The Horse

DEC 2018

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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16 December 2018 The Horse | to that discharge, you definitely want to have it looked at," says Lascola. "If it's a severe pneumonia (which is most commonly caused by bacteria and less commonly by viruses or fungi), when you watch them breathe they might have an increased respiratory rate." Another sign that a horse could have an infection, whether mild or severe: He might be hanging out toward the back of his stall and doesn't want to inter- act with people, says Mazan. The most common viral causes of snotty noses are influenza, rhinitis A and B, and rhinopneumonitis caused by equine herpesviruses-1 and -4. Equine viral arteritis virus (EVA) is a less com- mon cause. "There's also equine herpesvirus-2, which is ubiquitous," says Mazan. "We used to think it was unimportant, but now we know it's a fairly important cause of snotty nose, especially in younger horses. There's no vaccine for that or for EHV-5, which again can cause a relatively low- grade viral disease in younger horses." Lascola warns that horses with viruses can be at risk for complications. "It does take time for the airways to heal after a vi- ral infection, and so they are at increased risk during that time for a secondary bacterial infection, especially if they are being transported or being worked." Bacteria Among the most common bacterial causes of nasal discharge are Streptococcus equi subsp. zooepidemicus, which can lead to pneumonia, and S. equi subsp. equi, which produces strangles. Often horses with strangles don't develop nasal discharge until later in the disease process, once internal abscesses rupture. Then, a purulent discharge can drain from the guttural pouches (more on these coming up) into the nasal passages and out bilaterally through the nose, says Lascola. Yet another cause of this type of discharge, sinusitis (inflammation of the sinus tissue) can be due to a bacterial in- fection or dental disease, such as a tooth root infection. Scenario 3: The horse has a flowing bloody nasal discharge. Any horse with bright-red blood in his nasal discharge should be seen by a veter- inarian immediately, says Mazan. Unless the horse just finished strenuous exercise resulting in exercise-induced pulmonary hemorrhage (EIPH, or "bleeding"), a fungal or bacterial infection within the guttural pouches could be to blame. The guttural pouches are sacs of air located just beneath each ear that help the horse cool the various cranial nerves and the internal carotid artery, which car- ries blood to the brain, and the maxillary carotid artery, which supplies blood to the rest of the head. Mazan says fungal infections can re- side on this internal carotid artery. "When you scope the guttural pouches, you can watch those carotid arteries beating," says Mazan. "You're only four cell layers away from disaster. If the fungal infection erodes that artery, you can bleed out in a big hurry. It could be minutes." In such a situation, a trickle of a nose bleed becomes a gusher. And if an owner misses early signs of bloody discharge, the results are devastating; a horse gush- ing blood can bleed out in minutes. Fungal infection discharges can be clear to yellowish to honey-colored, are usually (but not always) unilateral, and can smell bad. Additional signs of a fungal infection can include cranial nerve abnormalities, such as the horse holding or swinging his head oddly to one side due to loss of innervation, swallowing issues, and signs of Horner's syndrome (e.g., drooping eyelids, sunken eyes, a raised or swollen third eyelid, constricted pupils, abnormal sweating on the affected side). Other causes of unilateral bloody nasal discharge include sinus cysts or foreign bodies (such as a stick) lodged in a nostril. Scenario 4: The horse has unilateral bloody discharge, but it is dark rust in color and mixed with lots of mucus. A horse with rust-colored bloody discharge—indicating it's not from a fresh FRANK SORGE/WWW.ARND.COM Stalled horses are susceptible to environmental irritants, such as dust, which can cause them to develop bilateral watery or mucoid discharge. THE NOSE KNOWS A horse with thick yellow discharge coming from both nostrils is most likely battling a bacterial or viral infection. AMY K. DRAGOO

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