Breathing Easy

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When the weather turns ugly, we often close up the barn to keep out the elements. It makes us humans more comfortable. However, it’s not necessarily the best thing for our horses. A closed up barn quickly promotes stale, foul air. Elements such as dust and mold in the hay, grain and bedding, dust and cobwebs in the barn, and ammonia fumes from urine all contribute to poor air quality and set your horses up for lower respiratory problems.

Normally the respiratory system’s natural defenses work well at protecting the horse from disease, but in a very polluted environment, the defenses become overwhelmed. Therefore, the emphasis is on prevention rather than treatment.

MOVE THE AIR

Proper ventilation and good air quality are vital to reduce respiratory distress. “If you exhaust the polluted air, clean air will find a way to get in,” says Tom Croce of Thomas L. Croce Architects, Inc. He recommends the barn have:

• openings on all four sides so that at least two can always be open;

• high ceilings over the stalls and a tall center aisle, which help the natural convection currents and provide a large volume of air to reduce the concentration of pollutants;

• dormers on the roof, to bring fresh air into each stall, and cupolas on the roof to exhaust the stale air.

This ideal ventilation system distributes fresh air uniformly through the building without drafts and helps minimize exposure to environmental irritants. “Ventilation is a remedy for poor air quality,” says Croce.

KEEP IT CLEAN

Therefore, it’s important to keep the air as clean as possible. “You’ve got to reduce the dust,” says Dr. Ed Robinson, Matilda R. Wilson Professor at Michigan State University. “Whenever you’re in a dusty environment, it makes everything worse.” Feed high-quality hay, or try lower-dust options such as hay cubes, pellets or hay soaked in water. However, Robinson stresses that hay should be soaked for several hours in a 55 gallon drum filled with water. Alfalfa cubes may also need a bit of watering. Feed hay on the ground or in ground feeders, because head down feeding enables the horse to clear dirt and dust from his nostrils and airway.

Bedding choices matter, too. Poor-quality straw and sawdust cause a great deal of mold spores, dust and small particles. Kiln dried wood shavings are a common, less dusty choice.

Stalls should be thoroughly cleaned at least once a day, preferably while the horses are outside. According to Croce, an ammonia concentration of only .07 percent can scar your lungs. “If you can smell it in your barn, it’s at a point where you need to do something dramatic,” he says.

Other common chores can contribute to air quality problems. Removing cobwebs showers dust down on the horses. It is best to do this task, too, when the horses are outside, or to hose down the barn if possible. Ideally, hay and bedding should be kept in a separate building. If hay must be stored above the horses, it is better if the loft is sealed and hay dropped only when horses are out of the barn.

In addition, the manure pile should be kept away from the barn.

Another preventive measure:?It may seem simple, but “a little water goes a long way in stable management,” says Robinson. Keeping your arena watered regularly and damping your aisles before you sweep will make a big difference.

Finally, to help prevent infections, it is important to maintain a regular vaccination schedule for various respiratory diseases (see accompanying sidebar).

DEALING WITH ILLNESSES

Still, even with proper management, each horse’s tolerance is different, and respiratory problems can develop at any time of the year. Horses congregated at events and those living at large stables are at the greatest risk.

When a horse develops a respiratory problem, it is important to first check for a fever. In the case of nasal discharge, an opaque or white discharge indicates an allergy or inflammation, but mucus that is ­yellow or green signals a bacterial infection.

INFLUENZA

The virus that causes the equine flu is from the same family as the human version, but people are not susceptible to it. It is, however, extremely contagious among horses.

The virus destroys the ciliated cells lining the airways, which sets up the possibility for a secondary bacterial infection. The incubation period is one to three days, and symptoms are present for one to five days, depending on the vaccination status of the horse. Signs of influenza include fever, going off feed, listlessness, nasal discharge and cough.

The infection runs its course in two to ten days, but the horse can still spread the disease for up to six days after the last sign of illness. Therefore, it is very important to keep sick horses isolated.

Treatment consists mostly of supportive care, with antibiotics necessary for a secondary bacterial infection in the lungs. Depending on the severity of the infection, it may take up to two months for the horse’s lungs to completely recover, so it’s important to follow your veterinarian’s advice on when to return the horse to work.

While most people vaccinate their horses for influenza, no vaccine is 100 percent effective, and researchers continue to work on improving influenza vaccines. Every year a panel of equine flu experts, headed by Dr. Jennifer Mumford of the Animal Health Trust in Newmarket, England, meets to discuss the current equine flu situation and the latest research and information on outbreaks worldwide.

According to panel member Thomas Chambers, PhD, of the University of Kentucky’s Gluck Equine Research Center, “Equine influenza viruses in circulation gradually change over time. This is called antigenic drift, and the result is that eventually the equine flu vaccines need to be updated. The last call for updating was in 1995, and since then the new generation of flu vaccines seems to be working. But 2003 saw severe outbreaks of equine influenza in Newmarket and also South Africa. Researchers are working to collect more data to see if another update is needed.”

