All you need to know about Swamp Fever

A horse in Cornwall has been put down after it was confirmed that it had the rare and contagious disease Swamp Fever. The Department of Environment, Food and Rural Affairs (DEFRA) said the animal tested positive for Equine Infectious Anaemia (EIA) and all the other horses on the yard have been put into quarantine.

Equine Infectious Anaemia, is also known as EIA or Swamp Fever. 

It affects all Equidae and is caused by a lentivirus, which is just like  Human Immunodeficiency Virus (HIV), affects the immune system of the horse. Interestingly, also like HIV, it can be transmitted through blood, saliva, milk and bodily secretions.

It is primarily spread via biting flies and can survive up for 4 hours in the carrier (ie. the fly) so can spread quite quickly amongst a herd.

Contaminated surgical equipment, recycled needles and syringes and bits can also cause the disease to spread. Mare's can transmit the disease to their unborn foals via the placenta.

Signs and Symptoms
Swamp fever can take on Acute, Sub-Acute, Chronic or Sub-Clinical (infected, but showing no signs) forms. It is a virtual death sentence for the horse, as the disease is usually so severe that it kills the horse. If the horse does recover it will be compulsory euthanised to avoid spreading the disease. According to the Indiana State Board of Animal Health, between 30 - 50% of horses infected with swamp fever die within 2 - 4 weeks of showing initial symptoms.

  • Acute: The acute form is a sudden onset of the disease at full force. Symptoms include a high fever, anaemia (due to the breakdown of red blood cells), weakness, swelling of the lower abdomen and legs, weak pulse and irregular heartbeat. The horse may spontaneously die. 
  • Sub-Acute: A slower, less severe form of the disease. Symptoms include recurrent fever, weight loss, an enlarged spleen (which can be felt during a rectal examination), anaemia, and swelling of the lower chest, abdominal wall, penile sheath, scrotum and legs.
  • Chronic: The horse tires easily and is unsuitable for work. It may have recurrent fever and anaemia. It mute or nay relapse to the sub-acute or acute form even several years after the original attack. 

The Coggins Test is a test for swamp fever developed during the 1970's and is said to be approximately 95% accurate. A negative Coggins test proves that the horse is safe to have around other healthy horses. 

To determine if a horse is negative or positive for swamp fever a blood sample is taken and tested for the presence of swamp fever antibodies. Antibodies are proteins that are produced by the immune system that help recognise and fight infections or other foreign substances in the body. The antibody recognises the swamp fever virus and attempts to fight it off. 

Prevention and Treatment
Currently, there are no vaccines on the market to protect a horse from swamp fever. There is also no treatment for those affected - horses who test positive for swamp fever are compulsory euthanised.  

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