Essential advice from vet Jo Gourlay

​This week we have a look at a condition called Equine Infectious Anaemia (EIA), also known as swamp fever, which is, thankfully, very rare in the UK but has been in the news due to a confirmed case at the start of the month in Cornwall.

EIA virus is a “lentivirus” which is part of the retrovirus family (HIV is also a lentivirus). It is a notifiable disease which means the Department for Environment, Food and Rural Affairs (DEFRA) must be informed of any suspected cases, and there is no cure or vaccine available in Europe. Although vaccines have been used internationally, they are not deemed effective or safe enough to be suitable for use within Europe.

Horses, mules and donkeys are all affected by EIA but it is not zoonotic (it cannot be transferred to humans). In Europe, the virus is most prevalent in the central and northern regions.

It is transmitted most frequently by stable flies and horse flies but less commonly can also be passed on in other ways such as contaminated instruments, needles, blood, saliva or nasal secretions.

Good hygiene will reduce the risk from many of these less likely causes. The spread of the disease is normally slow because the flies are estimated to only travel about 200 metres.

The insects are active between May and September normally with July and August being the peak within their season. Swampy type areas with woodland close by will be at highest risk, although it is not believed to be transmitted by midges or mosquitoes.

Once an animal is infected it is usually up top three weeks before the clinical signs are seen but the incubation period can be anything between days and a few months. The signs themselves can be variable, although, with the acute disease, you may expect to see recurrent episodes of fever, anaemia, emaciation, fluid retention (oedema), nose bleeds, anorexia and depression.

The condition is fatal for a number of horses and those that do survive act as carriers (so can pass on the disease to others).

In the UK, if an animal does test positive for EIA then the only course of action is for it to be humanely put to sleep. In some circumstances, this is for the welfare of the individual animal but it is also to protect others from infection.

Any animals that have been in contact with an infected horse will be kept under restrictions and tested to make sure they themselves are not infected. Although this may sound brutal, it is to ensure the welfare of all the horses with the UK as a whole and prevent the disease becoming endemic (widespread) which would result in many more deaths.

Luckily, it is very rare at the moment in the UK but if you are concerned and want to decrease the potential risk, then there is information available on the Scottish government website about biosecurity measures you can use. The DEFRA 
website also has a wealth of up to date information: go to