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Diseases - Equine Infectious Anaemia

Equine infectious anaemia (EIA or swamp fever) affects horses, donkeys, mules, zebras and other equidae. It is a retrovirus commonly transmitted by blood-sucking insects but can be transmitted through the use of contaminated blood or blood products, instruments or needles. It does not affect humans but is a notifiable disease. That means if you suspect it, you must tell the Animal and Plant Health Agency (APHA) immediately. Failure to do so is an offence.


Current Situation

The last outbreak of EIA in Great Britain was in 2012.

This epidemiology report is a summary of the investigations by APHA to control the 2 incidents of equine infectious anaemia in Cornwall and Devon in 2012.


Clinical Signs

Some infected animals do not show signs of disease, or signs are overlooked because they don’t last for long.

Clinical signs can include:

  • recurring fever
  • tiredness, weakness and depression
  • loss of appetite and weight loss
  • frequent urination
  • diarrhoea
  • paralysis of the hindquarters
  • pinpoint bleeding beneath the tongue
  • pale mucosal membranes
  • discoloration (yellowing) of the eyes
  • rapid breathing and accelerated pulse
  • abortion in pregnant mares

Potential lifetime carriers occur because the virus persists in white blood cells. EIA can present as a recurring fever, but most progress to silent carrier states.. The most difficult animals to identify are these unapparent carriers; horses show no clinical signs associated with the infection and go undetected unless subjected to a blood test.


Biosecurity Guidance

The Government's policy on disease control is that prevention is better than cure. This approach works by reducing the chances of a disease entering the animal population, and if it does then it can be quickly spotted and dealt with through the preventative measures.

You can help prevent disease by practising strict biosecurity on your premises. Our equine biosecurity leaflet outlines practical, day-to-day actions that can be easily adopted in order to reduce the potential for the introduction or spread of disease-causing agents.


How it’s spread

EIA is most commonly transmitted by large horseflies which are usually active from May to September, with a peak in July and August. EIA can also be transmitted through blood and saliva spread through medical equipment, as well as milk, and body secretions such as semen of infected animals.

The horseflies may only travel short distances to feed, but the virus can be carried over long distances by infected horses or contaminated equipment and products.

Control Strategy

The Equine Infectious Anaemia Control Strategy describes how a case or outbreak of the disease, would be managed in Great Britain (GB).  

More information on Scotland’s disease contingency plans is available here: http://www.gov.scot/ahwcontingencyplans


There is no vaccination available for EIA. The key to prevention is the identification and restriction of infected horses.


The Specified Diseases (Notification and Slaughter) (Amendment) and Compensation (Scotland) Order 2014 provides for the relevant Minister to pay compensation for horses or equines killed for the purpose of controlling dourine (or farcy),equine infectious anaemia or glanders. The amount of compensation payable in relation to those animals is £1.


Relevant Legislation

The main domestic legislation on EIA is the Infectious Diseases of Horses Order 1987.

Other legislation relating to EIA includes: