Effective otitis externa treatment starts with cytology—identifying the exact cause ensures better outcomes and fewer repeat cases. If you work in private practice, you cannot go far into your day before a case of otitis externa falls into your lap. They will come in many different types, smells, and drainages, but just like the guarantee of a sunrise, those ear issues will show up. Some will leave you with very little wonder, like the cocker spaniel with those long droopy ears and the yellow creamy rod bacteria whose smell seems to permeate the wallpaper. How about the Labrador retriever, still wet from its last swim, and that undeniable smell of a locker room hitting you in the face as you walk into the room? Yes, your old friend Malassezia yeast is here for a visit. With experience, it will not take long to formulate treatment plans on these examples, but 20-plus years of practice have taught me not to assume anything. Do you have a protocol for otitis externa cases you or your hospital follow? How do you come up with a medical plan? Some will walk out of the exam room after a “see and smell,” pick up a usual multi-faceted medication, and see what happens. There are a lot of scenarios where those “shotgun meds” will improve, and guess what? Some issues will improve despite your plans. I believe there is a better way. I will walk you through several very common scenarios to improve your ability to treat more precisely and prevent some of those repeat offenders from the next return trip. See and smell Before we get too far, let us talk about the physical examination. There is no escaping the fact this step sets us up for success or failure. An otitis externa case can come in many forms, some easy and some not-so-easy. Some will require a muzzle, and others might even need prayer. Are there redness and irritation? Drainage or discharge? If so, what color is it? Lichenification? Is this a bilateral or unilateral issue? These are all observations that are very helpful in determining the underlying issue. Are there conformation issues, such as chronic changes from past problems or floppy ears that do not allow airflow or drying? Can you even touch the ear or ears involved? There are many cases where you can pick the world’s best protocol for the issue at hand, but if the owner cannot touch the ear due to pain, you will fail if you put them in charge of at-home treatments. All the above must be evaluated and considered to pick the correct treatment and identify how it will be performed and at what length. A little more than a decade ago, my hospital began performing cytology on all our otitis externa cases to determine the exact bacteria and/or yeasts causative to the issues at hand. Yes, there are instances where we find exactly what we think we will find, but more times than not, we see multiple issues that need to be addressed. I believe these constitute most of our “repeat offender cases” from other clinics, and if you are not evaluating all the causes, they will continue that trend. These “ear preps,” as we call them, are easy to make, requiring only a few cotton-tipped applicators, a glass slide, and some Diff Quick stain. More often than not, after evaluating the slide, I bring the client back to show them the findings and make the diagnosis “real” for them. I highly recommend this, especially for those problematic cases. "An otitis externa case can come in many forms, some easy and some not-so-easy. There are some that will require a muzzle and a few that might even need a prayer." Scenario 1: The chronic “yeasty” Labrador ear I am not sure I need to say more in describing this one, but it is a common otitis case. It might be a golden retriever or of the many “doodle” varieties, but this case will present very commonly. Standard procedures are performed first, followed by cytology to determine who is at this party. Is it only Malassezia yeast, or are there others? Chronic lichenification? Experience tells me you will also have cocci bacteria, leading to more inflammation, and if you are performing an ear cytology, you will be able to prove it. These cases are interesting because they feel too easy and can get you in trouble. Several types of topical medication will make these symptoms and present conditions, go away, but for how long? It would help to consider everything, such as the owner’s ability to administer treatment. These cases respond best when you pair an ear cleaner targeting the yeast species with a topical to decrease inflammation and target the specific bacterial infection. Over the last several years, my protocol for this presentation has involved two products. First, I use a medicated flush or cleaner before applying medicated drops for the bacteria. For my chronic Malassezia cases, after initial treatments are completed, I have my clients begin using an ear cleaner weekly then expand to bimonthly or beyond to decrease the reoccurrence of the Malassezia species. There is a certain amount of the population where the yeast grows very well on the skin (some even become allergic to Malassezia), and this protocol has worked well to decrease recurrence. On the bacterial side of this otitis externa type, I use a gentamicin/mometasone/clotrimazole combination. Several brands provide this, and I have used them all. I do not recommend a specific brand, as all have worked very well within my hospital. For the pet that will not cooperate or the owner who might not be the most diligent, I have