Portions of this article originally ran in Dr. Samantha Miles’ piece entitled “The 411 on Shipping Fever” in The Horse: Your Guide to Equine Health Care
Whether it is shipping south for the winter, bringing a new horse home, or heading out to a new park for trails, some horses don’t always fare well with long shipments.
Shipping fever is a pulmonary disorder associated with shipment. Studies indicate that the stress response is at fault, resulting in a higher level of ACTH (and therefore cortisol), glucose and white blood cells. The longer the transit time is, the greater the stress response, with pneumonia and pleuropneumonia being potential consequences of a long shipment.
Commonly, symptoms present within 24-72 hours after shipment with only a fever and increased respiratory rate. Often this can be treated with non-steroidal anti-inflammatories (NSAIDs) and be cured. However, at this point, diagnostics are key to differentiate a mild shipping fever from pleuropneumonia. These can escalate quickly and vigilance is important.
To diagnose shipping fever, bloodwork should be run first. Having a baseline white blood cell count is necessary to evaluate the progression of disease. Packed cell volume and total protein will give you an idea of hydration status and will dictate your use of intravenous fluids in these cases. Also useful is a chemistry, or minimally kidney enzymes, as often these horses will be dehydrated and it is important to know their kidney status prior to administering NSAIDs.
An ultrasound will identify pleural roughening (“comet tails”) in mild cases, ranging to lung consolidation, abscesses and pleural effusion in more severe cases. Accurately documenting the extent of pleural involvement and size of consolidation and abscesses will be important when you are later evaluating response to treatment.
Finally, a transtracheal wash (TTW) is a good diagnostic tool to receive a sterile sample for bacteriology. This will help you hone in on the specific bacteria and gauge its sensitivity to your medications.
In severe cases where pleural effusion is significant, a sample of this fluid should also be attained for culture and sensitivity. In these cases, a chest tube may be necessary in order to keep the horse comfortable.
Initially, there are a few things that must be a part of your treatment plan:
- To control fevers, a regular NSAID dose should be given. This should be split throughout the day (e.g. every 6-12 hours depending on severity) in order to consistently maintain a normal temperature.
- Broad spectrum antibiotics must be administered empirically until culture and sensitivity results return.
- Most bacteria in pleuropneumonia will be a mixture of aerobic and anaerobic bacteria, which makes the use of Metronidazole key in treatment. Ideally, oral administration should be used, however in the case of anorexia due to oral administration, giving a per rectum dose is also appropriate. Note that this dose is much higher than the oral dose due to less effective absorption per rectum.
- Intravenous fluid therapy is important in those horses not drinking or already dehydrated. Re-checking packed cell volume (PCV) daily will help to determine how long fluids should be continued.
Other options depending on severity of case:
- This will open up the airways and allow clearance as well as better penetration of antibiotics.
- In our experience, nebulization with antibiotics is often well tolerated and provides a good adjunctive response.
- Chest Tube
- For managing severe pleural effusion, a chest tube may be necessary to keep the horse comfortable.
- Rib Resection
- In cases that are refractory to treatment due to a high amount of fibrinous material within the pleural effusion, a rib resection is possible to clear the material out. This is not a procedure recommended unless the horse is not responding to initial treatment for prolonged periods.
As with everything in veterinary medicine, prevention is key. In order to avoid shipping fever, use a low-dust hay and ensure plenty is given to the horse for the journey as well as adequate ventilation. Allowing the horse to lower its head during shipment periodically has been shown to decrease risk. Some may choose to administer IV fluids prior to trailering to prevent dehydration stress on the body, especially horses who do not usually drink when trailered.