Have you noticed a change in the temperature this past month? If you’ve either spent any time outside or if you’ve watched the news lately, you’re probably aware that there have been many heat waves recently.

This past Friday, France experienced its hottest day in history, when temperatures reached 113 degrees Fahrenheit. ⁽²⁾ And France was not the only European country affected by this heat wave. According to NPR, “record temperatures gripped other parts of Europe this week.

Heat records were broken in Germany, Poland, the Czech Republic, Switzerland, Luxembourg and the small principality of Andorra, between France and Spain.” ⁽²⁾ The United States was not immune to these increased temperatures, either. Earlier in June the New York Times reported, “ blistering temperatures in cities like Las Vegas (102 degrees), Sacramento (103) and Phoenix (109).” ⁽¹⁾

Thankfully, there is a lot of good advice out there about how to people and dogs safe during heat waves - such as in this NBC Article. However, it’s important to also remember our equine friends during heat waves.

Unlike dogs, horses sweat to dissipate heat and regulate body temperatures. Dr. David Ramey informs us that, “when horses don’t sweat normally they essentially can’t cool off at all.  If they can’t cool off, it can lead to overheating and sometimes to heatstroke. Heatstroke is a potentially fatal condition.” ⁽⁵⁾

So, If you are a vet tech working with equine patients or a horse owner or both, you’ll always want to check to make sure horses are sweating normally, especially during heat waves. If they are not sweating or only partially or minimally sweating, they could be suffering from anhidrosis, which is defined by Dr. Martha Mallicote as, “a compromised ability to sweat.”⁽⁴⁾

The cause of anhidrosis is still being investigated so currently, the treatment is via careful husbandry and supportive care measures. According to Dr. Mallicote, the most successful approach is to relocate horses to cooler climates.

However, if this is not possible, some recommended husbandry and management changes include: 

“Keep non sweaters stalled or in a shaded paddock during the day. Provide access to fans, misters or sprinklers to help keep them cool.

Some horses will step into troughs or ponds in their pastures to cool off.

They should have constant access to cool, clean drinking water. Adjunctive or preventive (before hot weather hits) feeding of electrolytes or salt mixtures (“Lite Salt”) might help the horse maintain appropriate electrolyte concentrations.” ⁽⁴⁾

While it’s important to make sure you don’t have a nonsweater during any hot time of the year, in light of recent waves, it’s important to keep an even closer eye out for this condition. Additionally, all horses should be monitored for signs of overheating.

If you notice that a horse is breathing rapidly, has a high temperature or other clinical signs such as depression or decreased water intake or appetite, it is advisable to begin some careful cooling measures and alert a veterinarian immediately. ⁽³⁾

References:

1. Bogel-Burroughs, Nicholas. California Heat Wave: Why It’s 100 Degrees in San Francisco in June. New York Times. 
2. Ingber, Sasha. France Suffers Through Hottest Day in its History - 113 Fahrenheit. NPR. 
3. Judd, Bob. Anhidrosis in Horses. VeterinaryPartner.com. 
4. Mallicote, Martha. Understanding Anhidrosis. AAEP. 
5. Ramey, Dave. Anhidrosis. David Ramey, DVM.