Equine Fescue Edema: Signs, Symptoms and Causes

The perennial tall fescue grass has caused horses in Australia to come down with a toxic condition called equine fescue edema. Australian scientists have noted that horses who grazed pastures with Mediterranean varieties of tall fescue grass have been affected by this condition. This type of tall fescue grass has bacteria and fungi that lives inside of it. These bacteria and fungi, called endophytes, are ingested by a horse when grazing. Unfortunately, horses that are affected will need to get help from a veterinarian immediately. Failing to do so can be fatal to the horse because of the high toxicity they are exposed to.

Horses who have grazed on other types of fescue grasses have not had the toxins transfer into their system. This can cause a state of panic and confusion among horse owners and needs to be addressed immediately. Those who are concerned about equine fescue edema will need to categorize all of the grass and plants that are in their pastures. Knowing the exact types will help determine the chance of a horse being affected. The tall fescue grass acts as a natural deterrent to pests and will grow freely. This causes the tall fescue grass to be very abundant. This makes it very hard for owners to ensure that their pastures are cleared of this strain of grass.

The origins of equine fescue edema are quite interesting. The condition was first seen in 2007, when many horses became ill after an intense drought. The drought lasted for a number of seasons and the tall fescue grass remained. The drought ended when massive amounts of rain fell in the region. The rains were quite intense and only lasted for a very short period of time. Soon after the rains, horses started to show signs of illness. The common symptoms were: swelling of the abdomen, swelling of the neck, swelling of the head, swelling of the chest, reduced appetite and unusual moods. Many horses died from the issue, while some horses survived. Some of the horses that survived experienced reproductive issues and others did not.

Equine fescue edema is a rather concerning illness because the swelling associated with it is very difficult to notice. Horse owners will not always be able to observe the swelling without the horse undergoing tests from a veterinarian. The swelling is thought to be caused by a drop of protein levels in the horse’s blood.

The bacteria, endophyte or fungus known as Max Q or Max P is not present in all of the Mediterranean tall fescue grasses. The grasses which contain Max Q or Max P will be the main concern for horse owners as they are the cause for the toxic chemical reaction that occurs. Thankfully, symptoms of equine fescue edema are noticeable in just one week and horses can be treated quickly. Moving a horse to another pasture which does not contain this strain of Mediterranean tall fescue will typically aid in the horse’s recovery. However, if a horse is affected by equine fescue edema, they should always be treated by a professional.