Allergies Often Behind Chronic Ear Infections

By Don Jergler

Many specialists and vendors advise general practitioner veterinarians how to go about treating chronic ear infections, and they say more attention needs to be paid to underlying causes—chiefly allergies.

"Otitis externa is a real common problem with dogs, and it’s a common problem worldwide,” said Brad Phillips, dermatology marketing manager at Virbac Corp. U.S. in Fort Worth, Texas.

Phillips and Heidi Lobrise, DVM, senior technical manager with Virbac, say the top underlying problem is allergic reactions.

Top, an infection in Cushing’s patient. Above, bacteria and Malassezia dermatitis.

If those allergies are not being treated adequately, pets will continue to have ear problems, Dr. Lobprise said.

In the case of allergies, the typical range of therapy is generally recommended, such as altering diets, prescribing medications, skin testing and immune therapy, Lobrise said.

Rusty Muse, DVM, Dipl. ACVD, with Animal Dermatology Clinic in Tustin, Calif., also said many of the ear infections he sees are allergy-driven.

"The majority of animals we see with allergies will have chronic recurrent ear infections,” Dr. Muse said.

One reason Animal Dermatology Clinic sees so many allergy-caused ear infections may be geography. The clinic has eight practices, and five are in Southern California.

"Certainly, allergies are quite common in Southern California,” Muse said.

The region has a year-round growing season and typically has high pollen levels.

"It’s a bad environment for dogs who are genetically predisposed to allergies,” he said, adding that breeds predisposed to allergies include terriers, golden retrievers and German shepherds.

His recommended treatments for allergies include hyposensitization injections and food trials to look for adverse food reactions.

"Another step is performing cytology of the ears, and making sure you’re comfortable what types of organisms are in the ears,” Muse said. "It’s important for veterinarians to be comfortable performing cytology because that will give you a lot of additional information to choose the correct topical therapy.”

Some practitioners go for a definitive diagnosis, while others treat with a broad-spectrum medication and watch for the response. The best method?

"Symptomatic therapy is fine in first- or second-time ear infections,” Muse said. "However, once ear infections are relapsing or recurring or not responding, it’s time to begin a more exhaustive search of underlying primary diseases.”

It’s not always easy to find the underlying cause.

In one study of 100 otitis externa cases published in Vet Dermatology, "Aetiology of canine otitis externa: a retrospective study of 100 cases,” 32 percent did not have a primary cause identified.

Citing those odds, Nancy Zimmerman, DVM, has some advice for the general practitioner.

"Don’t beat yourself up,” Dr. Zimmerman said.

Zimmerman, director of U.S. Marketing at Dechra Veterinary Products in Overland Park, Kan., said she’s seeing a lot of vets turning toward cleansing products.

Driving those sales and interest, in Zimmerman’s opinion, are the number of options available, which have enabled more vets to view cleansing products as a way to help treat chronic ear infections.

When she graduated from veterinary school 18 years ago, there were maybe two or three ear cleaners, she said, adding, "They were pretty much all the same.”

Inflammation

Because a major component of otitis externa is inflammation, in many instances, this inflammation may need to be treated with corticosteroids, Virbac’s Lobprise said.

"In some cases there may be so much inflammation and swelling of the lateral ear canal that effective evaluation and topical treatment cannot be accomplished until the inflammation subsides, often in response to systemic—oral or injectable—corticosteroids. A good topical corticosteroid, such as hydrocortisone aceponate, that has minimal systemic side effects is then ideal for localized treatment of the otitis.”

She also holds that at the time of diagnosis it’s critical to get a good cleansing of the ear canal to remove discharge and debris.

"Not only does this allow better visualization of the canal and tympanic membrane, it also lets the medication come into direct contact with the epithelial surfaces,” Lobprise said. "Routine cleansing of ears in conjunction with maintenance care can also be beneficial, as long as the products are appropriate for that patient, and that no further harm or irritation is done by the cleansing itself.”

Dosage

"Ears can be challenging to treat, particularly with dogs that have been through it before, and ears may be sensitive,” Lobrise said.

Not only are the pets often uncooperative, but pet owners may unwittingly be uncooperative as well, she said.

"Pet owners are not the best in complying with their veterinarian’s instructions,” she said. "Most of the products available today are effective, but that’s when there’s total compliance.”

And compliance is harder to come by when administering medication can be difficult, Lobrise said.

"You take pets that are hypersensitive, and they do not want you messing with them at all,” she said. "You get into the second or third day and it’s difficult for pet owners. They find that more of the medication goes on them or the couch than it does the dog’s ear.”

Virbac’s EasOtic comes in an airless pump canister. It is designed to be used at any angle, even upside down, and one press will deliver the exact amount of medication in the ear. The product requires one dose per day for five days.

Scoping

A big help in better management and assessment of the ear canals, said Animal Dermatology Clinic’s Muse, is video otoscopy.

"Learning adept manipulation and utilization of the video otoscope gives much more information in the initial assessment of the ear canals, status of the tympanic membrane and ability to determine extension of disease into the middle ear,” he said.

"Further, treatment is enhanced by the ability to flush more deeply into the ear and even reach the middle ear.

Robert Stannard, DVM, owner of Adobe Pet Hospital in Livermore, Calif., sees a lot of infections that have gone so wrong that owners have been advised that their pets need surgeries that risk deafness.

Dr. Stannard said scoping is one of the tools that enables him to save most of the pets from such a fate.

"We get the worst of the worst,” said Stannard, who also serves on the executive board of the American Heartworm Society. "Most of the time we are able to salvage these dogs.”

Many dogs have suffered ruptured ear drums from previous ear infections that have turned into infections in the bulla, the hollow cavity in the skull.  

"In a dog, it’s a big structure that can hold a lot of crud and corruption,” Stannard said. "A lot of the time veterinarians are trying to treat the outer canals, but without equipment designed to get down in there, video otoscopy, it’s pretty much inaccessible for most veterinarians.”

Stannard sees a lot of Gram-negative and pseudomonas infections. If they are not cleared before antibiotic treatment, it won’t affect those bacteria, he said. Stannard performs culture and sensitivity testing to determine what antibiotic will work.

He also cautions that many treatments are ototoxic and cannot be put in the ear if the ear drum is ruptured.

Steve Melman, DVM, a dermatologist and chairman of OtoPet-USA, also emphasized the need for cytology testing.

While allergies are the most common cause and must be diagnosed and treated simultaneously, Malassezia and bacteria can be diagnosed by simple cytology based upon a smear made from each ear, noted Dr. Melman. He said cytology testing must be done in every case.

"One problem with this diagnostic test is the variability of staining and quality of staining materials,” Melman said. "A simple slide-staining machine with variations to meet the reader’s needs should be a welcome addition to any busy practice.”

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