It happened one day at a hot, early summer professional rodeo. Tana Renick, 2011 Ram National Circuit Finals Rodeo barrel racing champion, watched as a horse turned the third barrel and headed back down the alley for home. Nothing out of the ordinary, but what Renick heard immediately after the horse crossed the plane of the timer and stopped grabbed her attention. The horse coughed.
“I remembered thinking, ‘that sounds like a bleeder cough,’ and within just a second, blood was gushing out of both of the horses’ nostrils,” recounts Renick “For me, that was a first. I had heard people tell stories of horses gushing blood, but I had never witnessed it.”
The horse experienced epistaxis, or bleeding out of the nostrils, the least common form of exercise induced pulmonary hemorrhage (EIPH), commonly known as bleeding.
Why does EIPH occur in horses?
The most commonly accepted theory for bleeding, according to Jim Chiapetta, equine veterinarian and co-inventor of FLAIR Equine Nasal Strips, has to do with the pressure differential created in the lungs during exercise. A thin membrane in the lung separates the alveoli from the fragile capillaries, in which the red blood cells exchange carbon dioxide for oxygen that is transmitted back into the body.
A horse’s spleen contains a high volume of blood, he says, and the spleen releases large amounts of red blood cells into the bloodstream when a horse becomes excited. This increases the amount of blood, as well as the pressure within the capillaries.
Another bi-product of excitement or exertion is that its heart rate increases, pushing blood through the capillaries at a faster rate, Chiapetta says. This further increases the high pressure on one side of the membrane. An area of low pressure is created on the other side of the membrane as the horse’s diaphragm moves to pull in air. The pressure differential on the membrane creates force, which causes the membrane to rupture. Blood moves from the tiny capillaries into the alveoli in the lungs, and in extreme cases, blood travels up the airways and is seen flowing from the horse’s nose.
However, both Chiapetta and Todd Holbrook, Oklahoma State University Center for Veterinary Health Sciences associate professor and equine section chief, agree that aside from the mechanical failure of the membrane that occurs in all bleeding, other factors contribute to the cause of bleeding. While some are known, many are yet to be discovered. For example, a respiratory infection that makes the membrane weaker, or a shift of the intestinal organs caused by the horse moving at speeds faster than a walk, have also been sighted as potential causes of EIPH.
Holbrook, who specializes in internal medicine, notes that laryngeal hemoplegia, also known as “roaring,” can cause restriction of the equine airway. This causes the animal to work harder to breath, again creating a negative pressure differential on the membrane and causing the capillaries to rupture.
The Unseen Enemy
While the American Veterinary Medical Association claims that more than 80 percent of horses bleed following strenuous exercise, the condition often does not result in visible blood in the nostrils.
“For all those horses that you see a little blood at their nostril, there are hundreds of them that are bleeding that you don’t ever see because most often the blood doesn’t come out,” says Holbrook.
In Thoroughbreds, only around 5 percent show blood in the nostrils after performance, added Holbrook, who serves as the equine section chief veterinarian and specializes in internal medicine.
“Bleeding goes on in the lungs, so 90 percent of the time you never see it even though they are doing it,” says Chiapetta.
Even if a horse is not bleeding from the nostrils, other signs indicate the horse could be bleeding internally, according to Holbrook. Indicators of bleeding include reduced performance, slow or poor recovery, coughing, excessive swallowing, and, under extreme circumstances, behavior problems such as refusing the alley.
Rick Kutz, owner and chief veterinarian of Raintree Equine Services, cautions that these symptoms are more likely to occur during hot, humid summer months.
“When the weather changes from moderate to hot and humid, all of the sudden we start to see more bleeders,” Kutz says. “That is the time of year you see the ones who have maybe never bled before, start to bleed.”
P.J. Burger, 2009 NFR qualifier, agreed. She added that while rodeoing she sees more horses bleed in the southern states where the climate is hot and conditions are typically dry and dusty.
“My first reaction when I see a horse bleed is, ‘OK, call your vet, get him scoped and find out where it is coming from,’” explains Burger.
Holbrook noted that a horse should be examined by a veterinarian following any incidence of bleeding in order to rule out other possible causes of the blood seen in the nostrils. However, he explained, by definition, if a horse has blood coming from its nostrils after exercise, the horse has experienced EIPH.
