What is Heat Stroke?
Your horse’s body can become overheated as a result of high temperatures or due to high intensity exercise, where heat production can increase by up to 50%. Should this occur, it can impact his respiratory, vascular, nervous and muscular systems. It is imperative that the body temperature of your horse be cooled down and that lost fluids are replaced so that these systems will not stop working, and cause your horse’s body to shut down. Hot temperatures and high humidity can lead to heat stroke in horses that exercise as well as horses that don’t exercise.
Resulting from becoming significantly overheated, heat stroke can lead to the respiratory, vascular, nervous and muscular systems of a horse to stop working, causing his body to shut down.
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Symptoms of Heat Stroke in Horses
Heat stroke may start as dehydration or heat exhaustion, with heat stroke rapidly following. It is important to understand the symptoms of heat exhaustion so that you can assist your horse before his condition worsens. Symptoms include:
- Significant sweating
- Increased heart rate (greater than 60 beats per minute)
- Rapid breathing (greater than 80 breaths per minute)
- Significantly fatigued
- A rectal temperature of more than 104 degrees
- Eyes appear sunken and facial expression dull
- Lack of urination
- Convulsions and collapse
Should your horse’s condition worsen and he develops heat stroke, the following signs may be present:
- A fever greater than 106 degrees
- Skin feels dry and warm
- Signs of issues with the central nervous system
- Weaving and walking unsteadily
- Falling down and struggling to get up
- Lack of awareness of their surroundings
- Kidney or liver failure
- Stomach pain
- Swelling in the lungs
- Sudden respiratory difficulties
Your horse may initially experience heat stress or dehydration. If unresolved, his condition may progress to heat exhaustion and ultimately heat stroke.
Causes of Heat Stroke in Horses
Heat stroke occurs as a result of hot and humid weather, along with intense exercise. Overweight and out of shape horses will be more likely to develop heat stroke. If your horse is not exercising, he can develop heat stroke when spending time in an enclosed trailer, an area with no shade, or when in a barn that is closed or not well ventilated. Horses that have an inability to sweat are also more likely to develop heat stroke.
Due to his large muscle mass, your horse is able to develop a great deal of heat and when temperatures are high, he will struggle to cool off. When your horse becomes overheated, he loses a lot of water and electrolytes as a result of his sweating. As he sweats more, his body fluids and electrolytes become more imbalanced and his respiratory rate increases in an effort to release his increased heat. As he struggles to keep up with the increasing heat, your horse may become dehydrated.
Should your horse be unable to cool down, his nervous and muscular systems will stop their normal function; once this happens, heat stroke is likely unless you are able to cool your horse down and replenish fluids lost through sweating.
Diagnosis of Heat Stroke in Horses
If you suspect that your horse is suffering from heat stroke, you will want to contact your veterinarian immediately. While you wait for your horse to be examined, immediately begin trying to cool him and his environment. Your veterinarian will be able to diagnose heat exhaustion or heat stroke through examining your horse. In addition, your veterinarian will seek more information from you regarding his activity and where he had been spending time, as well as the symptoms you have noticed and how long you have noticed them.
Treatment of Heat Stroke in Horses
Should your horse experience heat exhaustion or heat stroke, it is important that the condition be determined quickly and aggressive treatment begun immediately. Even if symptoms are initially minimal, you will want to move your horse to a shady area and have a fan blowing on him. Once he is in a cooler location, using a sponge or a hose you can put cool water on his neck and body, focusing on the large veins of his neck and the thin-skinned parts in the groin. Rubbing alcohol can be used on the back and neck areas in order to help him cool down. Upon stabilizing, you can offer your horse small quantities of cool water. Should your horse be unwilling to drink or if he is dehydrated, intravenous fluids should be administered to help replace lost fluid and balance electrolytes.
There is some debate as to whether antipyretic, anti-inflammatory drugs should be used. While these drugs can protect your horse from heat shock proteins and relieve pain, they may not help to lower the body temperature in a horse with heat exhaustion or heat stroke. Usually at least one dose should be given to the horse. Sedatives may be helpful for horses that are agitated and are showing neurological symptoms. Glucocorticoids like methylprednisolone sodium succinate should be administered intravenously if your horse has severe heat stroke and is showing quickly progressing neurologic symptoms in order to prevent shock and forestall organ system failure. Any other treatment considered will depend upon the symptoms that your horse is experiencing.
Recovery of Heat Stroke in Horses
Your horse’s prognosis will depend on how severe his condition is. You will want to follow the recommendations of your veterinarian in order to ensure the best outcome for your horse. Your veterinarian will likely want to conduct blood work in order to determine if there are any liver or kidney problems and depending on the results may repeat the tests. It is important that a horse who has experienced heat stroke get plenty of rest, not exercising at all for a minimum of three to five days. Should your horse have experienced heat exhaustion or heat stroke, he may be more likely to experience the condition again, meaning he should be watched closely when exercising or staying in an enclosed space in high temperatures.