Koper Equine

1. Anhidrosis is the decreased ability to sweat in response to increased body temperature.
2. It is particularly problematic for performance horses, as they rely heavily on sweating for thermoregulation, with between 65-70% of body heat in horses being lost through the evaporation of sweat.
3. Humid environments, such as those found in hot climates like Florida, the Gulf Coast states, and South Carolina, decrease the efficiency of sweat evaporation and cooling, which can contribute to the occurrence of anhidrosis.
4. Horses have densely packed sweat glands, averaging 810 glands per cm².
5. Sweat glands are coiled, tubular structures with a rich blood supply and numerous nearby nerves.
6. Sweating is stimulated both by the local release of epinephrine from adrenergic nerve endings and by circulating epinephrine in the bloodstream.
7. Horse sweat contains proteins (mainly glycoproteins, surfactants, and skin defense proteins), electrolytes (sodium, potassium, chloride), and significant water.
8. Electrolyte imbalances, especially low chloride levels, are suspected to play a role in the development of anhidrosis.
9. Another likely cause of anhidrosis is the inadequate response of sweat glands to high levels of circulating epinephrine, due to habituation of the receptors.
10. Other proposed contributors include hypothyroidism, sweat duct occlusion, hormonal or metabolic imbalances, and issues with the central nervous system.
11. Anhidrosis horses typically show lower-than-normal levels of chloride excretion in their urine compared to horses without anhidrosis.
12. In chronic cases, sweat gland atrophy may occur, along with symptoms such as dry, flaky skin, hair loss, fatigue, anorexia, and decreased water consumption.
13. No specific age, sex, or color predisposition for anhidrosis has been identified. There is speculation that a genetic predisposition may play a role in anhidrosis, although no specific genetic markers have been identified.
14. Epidemiological studies indicate a prevalence of 2-6% among horses with one Florida study reporting 1.8% of horses anhidrotic and 11.2% of farms with at least one case.
15. Anhidrosis is diagnosed through clinical signs such as increased respiration and failure to cool after exercise. Though usually not necessary, confirmatory testing can be done with intradermal injections of epinephrine or terbutaline.
16. Management includes access to cool, clean drinking water, shaded areas, fans and misting fans, and regular application of cooling water.
17. Anecdotal treatments include feed supplements, dark beer, electrolytes, and thyroid supplementation, though these lack research support.
18. Prescription meds like ACTH, alpha-2 agonists, prostaglandins, antihistamines, and Methyldopa are generally considered unsuccessful.
19. Acupuncture and certain herbal medications may improve sweating in recently anhidrotic horses, though the effect is short-lived (lasts up to 4 weeks post treatment) and requires further investigation.
20. The only proven solution involves moving the horse to a cooler climate.
21. Anhidrosis can have seasonal variations, with symptoms typically worsening during the hotter months and potentially improving during cooler periods.
22. Preventive measures, such as gradually acclimating horses to hot climates, can help reduce the risk of developing anhidrosis.
23. Recent research suggests macrolide antibiotics might halt sweat production by reducing chloride transport across sweat gland cells.
24. Ongoing research focuses on chloride transport across sweat gland cells and potential treatments like macrolide antibiotics and acupuncture/herbal medicine.

More research is needed to identify specific causes, develop effective treatments, and improve our understanding of and management practices for anhidrosis.