Demodex mites are a common cause of hair loss, redness and crusting in young dogs whose immune systems are still developing, as well as older dogs and cats with an underlying immune abnormality. Listen to this week’s episode to hear where these mites come from, what problems they cause, how they can be treated, and why they are Dr. Lancellotti’s favorite parasite.
Introduction to My Favorite Mite
[00:01:06] Welcome everyone to today’s episode of Your Vet Wants You to Know. On today’s episode, I’m going to tell you about one of my favorite parasites. No, I’m not referring to my children, God love them. I’m referring to a mite called demodex. If you’ve listened to some of the other episodes of skin diseases, particularly allergies and Cushing’s disease, you probably know that most of the pets I treat have lifelong conditions that need long-term treatment. I like this aspect of veterinary care because it gives me the opportunity to really get to know the pet owner. We share in frustrations and successes over many years, working together to find the best treatment for their pet. Demodex and the skin problems that they cause are a special treat for me because, for most animals, it gives me the opportunity to actually cure the skin disease rather than just manage it.
A single Demodex canis mite on the end of a hair viewed under the microscope.
[00:01:56]The other reason I love demodex is because of their unique structure, which you can see pictures of on the Your Vet Wants You to Know website. They are cigar shaped microscopic mites that have four pairs of really short legs towards the front half of their body. What’s special about demodex is their digestive tract, which has an entrance at their mouths, but does not have an exit because they lack an anus. This lends itself nicely to the expression, “Demodex doesn’t give a crap,” mostly because they can’t, making it my favorite mite.
A single Demodex injai mite viewed under the microscope.
Demodectic Mange/Demodicosis
[00:02:28]Demodex mites are the cause of demodectic mange or demodicosis. Now I know when you hear demodectic mange, you might think of a dirty mutt roaming the streets, but that’s just because you’re listening to this podcast and seeing the artwork for Russell Sprout the dirty mutt that I found wandering the streets during vet school. Demodex mites, which cause mange, are actually present on all dogs, even the Bellas of the world with their perfectly coiffed fur and pink bow, fresh back from a spa day. Humans have their own species of demodex mites on us as well. They’re typically a part of the normal microorganism population that usually lives in harmony on the surface of the skin. Puppies get these mites from their mother when they’re nursing and for the overwhelming majority of dogs, the mites cause no problems whatsoever, unlike toddlers, who usually cause problems constantly. Now, normally the immune system, which protects the body from infections, keeps the population of demodex mites so low that they don’t cause a problem on the skin. When the demodex mites do overpopulate, they cause a skin condition called demodectic mange or demodicosis.
Juvenile Onset Demodicosis
[00:03:34] There are two different situations in which a dog might develop demodectic mange. In puppies, just like every other body system, the immune system is still developing. So sometimes the demodex might take advantage of that immature immune system and use that opportunity to overpopulate. And as a result, demodex typically causes problems within the first 18 months of a puppy’s life. This is called juvenile onset demodicosis and that’s the most common reason to see demodex.
Puppy with hair loss on its back from juvenile-onset demodicosis.
Adult Onset Demodicosis
Sometimes demodex mites can cause problems in older dogs too. This is referred to as adult onset demodicosis. Usually when this happens, there’s something going on with the dog’s body that’s affecting their immune system, such as Cushing’s disease, which Dr. Amy Oberstadt and I talk about in previous episodes, as well as hypothyroidism, certain cancers or treatment with medications that affect the immune system like steroids or Apoquel. If I see an older dog develop demodex mites, I’m definitely going to have a conversation with the pet owner about trying to figure out what’s going on with the pet’s immune system that allowed those mites to overpopulate. Less commonly, we can see demodex mites in cats, usually a result of some other disease that affects their immune system also. In cats, things like feline immunodeficiency virus, or FIV, diabetes, or lymphoma can predispose them to demodex. In cats with demodicosis, just like in dogs with adult onset demodicosis, I would recommend working with your veterinarian to figure out why that cat’s immune system isn’t working properly.
