Thursday, May 23, 2013

By Michelle Gerhard Jasny V.M.D.
Published: July 16, 2009

"Someone on the phone wants to know if she can catch ear mites from her cat," my secretary announced. That was a new one. I've been asked about the zoonotic potential of everything from ringworm to Lyme disease, but no one has ever asked about ear mites before. (A zoonotic disease is one that can be transmitted from animals to people.) I paused, wondering what nasty symptoms the caller might be experiencing to elicit this query, or if it was just idle curiosity.

Otodectes cynotis. From Latin for "biter of the ear." Ear mites are members of the Arachnida class, which includes spiders, scorpions, and ticks, as well as mites. Although some people claim to be able to see them with the naked eye, this ability has always eluded me, even in my pre-bifocal days, but I love to scoop a hunk of classic "coffee grounds" debris from the ear of some head-shaking kitty, mix it with a drop of oil on a slide, pop it on the microscope, and say "Wanna see why Mighty Joe is scratching?" "Sure," replies the innocent owner, who ambles over to the scope, then lets out a gasp or an "eeewwwww" as she gazes down at dozens of active, creepy, six-legged critters swimming around on the slide.

The ear mite has an unusual lifecycle. Eggs hatch into larvae that feed on earwax and skin oils. After a week, these molt and become protonymphs. They keep eating, then molt again into deutonymphs. Here's where it gets strange. The deutonymph, which as yet is neither male nor female, mates with an adult male mite. It is only after mating that it goes through a final molt, which determines its gender. If it turns out female, then she is already pregnant with fertilized eggs from that mating. If it turns out male, nothing happens, and it may go on to breed with other deutonymphs. The entire lifecycle takes three weeks. Otodectes mites do not burrow under the skin but are still extremely irritating, causing inflammation and predisposition to secondary bacterial and yeast infections. Most mites stay inside the ears, but may occasionally spread to the head or face.

The majority of all feline ear infections are caused by mites, which are passed from infected mother to kittens or between adult cats in the course of cuddling, grooming, or close cohabitation. Affected ears are filled with characteristically dark, dry, granular debris and are usually intensely itchy.

Dogs are a different story. Owners often erroneously assume their pups' ear problems are caused by mites, but in fact, ear mites account for very few of canine otitis cases. The majority of doggy ear infections are caused by bacteria and/or yeast and require an entirely different treatment than a mite infection. That's why that "ear mite remedy" you got at the pet store isn't solving Fido's problem.

Effective mite treatment requires thorough ear cleaning, followed by appropriate medication for all exposed pets. If it really is mites, that pet store remedy will probably work - but only if applied daily for a month. (Since most OTC products do not kill the eggs, treatment through a complete lifecycle is needed to truly knock out the infestation.) Then there is the prescription medication Tresaderm, which veterinarians have dispensed for decades. A 10-day course is usually sufficient to eliminate mites and has the added advantages of containing an anti-inflammatory and treating secondary bacterial and yeast infections. The down side is that you have to refrigerate it, and Mighty Joe may find those ice-cold drops mighty annoying. Ten days is easier than 30, but still a major hassle for pet owners, leading to poor compliance.

Nowadays there are easier options. Acarexx contains ivermectin, a drug with a multitude of uses ranging from horse wormer to heartworm preventative to mange treatment. A single dose applied in the ears is touted to eliminate Otodectes infections, though I usually retreat in three weeks, just to be sure. MilbeMite is a similar single-application product, which contains milbemycin, the ingredient in the heartworm preventative Interceptor. Both products are FDA-approved for use in cats and kittens only, although many veterinarians also use them to treat dogs.

But what if you have a pet like Benji, a Chihuahua recently adopted from a rescue operation? Sweet as can be with his new owner, he won't let me get near him. I checked his ears recently while he was under anesthesia for a dental cleaning and found ear mites. I gave the first treatment while he was snoozing, but three weeks later, Benji wouldn't let anyone mess with his ears, not even his new mom. And there's nothing scarier than a really mad Chihuahua. For Benji situations, some of the "pour-on" flea products designed to be applied to the skin along the back such as Revolution and Advantage Multi are also effective against ear mites. We might not be able to get medication into Benji's ears, but his mom was able to squirt a tube of Revolution on his back.

What if you keep treating Mighty Joe for ear mites, but he isn't getting better? Have your veterinarian confirm ear mites are truly the problem. Then look at the big picture. Sometimes other pets are asymptomatic carriers, serving as a constant source of reinfection. You have to treat all the household pets. You may need to try a different product. In a few cases, you may need to do environmental treatment. Although ear mites typically stay in Joe's ears, they can persist briefly in areas where pets sleep and hang out.

Human infection? It has been reported but is extremely rare. But take another look at that microscope slide. Those creepy, crawly mites will convince you Mighty Joe deserves effective, immediate treatment - especially if you're sharing a pillow.