found cleaning the ear very well in the hospital, and applying an otic solution (florfenicol/terbinafine/mometasone) has worked very well for me. The one recommendation I have is to follow up with those patients two to four weeks later to develop a plan for long-term care and likely an at-home cleaning protocol to limit the return of the Malassezia to the ear. Scenario 2: The “creamy” cocker ear These are another somewhat common otitis externa case. Beginning the physical exam, you will first encounter a strong smell—not the “locker-room” smell of a Malassezia case, but a very pungent smell you cannot seem to shake. Upon lifting the ear or ears (these tend to be more unilateral in my experience), you will find a generally yellowish creamy discharge that is unmistakable. These ears are very irritated and can also be very painful. Careful evaluation of the eardrum should be completed because these cases can go from an external case into a media case very quickly should the tympanic membrane become breached. Cytology, in these cases, generally produces large quantities of rod bacteria, almost always Pseudomonas, and many inflammatory cells. Treatment for these cases tends to differ significantly from the yeast/cocci case described before. The rod bacteria/Pseudomonas otitis externa tends to be a combination of topical and systemic medication. I like to use a ceruminous cleaner, first in-house, teaching the owner how to clean the ear properly and ensuring a good start for the patient. This cleaning should be done daily and possibly more often, if necessary, throughout the treatment. Medically speaking, I use an oral prednisone dose (0.5-1 mg/kg PO q 24 hrs. for a week or more). This duration is based on the amount of inflammation present and will vary from case to case. Other glucocorticoids, such as triamcinolone, prednisolone, or dexamethasone, can be used, but I tend to stay with traditional prednisone. Oral antibiotics are the next step to be determined. There can be cases of resistant bacteria, especially if you are tackling a case that has either been battled previously or is a second opinion. If you are dealing with a recurrent case or your new patient’s owner talks about how their “old vet” could not fix it, you should probably culture the ear and treat it accordingly. For new cases, I begin with enrofloxacin (10-20 mg/kg PO q 24 hrs. for 10-14 days). Marbofloxacin (2.5-5 mg/kg PO q 24 hrs.) could be another good starting place. Topically, after cleaning, I use an antibacterial/antifungal agent (enrofloxacin/silver sulfadiazine) for the length of the treatment. This will likely take a few weeks, and I recommend rechecking cytology to confirm no more rod bacteria are present at the end of treatment. Scenario 3: The “no touchy” terrier ear These cases are becoming increasingly common. The patient presents as the little purse princess pup that seems to rule the roost of their household. The patient gets away with everything and has zero manners. The patient gets an otitis case and presents with significantly more pain than expected, and the owners are scared to touch them or treat them at home. So, what do you do? As before, you need to go through the steps and make sure you know why we are in this predicament. What type of bacteria or yeast is present, and what are our options? There tend to be fewer confirmation issues with these, at least initially. If these become chronic, then stenosis can complicate the treatment or at least lengthen the treatment schedule. Based on experience, I would like to discuss all options with the client and confirm their abilities and willingness to treat these at home. Many pets have gotten their bluff in on the owner, and there is fear they will hurt the pet with treatments. Most of these cases are Staphylococcus and respond to many different treatment plans, but I want to set everyone involved up for success. These cases tend to get cleaned by us, in-house, with a ceruminous cleaner, and then dosed appropriately with an otic solution (florfenicol/terbinafine/mometasone) due to the fact the owners show an unwillingness to follow a detailed treatment schedule or show an inability to treat the pet properly when teaching within the exam room. I explain to clients the ears should not be cleaned at home or by a groomer and schedule a recheck for 14-21 days following the placement of the otic solution. These tend to respond very well, and once they recover, I do my best to get the owner involved in some ear-cleaning intervals to train them and their pet for future occurrences. Conclusion Otitis externa cases come in many different varieties, to say the least. Treatments should be determined based on what is presented and why we got into this predicament. Thorough physical examinations, both external and internal to the ear canal, solid patient history, and microscopic evaluations will greatly determine how successful your treatments will be. Just as important is ensuring your client can fulfill your prescribed treatments. As in the last scenario, if your client can not perform the treatments with you present, they will not be able to do them at home. Whatever the case, ensure you set yourself, your client, and the patient up for success. Cade M. Wilson, DVM, is a practicing veterinarian and a three-doctor mixed-animal practice owner in Ardmore, OK. Dr. Wilson has been practicing small animal medicine for the last 20 years and been a practice owner for the last 17 years.