Older dog with red, swollen, itchy paws from demodicosis.
Clinical Signs
[00:05:09]So let’s talk a little bit about what things you might see if a pet has demodex mites. There could be a pretty big range of severity with some animals experiencing only a small patch of hair loss, which we call localized demodicosis. Other animals have really severe disease that affects their entire body, which we’ll call generalized demodicosis. These animals have large crusts, redness, blackheads, which we call comedones and pustules on their paws, their belly, their face, their back, essentially anywhere. These dogs may have a secondary bacterial infection also because of the damage the mites have caused to the skin. The more severe the skin disease is, the more likely the pet is to show signs of illness, such as low energy, weight loss, and fever. They really just don’t feel well. One particular species of demodex mite likes to live on the back of certain dog breeds like terriers or shih tzus , and these dogs have super greasy hair and skin on their backs as the biggest sign of infestation.
Crusting, hair loss, secondary bacterial infection in a dog with severe juvenile-onset demodicosis. This dog also had a poor appetite, weight loss, and lethargy as a result of systemic illness.
[00:06:09]In cats with demodicosis, you can have crusting, redness and hair loss. With certain species of demodex, these cats are intensely itchy to the point of over grooming most of the hair from their body.
Cat with redness, crusting and hairless in an area of demodicosis as a result of steroid inhaler use. Image courtesy of Dr. Alicia Webb-Milum, Redbud Animal Dermatology, Allergy, and Ear in Oklahoma City
Diagnosing Demodectic Mange
The good news is diagnosing demodex is fairly straightforward and simple. The most common method for diagnosing these mites is called a skin scrape. It’s essentially what it sounds like. I’m going to take my fingers and gently pinch the area of the pet’s skin where I think there might be mites. As I’m doing this, I’m using my imagine-o-scope, and just to let you in on a secret, the imagine-o-scope isn’t an actual instrument, it’s just my imagination. But I’m going to use that imagine-o-scope to visualize mites being squeezed up and out of the hair follicles, where they like to infest. Then I’m going to take an actual scalpel blade with some mineral oil, and I will gently scrape the surface of the skin to capture those mites and then place that material on a slide for me to look at under a microscope. This doesn’t hurt the dog or the cat. It should actually feel like a really nice scratch for them but it may leave just a little bit of a raspberry. I want to mention just how important it is for me that pets are comfortable when I’m collecting samples and doing my exams. So I am a Fear Free certified veterinarian and speaker, and that means that I’ve gone through additional training in order to help minimize fear, anxiety, and stress in the pets that I’m treating. I also help to teach other veterinary professionals these techniques at lectures and conferences. I have a really great video of Jack the puppy, who’s getting a skin scrape done while being distracted with a chew toy. This little puppy has absolutely no idea that I’m doing any testing on him whatsoever. He is just as happy as can be gnawing away on that bone. So the skin scrape really isn’t as bad as it sounds. You can check out video of Jack if you’re worried about how painful a skin scrape might be. I’ll have videos of him on the website as well as on our Facebook and Instagram.
Jack the puppy chews happily on a treat while a Fear Free skin scrape is performed to identify demodex mites as the cause of his hair loss.
Sometimes if a pet is too painful to do a skin scrape, which is possible because in these really severely affected animals, demodex generally causes more pain than itchiness, or if the area that I’m worried about is in a really sensitive part of the body, like around the eyes, there are some other ways that I can find mites without stressing out that pet. That includes things like plucking the hairs to see if there are mites at the base of the hair where they like to live, or using scotch tape to capture the mites from the surface of the skin after I’ve squeezed them up and out from the hair follicles. Because demodex can lead to secondary bacterial infections, also I’ll generally perform what’s called a cytology to look for bacteria. Cytology involves me pressing the slide directly onto the animal’s skin, and then looking under the microscope for what’s there. I’ve got a great upcoming episode with a fellow dermatologist, Dr. Ashley Bourgeois all about cytology, so make sure you’re subscribed to the podcast so you don’t miss that episode. Overall, very simple, non-invasive relatively inexpensive tests to tell me what’s happening quickly so I can start treatment.
