Genetic Health Risks: Chronic Idiopathic Anhidrosis

Summer is upon us which means long sunny days, high temperatures, and no shortage of sweat - unless your horse has anhidrosis. Also known as a “non-sweater,” horses with anhidrosis sweat less than normal horses or not at all, even in hot weather or during exercise. Horses diagnosed with Chronic Idiopathic Anhidrosis (CIA) have a history of not sweating without an obvious cause. While we may not entirely know the reason why some horses develop CIA and others do not, we do know that there is a genetic risk factor associated with horses developing CIA that you can test for with Etalon Equine Genetics. And it’s definitely worth testing for! Of the horses we have tested for the CIA genetic risk variant, about 50% have at least one copy of the mutation.

Key Takeaways

• Chronic Idiopathic Anhidrosis (CIA) is a health condition in which horses have a consistent history of lacking a sweat response, or stop sweating without an apparent reason. It can develop suddenly or gradually over time.

• CIA is most often observed in horses that live in hot and humid climates but has also been reported in cooler climate regions. Previous studies have shown an increased risk in Thoroughbreds and Warmbloods, but several breeds of horses are known to be affected.

• Studies have found the suspected cause of CIA is due to a genetic mutation that can result in a potassium channel failure. If a horse inherits one copy of the mutation (CIAR/n), they face a moderate risk of developing CIA, whereas if they inherit two copies (CIAR/CIAR), there is a high risk that they may develop it. Etalon Equine Genetics has DNA testing options to determine if your horse carries the variant responsible for this increased risk.

Understanding what CIA is, how to spot it, and what to do about it are crucial to managing this potentially life-threatening condition. This includes grabbing CIA by the reins by identifying your horse’s genetic risk factor with Etalon so you can keep them healthy and happy all year long.

What is CIA?

Chronic idiopathic anhidrosis is a health condition where a horse historically, or chronically, lacks an appropriate sweat response for no apparent reason (idiopathic).

How common is CIA?

CIA is more commonly observed in specific breeds such as Thoroughbreds and Warmbloods, but it can affect a wide variety of horses. Epidemiologic studies, or studies that look for patterns and determinants of health conditions, currently estimate that CIA affects at least 2% of all horses, though this number could vary depending on climate and the quality of studies. One study performed in Florida found that horses with a family history of anhidrosis have over 21x the odds of also being affected by the condition.¹

Symptoms of CIA

Recognizing CIA symptoms is crucial for prompt diagnosis and treatment. While the most common and best-known symptom is significantly reduced to no sweating at all, other clinical signs may include:

• Increased respiratory rate
• Elevated body temperature
• Lethargy
• Poor performance

Diagnosis and Treatment

Diagnosis of CIA involves a multifaceted approach, including clinical evaluation by your veterinarian and genetic risk assessment through DNA testing.

Diagnosis:

Clinical Evaluation: A veterinarian will conduct a detailed history and physical examination to identify symptoms.

Genetic Testing: Testing for the CIA genetic variant can confirm the presence of the mutation responsible for increased risk. This test does not determine if your horse has CIA, but rather evaluates if they are genetically predisposed to an increased risk of developing the condition.

Treatment:

Supportive Care: Focuses on stabilizing the horse, maintaining hydration, and managing body temperature.

Environmental Management: Providing shade, fans, and frequent hosing with water to keep the horse cool.

Genetic Risk Factors

Some horse breeds and those with a family history of anhidrosis are more likely to experience this condition, suggesting that it might be inherited. To explore this, researchers studied the genetic makeup of 200 horses, focusing on those with chronic anhidrosis. They discovered that a specific region in the KCNE4 gene might be linked to this condition.² This gene is responsible for part of a potassium channel protein, which plays a role in how a horse’s sweat glands operate.

A particular mutation in the KCNE4 gene could be disrupting this protein, potentially explaining why some horses develop anhidrosis. However, more research is needed to confirm this connection in larger groups of horses. This study suggests that issues with ion channels might be a key factor in the inability to sweat properly, possibly making anhidrosis a form of congenital channelopathy.

Knowing whether a horse carries this genetic risk factor can help horse owners and veterinarians protect a horse's health by taking extra precautions to avoid exposure to overly hot and humid environments or situations that increase the horse’s chances of overheating.

Testing and Understanding CIA Risk

Testing for this genetic variant with Etalon is included in our Pro Package and Health Panel, providing horse owners with valuable information about their horse's susceptibility to developing CIA. Results may indicate higher or lower risk of developing CIA based on the presence or absence of the risk variants.

CIAR/CIAR = homozygous for Chronic Idiopathic Anhidrosis Risk, high risk

CIAR/n = heterozygous for Chronic Idiopathic Anhidrosis Risk, moderate risk

n/n = no variant detected

It is important to note that if your horse carries one or two copies of the CIA risk variant, it does not mean that your horse has or will definitely develop CIA! What it does mean, however, is that they may be more likely to develop CIA depending on how many variants they carry. Knowing your horse’s genetic CIA risk level lets you make proactive management decisions to make sure your horse stays safe in the heat and during exercise.

