Horses loaded up and ready for the long haul!
   We all know that air travel often leads to the common cold in people, but can the same thing happen to our horses in the trailer?

   Yesterday, as I boarded a plane in Indianapolis for a trip to the East Coast (part work, part play), I realized too late that I had not packed my Airborne. As the doors closed and the cabin pressurized I heard the sounds that give every traveler that sinking feeling; coughs, sniffles and sneezes. I knew that no amount of in-flight complimentary orange juice would help, I was going to get a cold. It happens countless times every day all over the world, passengers, tired and stressed from the airline experience, mixing germs in the ultimate petri dish, a crowed plane. 

   All this thought of impending illness reminded me of one of the reasons for my trip east. The data for the final research project that I performed during my residency was analyzed and all that was left was to write the paper. Yes, I know, 18-months is a very long time to wait, and yes, I had probably forgotten more about the project than I knew in the first place, but sometimes science is slow, or sometimes researchers get busy with other things (moving thousands of miles, new jobs, new companies, puppy raising, wedding planning) and that little project gets forgotten. We had waited too long and this trip home was a perfect opportunity for my co-author and I to lock ourselves in an office and just get it written. The project looked at tracheal mucociliary clearance, a very important factor in the development of transport-associated pleuropneumonia in horses, or “shipping fever.”

   You see, humans aren’t the only ones who get sick after travel. Shipping fever is a well-described syndrome in horses, cattle and any other animals that are packed in trailers and sent around the country.  Shipping has been shown to increase stress markers, such as cortisol, in animals, which can lead to a decrease in immune function. In horses we recognize that tracheal clearance plays an important roll. The lining of the trachea is covered in microscopic finger-like projections called cilia (from the Latin word for eyelash). These cilia beat synchronously to move tiny particles of dust, debris and bacteria up the trachea, away from the lungs, where it can be coughed up. When we ship horses, we commonly tie them in some fashion so that their head is in an upwardly fixed position. Research done by Dr. Sharanne Raidal of the University of Sydney has shown that this prolonged upward fixation of the head and neck significantly decreases the rate at which particles move out of the trachea and that this leads to a significant increase in the number of bacteria and inflammatory cells found in the trachea and lungs. Combine this with decreased immunity, bits of hay and dust from the hay net being blown around in front of their face, not to mention the pollution of a diesel truck and its no wonder some horses develop pneumonia after shipping. The study I performed, the one I still had to write up, aimed to prove that pre-treatment with clenbuterol, a drug known to increase tracheal clearance, would prevent shipping fever…sadly it did not work as we hoped. It did increase the rate of clearance but this small increase was not enough to combat the barrage of insults that batter the respiratory system during transport.

Millions of finger-like projections called cilia, beat in time to move debris and bacteria up the trachea and away from the lungs. These cilia can be easily damaged by viruses and the stresses of shipping, leading to pneumonia.
So what can be done to protect our equine travelers? Buckets full of OJ at each rest-stop? Giant sized Flinstone’s Vitamins? The solutions may be a bit simpler than that. First things first, don’t ship sick horses. Horses that are already compromised or are recovering from a recent illness are more likely to become sick after shipping. Upper respiratory tract viruses (like the Flu or Rhio virus) can blunt tracheal cilia. This damage can take weeks to a month to heal, leaving that horse even more susceptible. But once you have your healthy horses on the trailer, try to decrease the amount of particles their respiratory tract has to deal with. Ensure the trailer has good ventilation (especially in the winter when we tend to shut up all the windows, a few horses’ body heat in a small space will keep them warm).  Debris in the air can be controlled by soaking the hay for 5-10 minutes before hanging the hay nets (soaking any longer can leach out some of the sugars and decrease the nutrient values, which may not be a bad thing if your horse is an “easy keeper”), or ship them without hay at all. It may not be good for their attitude but it can save their lungs.  Next, let gravity lend a hand. Another study done by Dr. Raidal showed that the ill effects of the upwardly fixed head position can be negated by allowing the horse to lower its head to the ground several times throughout the trip. So when you stop for gas, remove the breast bar and let your horses have their heads, they may be able to empty out some of those bacteria that have been building up.

    Unfortunately no matter how diligent we are, no matter how much OJ we guzzle at the airport, after a long trip some people and some horses will get sick. The best thing we can do for these cases, is recognize the illness and begin treatment as soon as possible. Taking your horses temperature several times a day and monitoring their attitude and appetite closely for the few days after a long trip can help you pick up on the early signs of illness. If you do have concerns about one of your travelers, contact your veterinarian. He or she can do a thorough assessment of your horse and may recommend blood work to look for signs of systemic inflammation. Many times, pneumonia in horses, if treated early, can be resolved quickly without too much time out of the saddle. However, left untreated, bacterial pneumonia can become very severe, require hospitalization and even be life threatening. In fact, studies out of Japan show that shipping fever is one of the leading causes of morbidity and mortality in racehorses.

    Don’t let your horse fall victim to this potentially terrible disease. Take precautions before, during and after shipping to keep your friends healthy and ready to go on your next adventure!