A hair pluck is performed on a dog with hair loss from demodex around its eyes.
Treating Demodectic Mange
[00:09:20] In the past decade, a new class of flea and tick preventatives has come out that has been shown to be highly safe and effective against the treatment of demodectic mange. This class, called the isoxazolines, includes medications, such as Simparica, Bravecto, Nexgard, and Credelio. We have the most scientific evidence for the efficacy of Simparica and Bravecto for the treatment of demodex mites, but the other two medications in this class have evidence to support they work just as well. None of the studies looking specifically at the use of isoxazolines for the treatment of demodex have had any reported side effects. It should be noted that the FDA advocates caution with the use of these medications in dogs that have a history of seizure disorders or epilepsy as they can potentially lower the seizure threshold
A tape prep is performed on a dog with hair loss around its eyes to identify demodex mites.
[00:10:11] I want to address the use of this medication in a certain breed of dog that historically has been more susceptible to having adverse effects from flea and tick preventatives. So one isoxazoline in particular, Bravecto, has been specifically studied in Collie breeds that have a genetic mutation in the MDR1 or ABCB1 gene. This mutation makes these dogs more susceptible to certain medications having adverse effects. In this study, even at three times the recommended dose of Bravecto, there were no observed adverse effects in these dogs. That’s especially exciting because prior to this class of medications coming out, there was a significant risk associated with treating demodectic mange in these breeds because the dogs have this mutation. There are there treatments that have been evaluated for the treatment of demodectic mange and were used commonly before the new class of flea and tick medications came out. These other treatments have not been shown to be as rapidly effective or as safe as medications like Simparica, Bravecto, Credelio, or Nexgard.
Demodex mite and lots of white blood cells with secondary bacterial infection on cytology from the skin of a dog with demodicosis.
[00:11:14]If there is a secondary bacterial infection, this should be treated in addition to treating the mites. Depending on the severity, there’s good evidence that most secondary bacterial infections can be treated just with medicated bathing and other topical therapies like medicated spray, or medicated mousse. As a veterinary dermatologist, I see a lot of multi-drug resistant bacterial infections from chronic antibiotic use. I’m always trying to use antibiotics only when I have to and focusing more on topical treatment to address the infection. Sometimes animals are really severe though, and I may need to use an additional oral antibiotic in addition to the medicated bathing for those really deep infections.
[00:11:56]For some young dogs that have really mild signs, like just a small patch of hair loss, you may not even need to treat them because as their immune system matures, the disease resolves on its own. For older dogs or cats that have demodex, in addition to treating the mites, it’s important to work with your veterinarian to investigate what’s going on with your pet’s immune system that allowed those mites to overpopulate in the first place.
[00:12:19]Research has shown there is a link to severe generalized demodicosis in puppies and a genetic abnormality in how the immune system develops in those dogs. Because of that genetic link, it’s really not a good idea for puppies who have had generalized demodicosis when they were young to go on and have puppies of their own. We recommend that those dogs not be bred.
[00:12:42]Occasionally dogs will get really, really itchy within the first few days of treatment as those mites start to die off in the hair follicles. They can make the animal intensely itchy. So while I had mentioned before that steroids could actually lead to the development of demodex, in this small, short period of time, the use of steroids can actually be a relief for these dogs. So we may give them just a few days of steroids to decrease the inflammation and provide some relief as the might start dying off. But we don’t intend to use the steroids long-term because this disease to response really nicely to treatment.
Follow up until cured!
[00:13:17]We typically classify a cure based on the clinical response to treatment. So we want to see the skin starting to look better as well as negative skin scrapings. So it’s important that as your animal is being treated, that you follow up with your veterinarian so that they can do those skin scrapes to make sure that even if your animal’s starting to look good, that the mites are dying off as well and there’s no additional treatment that may be needed. Long-term a lot of pet owners do decide to keep the pet on this particular flea and tick preventative that also treats for demodex because they need excellent flea and tick coverage as well. This class of medication does provide that. If you want to switch to something different, talk to your veterinarian about what options are available for long-term parasite control.