Diagnosis and Treatment
Holbrook explained that the only definitive way to diagnose and measure the level of severity of the condition is to have a veterinarian scope the horse within 30 minutes of performance or perform a bronchoalveolar lavage. A bronchoalveolar lavage is a washing of the lung to obtain a fluid sample, which allows the veterinarian to determine if there has been any blood in the lung within a month of suspected bleeding.
While the bronchoalveolar lavage is the most accurate way to determine if a horse has bled, because the procedure requires the horse to be sedated, scoping is the most common method of detection, Chiapetta says.
“Over time, every instance of bleeding adds to the fragility of the membrane between the airways and blood vessels in the lungs, making the horse more vulnerable to bleeding next time,” Chiapetta said.
When a horse bleeds, the horse’s lower airway becomes inflamed, he added. Blood remaining in the horse’s airway can cause respiratory infections because blood is an optimal environment in which bacteria and organisms can grow.
After seeing one of her horses bleed, Burger noted that she likes to have a vet prescribe a round of antibiotics in order to ensure that a lung or respiratory infection does not ensue.
However, Holbrook cautions against using antibiotics every time a horse bleeds. He added that, while the risk of a horse getting an infection is real, so too are the risks of resulting complications, such as diarrhea, when using antibiotics in adult horses.
“Anytime you do something, you have to make sure that above all else, you do no harm,” Holbrook says.
He advised evaluating antibiotic use on a per horse basis by looking at factors such as the distance the horse traveled in a trailer prior to bleeding and the degree to which the horse bled.
After determining the horse is a bleeder and working to rebuild the animal’s immune system, prevention of further bleeding occurrences should be at the forefront of the owner’s mind, says Holbrook.
Chiapetta notes that research has shown that, in contrast to some beliefs, no method or treatment completely prevents bleeding, but several proven methods are used to effectively control it.
“There are so many things on the market, some things work, and some things don’t,” Burger advises. “In my experience, I think Lasix is about the only thing that’s going to prevent it.”
Like Burger, Renick says she has seen many products on the market that claim to prevent bleeding, but in her experience, she has learned of no perfect solution to the problem.
“A lot of times, I’ll run a bleeder on Lasix,” Renick said. “I’ve tried herbs and this and that, but my experience with it is that every horse is different, and it just depends on the situation.”
Both Chiapetta and Holbrook agree that furosemide, also known as Lasix, and FLAIR equine nasal strips are the only treatments clinically proven to prevent bleeding.
Chiapetta also cited research done by Kansas State University demonstrating high doses of Omega-3 fatty acids fed in high doses over a three-month interval will reduce bleeding, but added that, to their knowledge, no products on the market are known to contain high enough levels of Omega-3 to reduce EIPH.
Kutz suggests that products such as Ventipulmin and supplements containing vitamin C and K powder used in addition to Lasix can help a horse with EIPH.
Lasix, Chiapetta explains, is a diuretic that works by causing horses to excrete about 15 to 20 pounds of water from their system via urination. This causes their blood to drop in volume by decreasing the amount of water in the blood stream.
Lasix is one of the top regulated drugs in the racehorse industry, he adds. The drug is administered about four hours prior to competition, and dosages vary depending upon the severity of the horse’s condition, the regulations of the state or the individual competition, and the guidance of the administering veterinarian.
“It’s a fairly safe drug,” Holbrook says. “I don’t really worry all that much, even about the highest dose [10 cc] we administer or recommend administering. It is possible that lower doses [3-4 cc] can be effective in certain individuals, especially dependent on how severe their condition is and how hard that individual runs.”
However, Holbrook says he tends to lean toward a more conservative, lower dosage when recommending the drug to patients because there is a slight risk of dehydration. The risk of dehydration could increase if the horse is competing in a multi-run event, takes place in hot conditions, or is asked to work for long periods of time.
Holbrook suggests that electrolytes or salt should be added to the horse’s diet to help prevent the horse from becoming dehydrated when using Lasix.
Chiapetta said studies have shown, at low rates of speed, Lasix reduces bleeding by about 70 percent, while FLAIR nasal strips reduce bleeding by about 35 percent. However, when tested at high rates of speed, the FLAIR strips work as well as Lasix, both reducing bleeding by about 50 to 55 percent.
According to Kutz, Ventipulmin also helps the horse to breathe easier during a run.
“Ventipulmin dilates the alveoli of the lung, taking away some of the intrinsic pressure in the lung,” Kutz said. “You get improved breathing, less strain and less of a chance of bleeding.”
He added that vitamin C and K supplements added to a horse’s feed could help strengthen the blood vessels, decrease bleeding and increase clotting.