What is Otitis Externa?
Otitis externa is the inflammation of the outer ear and the upper ear canal and can be caused by allergies, mites, or other infections and diseases. It is not common in horses, and when it does occur it can cause swelling, pain, intense itching, and behavior changes in your horse. Cases of otitis externa should be evaluated by a veterinary professional as some some infections can spread deeper into the ear canal and lead to partial deafness, rupture of the eardrums, and even neurological problems if left untreated.
Otitis externa, or the swelling and inflammation of the outer ear, is an uncomfortable and unsightly disorder that should be evaluated by a veterinarian.
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Symptoms of Otitis Externa in Horses
Infections in the ears generally have symptoms that are remarkably similar whether they are caused by bacteria, yeast, or mites.
- Blood blister on the ear flap
- Changes in behavior
- Discharge from the ears
- Ear pain
- Foul odor from the ears
- Head shaking
- Head tilting
- Redness or swelling of the ear flap
- Scratching or rubbing of ears and head
- Sudden head shyness
Swelling of the ear canal can be divided into three categories, based on the depth of the infection within the ear canal.
- Otitis externa- Infections of the outer ear, often initiated by ticks or other foreign objects in the ear
- Otitis media- This infection is located within the middle ear and may cause inflammation in the labyrinth of the ear as well. Either otitis externa or interna can extend into the middle ear
- Otitis interna- Infections in the deepest part of the ear can also inflame the labyrinth in the ear and if untreated has been known to lead to meningitis
Causes of Otitis Externa in Horses
Otitis externa is often initiated by the bite of a tick or by a foreign object that is lodged in the upper part of the ear, which then develops a bacterial or yeast infection. In some cases, infestations of mites, allergies, auto-immune disorders, and some illnesses may also cause swelling of the ear, with or without an additional infection.
Diagnosis of Otitis Externa in Horses
Your veterinarian will usually perform a full physical during your visit to check the patient’s overall condition and standard blood tests, such as a biochemical profile and complete blood count, can help uncover any systemic infections as well as imbalances in the blood. Otitis externa is similar in appearance to many other disorders including infections by molluscum contagiosum, mites, and some types of tumor. The examining veterinarian will want to take a sample of the affected skin to perform a microscopic evaluation of the tissues, also known as cutaneous cytology. Conventional microscopes will be able to use this to rule out conditions like mites and other parasites, however, an electron microscope will be needed to identify any viral particles and some bacteria.
In some cases, multiple disorders will be implicated in the swelling of the ear. Biopsied tissue from the ear will also be evaluated to rule out cancers and other types of tumors, and an antibody test may be run to rule out specific viruses that may target the ears. In some cases, x-ray imaging of the head and neck will be employed if the veterinarian suspects that the sinuses or dental sockets might be negatively impacted.
Treatment of Otitis Externa in Horses
Treatment of otitis externa is largely dependent on the underlying cause of the disorder. In most cases of otitis externa, NSAIDs or corticosteroid injections are recommended to reduce the swelling and pain in the ear, although the use of both at the same time is not usually advised due to the increased risk of gastrointestinal ulcers. Any ticks or foreign objects that are currently lodged in the ear will need to be removed, and the ear may be shaved if there are any lesions or crusty areas on the ear that require treatment.
Sedation is often recommended for these procedures to make the horse more agreeable during treatments, particularly if the swelling is severe, lesions have developed, or if the horse is head shy. Infections should be addressed using either antibacterial or antifungal medications, and your veterinarian will usually recommend either a topical or oral medication to improve your horse’s ear health. Intramuscular injections of these medications are also available, particularly for infections that have spread and become systemic.
Recovery of Otitis Externa in Horses
Otitis externa can cause swelling and lesions that may be targeted by insects, particularly in the spring and summer months, and controlling the insects in their area is crucial to preventing escalation. Some of the steps you can take to reduce the number of insects in your barns and pastures include:
- Avoid evening and night time turn out in the field, particularly near fields nearby lakes or ponds
- Remove standing water, be sure to empty buckets and clean water troughs regularly and ensure that damp vegetation is also withdrawn from the stable area
- Use a fly cover for the ears, particularly in the spring and summer
- Install a bird or bat house near the property or in proximity to lakes or ponds on the property. Birds and bats are voracious predators of flying insects
- Reduce the lights at night
- Spray the barn area with a suitable insecticide