, especially if acute infection occurs during pregnancy.

Pathological effects

  • Infected animals develop long-lasting antibody titers.
  • Antigenic variation allows virus to evade host immune response to form relapsing clinical signs.
  • Immune complexes of virus and antibody become deposited on erythrocytes, endothelial cells and renal glomeruli   →   complement activation   →   inflammation and hemolysis.
  • Equine infectious anemia   Equine infectious anemia (EIA)  has a variable presentation.
  • Disease is generally less severe in donkeys than in horses.

Acute EIA

  • Massive viral replication   →   destruction of infected macrophages   →   acute hemolytic disease 7-10 days post-infection   →   widespread hemorrhage and necrosis of tissues.
  • Often fatal.

Subacute EIA

  • Animal recovers from acute symptoms   →   2-4 weeks   →   subsequent hemolytic crisis   →   weakness, edema, petechiation, anemia, icterus and ataxia .
  • Cycle may recur, or disease may be fatal.

Chronic EIA - 'Swamp Fever'

  • Relapsing cycles of pyrexia, weight loss, anemia, and icterus.
  • Thrombocytopenia occurs during viremic episodes; may manifest as petechie, bleeding.
  • Can recur several times, usually within the first year post-infection.
  • Becomes chronic carrier of the virus.
  • Hemagglutining glycoproteins interact with antibodies and complement   →   hemolysis and erythrophagocytosis, plus decreased erythropoeisis and serum iron   →   chronic anemia   Anemia: chronic disease  .

Subclinical EIA

  • Probably follows an unobserved febrile episode.
  • Chronic virus carriage.

Other Host Effects

  • Virus may be carried by asymptomatic horses for many years.

Control

Control via animal

  • Supportive therapy.
  • Isolation of carrier animals.
  • Avoid re-use of needles.
  • Test blood donors.
  • Do not mate infected stallions with seronegative mares.
  • Isolate foals from carrier mares before suckling.

Control via chemotherapies

  • Isoprinosine or ribovirine have been suggested. No experimental data available.

Control via environment

  • Stable horses in fly-proof environment.

Vaccination

  • None available.

Other countermeasures

  • Import restrictions; testing of horses within and from USA.

Diagnosis

This article is available in full to registered subscribers

Sign up now to obtain ten tokens to view any ten Vetlexicon articles, images, sounds or videos, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Burki F, Rossmanith W & Rossmanith E (1992) Equine lentivirus, comparative studies on 4 serologic tests for the diagnosis of equine infectious anemia. Vet Microbiol 33 (1-4), 353-360.
  • Cheevers W P & McGuire T C (1985) Equine infectious anemia virus - immunopathogenesis and persistence. Rev Infect Dis 7, 83 PubMed.

Other sources of information

  • Horserace Betting Levy Board (2016) Codes of Practice. 5th Floor, 21 Bloomsbury Street, London WC1B 3HF, UK. Tel: +44 (0)207 333 0043; Fax: +44 (0)207 333 0041; Email: enquiries@hblb.org.uk; Website: http://codes.hblb.org.uk.

Can’t find what you’re looking for?

We have an ever growing content library on Vetlexicon so if you ever find we haven't covered something that you need please fill in the form below and let us know!

 
 
 
 

To show you are not a Bot please can you enter the number showing adjacent to this field

 Security code