Advice for horse keepers on Equine Infectious Anaemia
Equine Infectious Anaemia
Animal Health investigates all incidents of suspected notifiable disease. If you suspect signs
of equine infectious anaemia, you must immediately notify your local Animal Health office.
THE RISK TO YOUR ANIMALS
Equine Infectious Anaemia (EIA) is a viral disease that affects horses, mules and donkeys, spread by
biting flies.
Horses are most likely to become infected when travelling abroad to countries, or areas of countries,
where the disease is endemic, or from the use of biological products infected with the EIA virus. EIA is
often fatal to horses. If the affected animal recovers it remains a lifelong carrier of the disease and will
thereby be infectious to other animals, therefore all infected animals must be humanely destroyed to
control the spread of disease.
HOW TO RECOGNISE THE DISEASE
What to look for
Animals may be affected acutely, chronically, or sub-clinically. The incubation period is variable, from
a matter of days to a few months, but is generally one to three weeks.
All infected animals become carriers of the disease and are infectious for life.
The disease is characterised by:

a recurring fever

anaemia

oedema

emaciation and
death
Clinical signs of the disease are however often not apparent, and keepers of such animals are
unlikely to realise that they are infected unless blood testing is carried out.
REDUCING THE RISK OF DISEASE
This virus is normally transmitted through large biting flies such as horseflies (tabanid species) or
stable flies (Stomoxys calcitrans). Transmission of the disease may occur where there are adult flies
of this type in proximity to infected horses. The adult flies are only active between May and
September, with activity peaking in July-August. The flies overwinter as larvae and the larvae cannot
transmit the disease. In addition, the flies normally travel no more than 200m to feed and are not likely
to be moved long distances by wind, therefore infected flies do not spread far from the point of an
infected horse. EIA is not spread by smaller flying insects such as midges and mosquitoes under
normal conditions.
It is possible for disease to be transmitted by equipment that is contaminated, especially if this
contamination is with blood, mile or maternal/placental fluid. Relevant equipment could include
veterinary instruments, e.g. needles and scalpels, dental, obstetric grooming, tattooing, farriery and
tack such as bridles. Good hygiene practices will reduced the risk of transmission by these routes to
negligible.
EIA may also be spread by saliva, nasal secretions, faeces, semen, ova and embryos. However, the
risk from these routes is low and can be mitigated by good hygiene measures.
Pregnant mares may pass the disease to their foals in the womb.
REDUCING THE IMPACT OF DISEASE
As a disease control measure, animals testing positive for EIA must be humanely destroyed. This is
necessary for the welfare of the affected horse, but also to protect other horses from infection, as
once infected, horses are infected for life and continue to pose a risk to other horses in close
proximity.
Only animals that have tested positive for EIA will be destroyed; animals are not culled on suspicion.
In addition, each animal that has been traced as a contact with infected animals will be kept under
restrictions and tested until we are satisfied that it is not affected by the disease. Restrictions will be
lifted when a veterinary risk assessment advises that the risk is low.
Further information

Code of Practice
for Equine
Infectious Anaemia
(PDF - on the
Horserace Betting
Levy Board
website)
The latest news on Equine Infectious Anaemia from the Defra website