Prognosis

The prognosis for a horse with chronic idiopathic anhidrosis can vary depending on the severity of the condition and how well it is managed. Anhidrosis, the inability to sweat properly, is particularly concerning because sweating is the primary way horses dissipate heat. Without the ability to cool down through sweating, a horse is at high risk for overheating, especially in hot and humid climates.

Prognosis Factors:

Severity: Horses with mild cases of anhidrosis may manage with careful monitoring, lifestyle adjustments, and avoiding heat stress. However, severe cases can lead to life-threatening hyperthermia if not properly managed.

Management: Horses with chronic anhidrosis require careful management, including keeping them in cooler environments, providing fans or air conditioning, avoiding exercise during the hottest parts of the day, and ensuring access to plenty of clean, fresh water. Some horses may also benefit from supplements or treatments aimed at supporting their condition, though these can have varying degrees of success.

Long-Term Outlook: Over time, chronic anhidrosis can become more difficult to manage, especially in climates where heat and humidity are persistent and unavoidable. The horse's performance and quality of life may be significantly affected, and in some cases, owners may need to consider relocating the horse to a cooler climate or reducing the horse's activity level.

Complications: If the condition is not managed effectively, the horse can suffer from repeated episodes of overheating, which can lead to organ damage, collapse, or even death.

In summary, the prognosis for a horse with chronic idiopathic anhidrosis is guarded, and the long-term outlook heavily depends on the severity of the condition and the ability to manage the horse’s environment and activity level.

Prevention

Preventing chronic idiopathic anhidrosis in horses can be challenging because the exact cause of the condition is not fully understood, and it may have genetic components. However, there are several strategies that can help minimize the risk or manage the condition if a horse is predisposed to anhidrosis:

Avoid Extreme Heat: Keep horses in cooler, less humid environments whenever possible. This may involve providing shade, fans, or even air-conditioned spaces during hot weather.

Time Activity Wisely: Exercise horses during cooler parts of the day, such as early morning or late evening, to avoid peak heat and humidity.

Maintain Hydration: Ensure horses have constant access to clean, fresh water to support their ability to regulate body temperature.

Electrolyte Balance: Provide electrolytes, especially in hot weather, to support sweating and overall hydration. Proper electrolyte balance can be crucial for horses that are prone to anhidrosis.

Environmental Cooling Strategies: Use fans or misters to keep horses cool, especially in barns or stalls that can become hot and stuffy. You can also hose down a hot horse with cool water during stretches of hot weather and/or after strenuous exercise to help them regulate their body temperature.

Regular Monitoring and Early Intervention: Monitor your horse’s vital signs, especially during hot weather, to catch early signs of anhidrosis or overheating. If a horse starts showing signs of reduced sweating, take immediate steps to cool them down and consult with a veterinarian to discuss potential treatments or supplements that may help. You can learn how to measure your horse’s vital signs here!

Breeding Decisions: If the horse’s relatives have a history of anhidrosis, consider this when making breeding decisions. Avoid breeding horses with a known history of anhidrosis to reduce the chances of passing the condition to offspring.

Supplements: Some horses may benefit from specific supplements designed to support sweating, though the effectiveness of these can vary.

While it is not always possible to prevent CIA altogether, especially in genetically predisposed horses, careful management of the horse’s environment, hydration, and activity levels can help minimize the risk and manage the condition if it develops. Early intervention and continuous monitoring are key to keeping affected horses comfortable and safe.

Conclusion

Chronic idiopathic anhidrosis poses a serious risk to horse health and well-being, but ongoing research and advancements in genetic testing are constantly providing us with new avenues for understanding and managing CIA and other health conditions. Knowing your horse down to the DNA, including their genetic predisposition for an increased anhidrosis risk, allows you to make informed decisions about their care and environment. By combining this knowledge with proactive management strategies, you can take significant steps to protect your horses from the challenges associated with CIA, ensuring their health and safety no matter the weather.

References

¹ Johnson, E. B., Mackay, R. J., & Hernandez, J. A. (2010). An epidemiologic study of anhidrosis in horses in Florida. Journal of the American Veterinary Medical Association, 236(10), 1091–1097. https://doi.org/10.2460/javma.236.10.1091

² Patterson Rosa, L., Walker, N., Mallicote, M., MacKay, R. J., & Brooks, S. A. (2021). Genomic Association of Chronic Idiopathic Anhidrosis to a Potassium Channel Subunit in a Large Animal Model. The Journal of investigative dermatology, 141(11), 2639–2645.e3. https://doi.org/10.1016/j.jid.2021.05.014