Equine sweating and anhidrosis
Part 2: anhidrosis

Abstract

The condition of anhidrosis is described in this review, and the latest theories on the causal factors are explored. The evidence supports the hypothesis that anhidrosis is an inappropriate response to prolonged climatic stress (generally combined heat and high humidity), which can be evoked in a small (approximately 10 +/- 5%) proportion of the equine population. It is caused by gradual failure of the glandular secretory cell processes, initiated by desensitization and subsequent down-regulation of the cell receptors as a result of continued adrenaline-driven hyperactivity. It progresses through secretory failure and culminates in gradual, probably irreversible, glandular dedifferentiation and ultimate degeneration. There is a need for considerably more research on the secretory and transcriptional processes to document the changes arising within the glandular secretory mechanism as a prelude to development of a corrective treatment.

Evaluation of clinical and reproductive parameters in Mangalarga Marchador mares treated with different doses of Cloprostenol or Dinoprost

“…In horses, this clinical sign is due to adrenoreceptor stimulation of sudoriparous gland cells, determined by a significant increase in adrenalin and noradrenalin concentrations after prostaglandin administration (Jenkinson et al, 2006(Jenkinson et al, /2007. In general, sweating gradually increases due to increasing doses (Miller et al, 1976;Irvine et al, 2002;Kuhl et al, 2016ab).…”

A review of anhidrosis in horses

“…; Jenkinson et al . ). Although receptor downregulation presumably is involved, there was also evidence that long‐term activation of phosphodiesterase (an enzyme that removes cAMP) may play a role in desensitisation.…”

“…At the ‘far end’ of the sweating process, obstruction of excretory ducts by debris plugs also is a result of nonsweating and cellular degeneration rather than a cause (Jenkinson et al . ).…”

Clinical Approach to Commonly Encountered Problems

“…[16][17][18] This condition occurs primarily in horses living in hot, humid environments and has been documented in about 2% to 6% of horses living in Florida. Anhidrosis is an inappropriate response to prolonged climatic stress characterized by a partial or total loss of the ability to sweat.…”

“…Many causes of hyperthermia, such as exercise-related hyperthermia and malignant hyperthermia, can be distinguished from fever based largely on the signalment and history of the patient. 18,67 Genetic testing is available for detection of the RyR1 mutation in cases of suspect malignant hyperthermia. 14 Treatment with macrolide antibiotics is significant due to the potential for macrolides to cause hyperthermia.…”