A decade ago, the state Legislature passed a law requiring that equines be tested for equine infectious anemia (EIA). This was a standard practice throughout the country as states tried to manage this potentially fatal horse disease.
Now, after the law requiring testing for EIA expired on Jan. 1, Gov. Rick Snyder has signed into law House Bill 4567, which re-enacts the same provisions as the expired statute requiring EIA testing for horses.
One major difference is that the test for EIA has to be conducted at least once within every 12 months, as opposed to the calendar year in order to give owners more leeway.
“The problem with this disease is that some horses had it but showed no signs of illness, so the only way to find out if they were ill was to require testing,” said Dr. Steve Halstead, the state veterinarian with the Michigan Department of Agriculture and Rural Department (MDARD).
The EIA virus only affects horses and is closely related to the human AIDS virus. The virus causes the immune system to attack red blood cells making the horse severely anemic.
EIA has three degrees of infectiousness: acute, chronic, and inapparent. Those in the acute stage may die within two or three weeks, while horses in the chronic stage may recover and go through undulations of the illness until they eventually wear out and die or are recognized as ill and are euthanized. Those in the inapparent stage are carriers of the disease but show no manifestation of symptoms and are therefore the most problematic.
One means of spreading the disease is through using the same needle between an infected horse and another. However, the predominant vector is flies. Mosquitoes are not vectors because they cannot transport enough fresh blood between horses.
Flies, however, are not reservoirs for the disease, according to Halstead.
“The virus has to be transferred within a few minutes as it can only be spread through the fresh blood of an infected horse. Therefore, it can only be spread a short distance and has a maximum range. It’s easily controlled and could be eradicated, but we have to find all the horses that are infected,” he said.
Many states have passed laws requiring that horses be tested once every 12 months if they are to be participating in activities where they will be in close proximity to other horses to prevent the spread of the disease. This also applies to horses that are being moved from state to state and those that have changed ownership.
According to Halstead, the testing laws have been “very successful” in helping contain the disease.
“In the first couple years, we removed 50 horses from the population so that they could no longer be a threat to other horses. Within a few years, we have had no new cases. The industry has been very much behind these measures. Testing horses before they participate in a fair or show to make sure they are healthy reassures other owners that the other horse in the next stall has been tested. It also provides reassurance in horse sales, as well.”
Michigan’s law requiring horses to be tested at least once in the calendar year before entering exhibitions, changing ownership, or entering Michigan from another state expired at the beginning of this year.
There is no cure or vaccine for the virus. Therefore, the only options for a positively-tested horse are euthanasia or quarantine, which has to be at least a quarter of a mile away from other horses.
“It’s not a good day when you learn that your horse tested positive for EIA,” Halstead said.