Dawson Creek Veterinary Clinic
238-116 Ave
Dawson Creek, BC V1G 3C8
(250) 782-1080
Dr. Zoë Ross, Dr. Andrew Hodges
Dr. Mike Ross, Dr. Cathy Saker
Dr. Heather Weaver, Dr. Sandy Jameson
“Swamp Fever” in Horses
“Swamp Fever” properly known as Equine Infectious Anemia is a disease we commonly have questions about. Many people have had to have their horses “Coggins” tested by a veterinarian at some point either because they have been travelling to the USA or because they are taking their horse to a show or clinic that requires this test to be done.
This disease is caused by a virus and it affects horses, donkeys and mules. The virus reproduces in the horse’s blood cells and circulates through their body in the bloodstream. The horse’s immune system will respond to this infection by attacking and destroying its own blood cells. This can lead to anemia (low red blood cell count) and also organ damage from the inflammation caused by this attack. Some horses can carry this virus for their entire life and not show any clinical signs. Others will show symptoms such as a fever, anorexia (not eating), depression, swelling on their legs and the underside of their belly, muscle weakness and wasting, jaundice (yellow color) of their mucus membranes (gums,etc) and infertility.
- There are three phases of the disease and every case is slightly different in how the horse reacts to the infection:
- Acute – this is when the infection is at its worst and there are large numbers of virus circulating in the bloodstream. Horses are very ill.
- Chronic – there are large numbers of the virus circulating in the bloodstream. Horses may alternate between being very ill and appearing normal.
- Inapparent Carrier – the horse is carrying the virus but doesn’t appear ill.
This disease is a blood borne disease. It is spread by biting insects – mainly horseflies and deerflies. It can also be spread through needles and medical equipment that is contaminated with blood. This disease cannot be spread by horses simply being in contact with each other. In this area, we occasionally find animals that have this disease. The animals that seem to be in the biggest risk category are those that are in close proximity to other horses and are in areas with large numbers of biting insects.
There is no treatment or cure for this disease. There is also no vaccine for the disease. Because of its infectious nature and the fact that it can’t be treated, this disease is currently a reportable disease under the Health of Animal’s Act. A simple blood test that identifies antibodies against the virus can be done to test for this disease. This is called a “Coggins Test” and generally takes anywhere from 6-10 days from the time the sample is taken until the time the final results are available. Horses cannot be taken into the USA without a negative Coggins test within the previous 6 months and an export inspection by an accredited veterinarian with the previous 30 days. Many public and private stables, trainers and facilities require that horses be tested negative prior to entry into the facility.
If a horse is tested and the test comes back as a positive, the Canadian Food Inspection Agency is notified. The horse is then retested and several different types of tests are done on the blood to confirm that the horse is definitely positive. It is recommended that animals that test positive are humanely euthanized, however the owner of the infected animal may choose to house the horse in a permanent quarantine. More information on this is available through a federal district veterinarian (the CFIA).
This can be a very damaging and deadly disease and it is important that horse (and mule and donkey) owners are aware of its existence. Testing, insect control, using one disposable needle and syringe/ animal rather than reusing needles, and proper disinfection of any medical equipment is essential in its control.