Vital to determining how well vaccines are working is to get prompt and accurate diagnosis of respiratory infections based on nasal swabs taken when the horse has a fresh fever. A culture of the nasal swab sample can differentiate among the different causes of upper respiratory disease. “If flu is in the swab, it can be examined to see how similar or different it is from the flu strains in the vaccines,” says Chambers. “We urge horse owners and veterinarians to contact their state animal disease diagnostic center whenever they are confronted with respiratory disease, and arrange to collect nasal swabs whenever possible.”

EQUINE HERPESVIRUS (RHINO)

Equine Herpesvirus is also called equine rhino, rhino and rhinopneumonitis. There are four strains of the equine herpesvirus, with strains 1 and 4 causing upper respiratory and lung inflammation. This disease occurs most commonly in foals, weanlings and yearlings. It is possible for a foal to basically be born with pneumonia and die within 72 hours. Therefore, it is extremely important that a veterinarian see any respiratory distress in foals immediately.

The disease is spread via the air and has a one- to three-day incubation period. Signs are similar to those seen in influenza, including fever, depression, going off feed, clear nasal discharge and a dry cough. Treatment is also basically supportive. Vaccination doesn’t prevent the disease, but it does lessen the severity. Pregnant mares should be vaccinated to prevent abortion in the last trimester.

EQUINE VIRAL ARTERITIS (EVA)

EVA indicates an inflammation of the blood vessels. It is transmitted either through the air or sexually, and it produces respiratory symptoms as well as abortion. Its incubation period is three to 14 days, and its symptoms are similar to other respiratory

infections with the exception of bright red nasal and eye tissue and excessive tearing. Isolation for three to four weeks after the last sign of symptoms helps to prevent its spread, and plenty of rest is very important. Usually, horses recover without any incident.

LOWER AIRWAY INFLAMMATION

For years, what most people called “heaves” was referred to as chronic obstructive pulmonary disease (COPD). This condition is also found in people, but the two are not comparable, so to avoid confusion, lower airway inflammation was labeled one of two ways: Recurrent airway obstruction (RAO), or heaves for the severe cases, and inflammatory airway disease (IAD) for the low-grade form.

RAO is characterized by a small airway obstruction that leads to a chronic cough, shortness of breath and exercise intolerance. Early on in the condition, this airway obstruction is reversible until scarring causes permanent damage. The blockage can be caused by mucus and/or debris in the lower airway or by bronchospasm and wheezing, all of which are a result of bronchiolitis, which is an inflammation and spasm of the small breathing tubes.

As the condition progresses, the cough becomes more frequent, and the horse’s exercise tolerance decreases. In late stages, the cough becomes persistent, especially after exercise or feeding. Simply walking may cause shortness of breath because the damaged lungs have become less efficient. The horse has difficulty exhaling completely, so he makes an extra effort, which is a heaving motion with his abdomen. At this point, you will often see the “heave line,” which is a ridge of muscle that runs down the middle of the flank, over the ribs and toward the back of the elbow.

The exact cause of RAO is debatable. “There is a heritability factor for heaves,” says Robinson. However, the question still remains if heaves is simply a result of being in too dirty an environment for too long, or a result of a specific allergic response. “Even when in clinical remission, they still have ongoing inflammation that never quite goes away,” he adds. A little dust, even bringing a horse into the barn to groom him, can cause everything to flare up again for days.

IAD is a more mild inflammatory condition. Horses have some excess mucus, which may or may not impact performance. The horse may breathe normally at rest, but will become short of breath with exercise. The horse may have a slight nasal discharge and a dry, unproductive cough that occurs intermittently when the horse is exposed to cold or dust. Research is ongoing in racing stables as well as boarding facilities to try and determine how common airway inflammation is in the U.S.

Early detection of heaves provides your best chance to control it. Diagnosis is usually based on history and clinical signs, but an endoscopic examination may also be useful. Another diagnostic method is a broncho-alveolar lavage. An endoscope is snaked into the bronchi and secretions are withdrawn. The presence of inflammatory cells known as neutrophils is typical of heaves.

There is no cure for RAO, but the management practices described earlier can greatly improve the horse’s comfort and usability. Broncho­dilators may help during an acute attack to dilate the bronchial passages so that airflow increases; corticosteroids reduce inflammation, thereby decreasing mucus production.

However, medicines will only provide temporary relief. Long-term relief requires removal of the horse from the organic dust source that is provoking the inflammation. For example, giving the affected horse much more time outdoors, away from a closed-in environment, has shown to dramatically diminish symptoms.

As with most things, prevention is key. Keeping up to date on vaccines, quickly removing affected horses and ensuring that your stable management practices encourage a relatively dust-free environment go a long way to breathing easier.