[00:13:59]If you want to see pictures of pets that have demodex to kind of get an idea what that looks like. You can visit the website, www.yourvetwantsyoutoknow.com. You can also follow us on Facebook and on Instagram, to see video of Jack, getting his skin scrape done, as well as dogs and cats that have demodex.
[00:14:20] If your pet has had demodex or any other type of skin condition, and you just want to commiserate with some other pet owners, you can join our Facebook group, Your Vet Wants You to Know and share stories about what you’ve been through.
[00:14:32]I like to close each episode with a segment, I call “Scratching the Itch”. The segment is designed to highlight something, whether it’s a product, a website, a story that provides a relief or just makes you feel good. Hence, scratching the itch. After the last episode where I spoke with Dr. Donny Consla about when it’s time, I started thinking a lot about a place that is very special to me. I did some of my training, both in veterinary technician school, as well as in veterinary school at a place called Best Friends Animal Sanctuary in Kanab, Utah. This place is about 3,700 acres, and at any given time, this sanctuary houses about 1,700 animals, dogs, cats, birds, horses, pigs, rabbits, goats, wildlife, lots of different species of animals have found sanctuary in Best Friends. There’s a very special place at Best Friends called Angels Rest. Angel’s Rest is one of the most peaceful places I’ve ever been in my whole life. Angel’s Rest provides a final resting place for sanctuary animals and beloved pets of Best Friends members and staff. It’s hard to truly describe how serene this place is. There are wind chimes everywhere and memorial markers for all the pets that are there. You walk through these beautiful wrought iron gates and you just feel at peace. You feel the love that all of these pets have given to their families.
[00:16:06] Just when you feel completely overcome with sadness and with loss, the wind will slowly start to move the wind chimes and are all around you. You are surrounded by this beautiful melody. That just sounds like love. The wind chimes provide a beautiful Memorial and a constant reminder that these animals were there for us.
[00:17:06] I’ll have a link where you can find more information about Angel’s Rest at Best Friends in the show notes for you. They hold a monthly blessing to honor the sanctuary animals that have passed as well as staff and member pets that have crossed the Rainbow Bridge. Best Friends offers lots of different ways that Angel’s Rest can provide you with a Memorial for your pet.
[00:17:29] If you ever get the chance to go to Kanab, Utah, I highly recommend taking a moment to go to Angel’s rest and feel the spirit of the animals surround you while you listen to the wind chimes. It truly does make you feel good.
[00:18:06] If you have something you would like featured in the “Scratching the Itch” segment, you can contact me through our website or through the Facebook group.
[00:18:21] That’s all for today’s episode. I look forward to your next visit with Your Vet Wants You to Know.
References:
- Bond, Ross, et al. Diagnosis and Treatment of Demodicosis in Dogs and Cats Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. VETERINARY DERMATOLOGY, vol. 31, no. 1, p. 27–+.
- Bowden, Daniel G., et al. Canine Demodicosis: A Retrospective Study of a Veterinary Hospital Population in California, USA (2000-2016). VETERINARY DERMATOLOGY, vol. 29, no. 1.
- Perego, R., Spada, E., Foppa, C. et al. Critically appraised topic for the most effective and safe treatment for canine generalised demodicosis. BMC Vet Res 15, 17 (2019).
- Pereira, A. V., et al. Comparison of Acetate Tape Impression with Squeezing versus Skin Scraping for the Diagnosis of Canine Demodicosis. AUSTRALIAN VETERINARY JOURNAL, vol. 90, no. 11, pp. 448–450.
- Xueying Zhou, et al. Review of Extralabel Use of Isoxazolines for Treatment of Demodicosis in Dogs and Cats. Journal of the American Veterinary Medical Association, vol. 256, no. 12, June 2020, pp. 1342–1346.
