Bug off!

Ear mites cause both mechanical and chemical irritation, and often an allergic hypersensitivity reaction as well.

Might be a mite.

You’ve probably seen those ads on television for that flea and tick product that features an adorable Labrador puppy singing “ain’t no bugs on me.” Pretty cute, right? Well, little Newton looks just like that pup. His lucky owner also has an adult lab we have known for years, and the whole family visits our office regularly. When Newton arrived at eight weeks old for his initial examination, I was impressed by how thorough the breeder had been, evaluating the parent dogs for everything from hip dysplasia to a list of relatively uncommon genetic diseases, like exercise-induced collapse of Labrador retrievers.

“Wow,” I exclaimed. “I didn’t even know there was a test for that. Looks like Newton came from a really well-educated breeder.”

I noticed in passing that his ears looked a bit dirty but didn’t think much about it. Because her older lab has hip dysplasia, that was foremost in the owner’s mind, and our appointment time was spent focusing on discussing Newton’s hips. “He’s very mellow,” I commented, rolling Newton onto his back. “Let me check for an Ortolani sign.”

If you’re a mom of a human baby, you’ve probably seen a pediatrician do this maneuver.  Developed by an Italian physician named Marino Ortolani in the 1930s, it is a technique for assessing joint stability of the hips in infants. The same technique is used in puppies. With Newton on his back, I positioned his hind legs appropriately, then while gently pressing straight downward, simultaneously splayed his legs to each side, listening and feeling for a “pop” or “click” that might indicate laxity in the hip joints.

“They seem fine,” I said, “but the specialists advise doing this at 12 weeks of age. We’ll check him again next month.” We made a plan for his various vaccinations, dispensed heartworm preventative and flea and tick control and sent him on his way.

Four days later, his mom brought him back. “His ears are bothering him,” she reported. Now I know this owner well. She worries. A lot. But she is also very observant.

I lifted Newton’s ear. Well, whaddya know?  There were several scratches and scabs where the poor little fellow  had dug at his ears with his pointy puppy toenails. My assistant, Elise, had set out a microscope slide with a drop of mineral oil, her silent suggestion that I should check Newton for ear mites.

Really? I thought. Newton’s breeder had her dogs so thoroughly vetted, could she possibly have neglected something as basic as ear mites? But Elise was correct that any young animal with itchy ears should be evaluated for Otodectes.

Otodectes cynotis is a tiny mite that likes to live in the external ear canal of cats and, occasionally, dogs. Some veterinarians say they can see them with just the minor magnification of an otoscope, but my old eyes need a microscope. The mite is passed by direct contact between animals, especially from mother to babies, thus it most commonly infects young animals, although individuals of any age may be affected. In cats, up to 90 percent of all external ear infections are caused by ear mites. In dogs, most ear infections are bacteria or yeast related, but some may be caused by Otodectes. In either species, ear mites are highly contagious, making them particularly difficult to control in multiple cat households, catteries, and kennels. People exposed to ear mites have been reported to develop an itchy rash on the arms and trunk, but this is extremely rare.

Ear mites live on the surface of the skin and do not burrow. They feast on ear wax and skin oils. Their presence causes both mechanical and chemical irritation, and often an allergic hypersensitivity reaction as well. The characteristic debris consists of bloody crusts, skin, mites, and ear wax. Both ears are usually affected, but not always. Rarely, mites are found on other parts of the body, particularly the face, neck, lower back, and tail base, but they usually are confined to the ear. The resultant itchiness is often severe. In chronic cases, the eardrum may rupture and ear canals become scarred and thickened.

I swirled some of the dark, grainy debris from Newton’s ear into the oil on the slide and popped it on the microscope. Slightly embarrassed at having missed this simple diagnosis on his first visit, I waved his owner into the laboratory. “Come look,” I said, enjoying the expected squeal of disgust when she focused the scope on the wiggling eight-legged critters we just swabbed out of her pet’s ears.

There are a variety of medications that can be used to treat ear mites. In the old days, it often took three to four weeks of daily administration of available products to eradicate the little bugs. Nowadays we have many more choices, some applied topically, some orally, some by injection. I opted to use a product called Milbemite®, which we stock for use in cats. Although not officially approved for use in dogs, many vets routinely use it in canines as well as felines.  After getting the owner’s consent for this “off-label usage,” I squeezed a little tube of medication into each of Newton’s ears and massaged it deep into the canals. One treatment is supposed to kill all stages of the Otodectes life cycle.

It is usually advised to treat all the animals in the environment. Even if their ears look clean, they may be asymptomatic carriers, but in this case Newton had only arrived a few days previously. “Wash his bedding and keep an eye on your older lab,” I advised.

Two weeks later, Newton’s ears were improved but still a little irritated, so I prescribed a second medication that contained an antibiotic and an anti-inflammatory as well as a mitacide to be used for 10 more days. Good thing his owner paid attention to those ears and brought him back promptly.  I think Newton can now join in a chorus of “there ain’t no bugs on me.”