Answers to some head-scratching canine otitis questions

July 12, 2019

Veterinary dermatologist Dr. Darin Dell weighs in on some particularly perplexing aspects of this ear-itating condition.

Ermolaev Alexandr/stock.adobe.comDealing with canine otitis can be complicated for many reasons-client communication being one of them.

“I once had a client call in and say that her dog had ‘helicopter ear,'” says Darin Dell, DVM, DACVD. “It took 10 minutes to figure out that she was trying to say her dog was shaking its head.”

Set your sights on cytology

According to Dr. Dell, you need to perform a cytology every time you see your otitis patients.

“You need to know what you're dealing with,” he says. “You need to know where you started so you know where you are in two weeks if the patient isn't better.”

While Dr. Dell may not be able to act as a translator between you and your clients when it comes to otitis, he's a tip-top resource on every other aspect of the condition. Check out some of the questions he fielded during a recent Fetch dvm360 conference session.

Q. Even though allergy is the primary cause in one of my patients, I've only ever seen otitis in one of its ears. Why don't I see it in both?

A. Each episode of otitis changes the ear canal for the worse, and these changes add up over time. After the first episode of otitis, that right ear never went back to normal, so the next ear infection showed up in that ear first. And the next one. And the next one. It's become predisposed by the chronic inflammation that is under the surface.

Q. How important are cultures?

A. Dermatologists don't culture the external ear canal very often-in part because the sensitivity is based on blood levels of antibiotics, and we can get much higher concentrations when we do topical therapy. Cultures also don't take into account biofilm (that slimy stuff that makes everything goop up to the walls), and they will include antibiotics you can't get in topical formulations.

So, rarely is the answer, “I did a culture, so now I'm going to have a drug compounded to put in the ear.” It seems like the easy choice, but it's probably not the right choice. Topical therapy really is the cornerstone of otitis treatment. Unless you have otitis media or you see a lot of white blood cells in your otic cytology, an oral antibiotic isn't going to do much for the patient. It's not necessarily wrong, but depending on your feelings about overusing antibiotics, you might want to reign that in.

Q. There are so many ear washes available. What's the best kind to keep in my hospital?

A. If you were to keep only one type of ear wash in your clinic, your best bet would be a general ear cleaner with a neutral pH, such as Epi-Otic or EpiKlean. These are safe in any ear and can be used for routine cleanings. That being said, depending on your location and the types of patients you tend to see, you might want to stock other options as well.

If you regularly see dogs with thick, dry wax (such as cocker spaniels), you might want to stock a cerumenolytic too. I divide cerumenolytics into two categories: those I'd only use in the hospital and those I'd send home with a client.

Cerumenolytics containing squalene are in the first category. These are useful when you have an anesthetized dog or cat with an ear that's packed with concrete-like wax. However, because these products are so greasy (the idea is that they mix with the wax and lubricate the ear canal so things can come out), I keep them in-house only. If I want the client to use a cerumenolytic at home, I recommend micellar solutions. These contain micelles that are really good at dissolving thick, dry wax and are less messy.

Acidifying ear washes are as advertised-they acidify the ear canal. They make the canal especially uninhabitable for yeast because yeast likes a more basic environment. I don't particularly like these products because they can irritate sensitive ears, and pretty much every ear I see in my practice is sensitive. But if you live by a lake and have lots of Labrador patients, you might find it useful to keep one of these on hand. Just keep in mind that they can irritate the ears and that they're good for yeast infections but not bacterial infections.

On the topic of bacterial infections, cleaners containing Tris-EDTA are another option and should be used whenever you see rod-shaped bacteria on cytology. Here's why: Most of the time, rod-shaped bacteria are gram negative, and Tris-EDTA takes this gram-negative bacteria and jabs holes in the walls so your antibiotic or antiseptic can find its way in. It's a pre-treatment for the infection.

There are lots of Tris-EDTA options. Typically, they're combined with ketoconazole or miconazole to help prevent Malassezia (but I wouldn't use them to treat a Malassezia infection). Sometimes they're combined with chlorhexidine, which is the kind I tend to use because chlorhexidine is also antibiofilm, and many of the ears I see also have some slimy stuff in them.

With rod-shaped bacteria, it's important that you clean the ear and then medicate it about 15 minutes later. We want to flush out as much as we can, and then we want whatever's left to be weaker so we can throw an antibiotic at it and have it be more effective.

Read on for more Q&As as well as a list of otitis client handouts...

 

Help clients hear you out

Use these handouts to get you and your clients speaking the same language:

>Types of otitis and what to watch for

>What to know about otitis externa

>Fight ear infection fiction

Q. How often should ears be cleaned and for how long?

A. As I just noted, for ears with rod-shaped bacteria, you'll clean the ear right before you medicate, which might be twice a day. On average, for general infections, the ear may only need to be cleaned twice a week. This may need to be adjusted based on the breed, the patient's behavior, the client's behavior and how much debris you see in the ear.

Cleaning should continue for several weeks after the infection has cleared. So for example, in an ideal situation, you might start your patient on an ear wash and medication. Two weeks later you recheck the ear and the infection is gone. At this point, you can stop the medication, but you're going to continue the ear wash for another two to four weeks and then check the ear again.

Q. Can otitis be caused by hair in the ear canal?

A. No, not on its own. Hair is a predisposing factor, but it's not a causative factor. Surprisingly enough, there are poodles with ears full of hair that don't have ear problems. It does happen. But there are also a lot of poodles that have an allergy and hair in their ear canals, and that's a mess. It's one more factor, but it's not a cause.

I can't mention “predisposing factor” without quickly addressing the PSPP system, which stands for primary, secondary, predisposing and perpetuating factors.

Primary factors can induce otitis in a normal ear and include allergy, autoimmune disease, foreign objects, masses, endocrine dysfunction, vasculitis and parasites. All otitis cases fall into one of these categories.

Secondary factors can create disease in an abnormal ear. In other words, the ear already has one of the primary factors, and then it gets a bacterial or yeast infection. Dermatophytes, overcleaning and medication reactions are all secondary as well. As veterinary professionals, it's important that we stop saying otitis is caused by bacteria. It's made worse by bacteria.

Many of our clients like to say, “Oh, he has dirty ears because he's a Labrador and loves to swim all the time.” Or, “He's a cocker spaniel with floppy ears, so of course he has ear infections.” Help them understand that these can be predisposing factors, but they don't cause otitis on their own.

Perpetuating factors are the forgotten ones, but I'd say every otitis case you see is going to have excess cerumen production, inhibited epithelial migration and edema in the canal (though we can occasionally see tympanic rupture and otitis media as well). These three things are going to continue longer than it takes you to kill the bacteria or yeast, and if we don't address them, that infection is going to come right back because we haven't normalized the ear canal itself.

PSPP power

The strength of the PSPP system lies in its ability to make a couple of fundamental points about otitis externa very clear-to both the client and the veterinary professional. First, says Dr. Dell, otitis externa is typically a sign of underlying skin disease, not a diagnosis in and of itself. And second, identifying and resolving or controlling the primary cause of the condition is crucial for long-term success.

But alas, the PSPP system probably won't be able to help you translate what your client means when he calls to say his pet is exhibiting “leg thumping” (as one of Dr. Dell's clients did). Perhaps you can take comfort in the fact that even the expert struggles in this area.