The 411 on Shipping Fever

Ready for the Road Trip! (Photo: Kate McIntyre)

The height of travel season is upon us and horses will soon be traveling throughout the U.S. and beyond for winter competition. Some horses don’t fare well during a long trip, be it heading south for the winter or across the state to traverse new trails.

Horses can often develop a pulmonary disorder associated with transport called shipping fever. Researchers have shown that these horses’ stress response is at fault, causing adrenocorticotropic hormone (ACTH), glucose, and white blood cell levels to rise. Higher ACTH levels lead to increased secretion of cortisol, known as the stress hormone. The longer the horse’s transit time, the greater the stress response, potentially resulting in pneumonia and pleuropneumonia.

Clinical signs of fever and increased respiratory rate usually appear within 24 to 72 hours after shipment. Veterinarians can often resolve this by administering non-steroidal anti-inflammatories (NSAIDs). However, at this point, diagnostic tools are key for differentiating between a mild shipping fever and pleuropneumonia, the latter of which can escalate quickly.

Once diagnosed, your horse’s initial treatment plan will include the following therapies:
- NSAIDs - A regular NSAID dose will help control fever. This should be split throughout the day (e.g., every six to 12 hours, depending on severity) to maintain a consistently normal temperature.
- Antibiotics - Your veterinarian should administer broad-spectrum antibiotics empirically (based on what has worked for them in the past for similar cases) until they receive culture and sensitivity results from the lab. Most bacteria in pleuropneumonia are a mixture of aerobic and anaerobic (requiring oxygen to survive vs. not requiring it) bacteria, which makes the use of abroad-spectrum antibioticand metronidazole key in treatment. Ideally, metronidazole should be administered orally; however, a per rectum dose is appropriate if the horse is off his feed. Note that this dose is much higher than the oral dose due to less effective absorption.
- Intravenous (IV) fluid therapy - Horses that aren’t drinking or are already dehydrated need IV fluids. Rechecking PCV daily will help determine how long to continue fluids.

As with everything veterinarians treat, prevention is key. To avoid shipping fever, offer your horse plenty of water and low-dust hay during the journey and ensure he has adequate ventilation. Allowing the horse to lower his head periodically during shipment has been shown to decrease shipping fever risk. Some owners might choose to have their veterinarians administer IV fluids prior to trailering to prevent dehydration stress, especially in horses that do not usually drink when trailered.

Want to find out more? See the The American Association of Equine Practitioners (AAEP) Forum article in the October 2017 issue of The Horse magazine authored by PBEC's own Dr. Samantha Miles!