Image0023As veterinarians we unfortunately see our share of fevers! Most fevers are short-lived, respond favorably and quickly to anti-inflammatory medications (NSAIDs), and are not entirely uncommon for this time of year, but a fever can be stressful for horse and owner alike.

Here is what you should know:
Signs of fever:

  • Not acting quite right or depression
  • Anorexia or decrease in appetite
  • Increased respiratory rate
  • Reluctance to work or lethargy

Diagnosis of fever:

  • Take temperature rectally.
  • Fever is anything >101°F
  • A complete physical by a veterinarian with careful lung exam is integral to fever examination.
  • Your veterinarian may take blood to look at red and white blood cells. The pattern of bloodwork results helps your veterinarian determine the most likely cause of fever.

Causes of fever:

  • Infection – either from bacteria, or more commonly, a virus.
  • Bacterial infections are treated with antibiotics chosen to target specific bacteria. Examples of bacterial infections include infected wounds, pneumonia, strangles (streptococcus equi), Potomac horse fever (neorickettsia risticii), Anaplasmosis (anaplasma phagocytophilum), among others.
  • Viral infections are treated through supportive care only as there are not currently effective anti-viral medications against these types of diseases. Examples of viral infections that cause fever include Eastern and Western Equine Encephalitis (EEE/WEE)*, West Nile Virus*, Rabies, Influenza (flu), and Herpes (Rhinovirus), but the vast majority of viral infections in horses are caused by a short-lived virus that only lasts 24-48 hours.
  • Inflammation – this would be less common than infection and may be caused by things that cause an overwhelming inflammatory response ex. envenomation by snake or insect or a severe allergic reaction


  • If a bacterial infection is suspected, your veterinarian will choose an appropriate antibiotic and an NSAID (bute or banamine) to keep fever down until antibiotic can take effect.
  • If inflammation is suspected, your veterinarian may choose an NSAID (bute, banamine, etc), but may also use a steroid.
  • If a virus is suspected, unfortunately the only treatment is supportive care. NSAIDs will be used to keep fever down.
  • All horses with fevers should be encouraged to drink plenty of water. Hydration is important and some horses will get impaction colics secondary to fever because they are not drinking enough.
  • All horses with fevers should have their temperatures monitored every 6-12hrs and given an NSAID to control fever as necessary, taking care not to exceed the maximum dose.
  • Horses with added risk of laminitis should also have their feet iced/ legs hosed during a fever event as fever poses an increased risk of this disease.
  • Proper biosecurity measures should be taken to isolate a horse with a fever from the rest of the herd.
  • No nose-to-nose contact
  • No water or food sharing
  • Designate one person to take care of sick horse and do not allow designated person to interact with other horses
  • Make a foot bath of 10% bleach outside affected horse’s stall
  • Wash hands immediately after interacting with sick horse

Remember: the vast majority of fevers respond quickly to bute or banamine, are viral, and usually pass in 24-48 hours.

*As you have probably heard, there have been some cases reported of EEE over the last couple of weeks. You should know that all cases have been in horses considered “unvaccinated”, meaning they had not been boostered appropriately for these deadly diseases. Vaccination does protect your horse from potentially fatal diseases.

  • All horses should receive annual vaccination for rabies
  • All horses should receive vaccination for EEE/WEE and West Nile Virus every 6 months
  • All horses should receive annual vaccination for tetanus, then booster as needed for wounds
  • All at risk horses should receive Flu/Rhino vaccine every 6 months

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