I’m going to sneak in a “by request” post this week. I didn’t have an opportunity to photograph a spay procedure on Wednesday, but as soon as I can get an image set together, I’ll post that. The topic today will be “mites.” While there are a ton of different mites, I’m going to show you the three we deal with most commonly. The first two are seen primarily in dogs, and the third in cats.
Demodex (Red Mange)
Demodex mites (Demodex canis) are allays found in the skin of dogs in small numbers. They live in the hair follicles and oil glands. Humans have a couple of varieties of mites, too, that live in eyelash/eyebrow follicles. People and dogs don’t trade Demodex back and forth. Dogs generally don’t infect one another with mites, either. The body usually keeps the population under control so that there aren’t any problems. In some patients, the immune system can’t keep the mite population under control. When mites overpopulate, they damage the hair follicle. Hairs fall out, causing bald patches (usually a circular spot). These patches really aren’t itchy at first. However, the follicles are damaged and inflamed, so secondary infection sets in. This bacterial infection causes a lot of itching, swelling, scabbing, and oozing. Dogs can have these small spots spread all over the body, too. That’s called Generalized Demodicosis. Here are some pictures of the mites and the skin of an affected dog. Notice the cigar-shaped body of the mite.
We diagnose Demodex taking a scraping of the skin to examine under the microscope. We apply a little mineral oil to the skin, squeeze the skin to push the mites out of the follicles, then scrape the skin with a special little spatula. We have to scrape deep enough to get some bleeding: it ensures that we’ve obtained material from inside the follicles where the mites hide. We examine that under a microscope to look for mites or mite eggs.
Demodex is treatable. The spots of hair loss can be treated with an ointment called Goodwinol. It contains a naturally substance called rotenone that kills Demodex mites. (Interestingly, rotenone is used by indigenous tribes to kill fish for food.) Dogs that have the generalized form have to have special baths/dips with a drug called amitraz. Amitraz does have some side effects: drowsiness, drooling, and loss of appetite. Most are very temporary. If they’re severe, they can be treated with an antidote. Treating generalized Demodex can take months. Some patients need to have dips forever to keep the infestation controlled. Alternative treatments include use of ivermectin or milbemycin (the ingredients in heart worm prevention) on a daily basis for 3-8 months.
Cats have their own type of Demodex. We treat much the same as in dogs. I think I’ve only seen one or two cases of this in the last 7 years at Pet Authority.
Sarcoptes (Sarcoptic Mange)
Sarcoptes scabei is a very different problem than Demodex. These mites are highly contagious, so affected animals can give mites to animals contact. Boarding facilities, kennels, groomers, and the vet’s office are common places for exposure. Two to six weeks pass before dogs show signs of infestation. The mites burrow through the skin, leaving behind substances and eggs that cause dogs to have an allergic reaction. Affected dogs are insanely itchy. They literally can’t do anything but itch and scratch and chew. Their hair falls out, the skin gets crusty, may have a rash, and both dogs and owners are miserable. The most common sites for lesions are the ears, elbows, and hocks (ankles).
Here are pictures of the mites and the skin damage they cause. That’s a red fox, which normally has a fluffy tail and bright orange hair coat. The poor guy is a mess! Dogs look this way or worse when they have scabies.
We diagnose Sarcoptes by attempting a skin scrape. Scrapes are not done as deeply as when we’re looking for Demodex. Scrapes find Sarcoptes only 50% of the time. This is one of the very diseases we diagnose and treat based on the examination and history.
This is a zoonotic disease! You can catch sarcoptic mange from your dog. The rash is usually in a limited area, and as long as the dog is treated, the human infestation will go away without treatment. Sometimes people do require treatment by a dermatologist.
Treament is very easy. There are topical medications (Revolution/Selamectin), injections (ivermectin), dips (amitraz and lyme sulfur), and oral medications (milbemycin). Most patients are cured within a few weeks. We also treat patients with antihistamines and steroids to reduce the itching.
Otodectes (Ear Mites)
This mite affects cats more than dogs. Ear mites are officially named Otodectes cynotis. They live in the ears and cause intense itching. They also leave behind a very crusty, sticky black material that is distinct from other types of discharge we see in ears. These mites are highly contagious among cats and from dogs to cats or vice-versa. If a household has more than one pet, all of them need to be treated. Fleas can also carry mites and eggs from pet to pet and into the environment.
The mites are visible with an otoscope when we examine the ears. We take a q-tip sample from the ear and inspect the debris under the microscope. It’s easy to see these mites. They’re similar to the Sarcoptes mites in appearance. Thankfully, these are easy to diagnose. Here’s a picture of the mites and the ear discharge.
Otodectes are easy to treat. Topical medications (moxidectin, selamectin, ivermectin) are all very efficient at killing these mites. We to treat for 3-6 weeks. The only trouble is that these mites can live in the environment, and once in a while they are found on the animal’s body as well as in the ears. The topical medications we use for flea control work for treating mites anywhere on the body. Environmental treatment is also advised, which includes vacuuming/washing and application of an insecticide.
That’s the tour of the microscopic critters that can infest pets! It’s honestly one of the grosser things to investigate. Parasites are exceptionally good at doing what they do. In a clinical way, it’s fascinating, but it’s also enough to keep you awake at night! The best way to prevent all of these disgusting passengers on your pets is to keep them healthy and protected by a topical flea prevention and/or flea/heartworm prevention product.