Ask the Vet: Otitis externa — The bane of all veterinarians

Ask the Vet: Otitis externa — The bane of all veterinarians

By Matthew Kearns, DVM

This time of year (actually throughout the summer and fall) we have an uptick in ear infections. To call every dog or cat that comes in with itchy ears an ear infection is misleading. Otitis externa means “inflammation” (not infection) of the external ear canal. The bacteria and yeast we treat with medications fall into the category of “normal flora,” or organisms found in low numbers in healthy ear canals. 

Usually some other trigger is involved and the normal flora overgrow. Parasitic infections (ear mites), pets that swim a lot/get water in their ears, or ear trauma (plucking hair, etc.) are triggers for acute, or nonrecurring problems that are easy to treat. 

Chronic, recurrent infections are almost always secondary to allergies. I actually consulted with a veterinary dermatologist and she estimated that between 80 and 90 percent of all recurrent otitis externa in dogs is related to allergies.    

The anatomy of the ear plays a role in predisposing patients to ear infections. The normal canine and feline external ear canal have and “L” shape, with both a vertical and horizontal component to it leading to a greater distance from the opening of the ear canal to the ear drum. Additionally, clearing the healthy ear canal occurs through a slow process called migration. 

The ear canal contains epithelial cells (those similar to skin), ceruminous cells and apocrine cells (cells that produce earwax). Epithelial cells will turn over, or be replaced every few days and, along with a small amount of earwax, migrate toward the entrance of the canal. Once at the entrance a good shake of the head sends it out to the world. If the lining of the ear canal becomes inflamed, it narrows due to swelling (most likely due to some sort of food or environmental/seasonal allergy) and excessive ear wax is produced. This combination not only overwhelms the ear’s ability to clear the wax, it also leads to a warm, dark and moist environment and allows the normal bacteria and yeast to go crazy.

Certain breeds such as Labrador retrievers, golden retrievers, cocker spaniels, shar-peis and mixed breeds of this type have predisposing factors such as hair in the ears, floppy ears, narrow ear canals or a combination. 

Now, this does not mean that every member of these breeds is guaranteed to have chronic ear infections, rather it means that if you have a member of these breeds and they have even low-grade allergies, the ears can spiral out of control quickly. We are also starting to encounter antibiotic strains of bacteria (such as Staphylococcus) in chronic recurrent otitis in veterinary medicine.  

The main point of all of this is if your pet has chronic, recurrent ear infections, it is important to look for an underlying allergy and treat the allergy. Sometimes it can be a veterinary-approved prescription diet or sometimes the newer, safer allergy medications. Remember to discuss this with your veterinarian.

Dr. Kearns practices veterinary medicine from his Port Jefferson office and is pictured with his son Matthew and his dog Jasmine.

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