Equine Infectious Anaemia Virus

Equine Infectious Anaemia Virus (‘EIA’ or Swamp Fever) has been found in Devon in September 2010.

What is ‘Swamp Fever’?
This virus only affects equines although similar virus species affect other animals or humans. This ‘Lentivirus’ differs from those in other species in that it’s clinical signs are sometimes rapid in onset compared to e.g. the Human immunodeficiency virus that has a chronic progressive course.
Horses are infected by a variety of means but exposure to blood from another infected equine usually vector borne by biting flies (e.g. Horse flies or  Stable flies) is the usual route of transmission. Infected blood products or blood contaminated equipment ( syringes, needles, tooth rasps) can also transmit the disease.
In the current outbreak in Devon disease was found in a horse imported 2 years ago from Romania. This horse was humanely euthanased and the other 2 horses on the premises have been blood sampled to test for the disease.
So what are Defra/ Animal Health doing?
The basis of control is to quarantine all horses in contact with known infected cases and blood test them to show whether they are infected. THERE IS NO CURE and treatment is aimed at supporting the individual until it is confirmed as infected. If infected all horses are likely to be euthanased . At first this may seem draconian but many infected horses will die despite treatment and all survivors are permanent carriers and reservoirs of infection for future outbreaks.

Clinical signs
Horses suffer repeated disease incidents with progressive loss of condition, anaemia, muscle weakness, severe depression, fever, anorexia, ataxia, jaundice and swelling of the head, trunk and limbs which may kill them at a future date.

We have a long wait to see if the outbreak has been controlled because although most cases show a blood antibody rise in 7-14 days after infection some do not and antibodies may take 30 + days to show. Hence repeated negative blood tests are needed; which will mean waiting for 3 months plus before we can breathe a huge sigh of relief.

There is no need to panic yet but if you suspect a problem contact Defra.

Useful other sources of information.
http://www.thehra.org/doc.php?id=42413
http://www.defra.gov.uk/foodfarm/farmanimal/diseases/atoz/eia/about/index.htm