This is a story of a common skin complaint in young dogs, that often spontaneously resolves without treatment. The more chronic, severe form can leave a dog looking like something off the streets of the Third World, and fearing the social stigma of owning a mangy dog compels most pet owners to use insecticidal medication that may not be necessary. There’s a variety of treatment options that vary in cost and ease of administration.
Mother and infant Demodex under 100x magnification, in a skin scraping. Black line is a hair shaft
Torpedo shaped, the 8-legged, microscopic demodex mite lives in the follicles and sebaceous glands of the dog. It eats dead skin and reproduces, although population growth is suppressed by a healthy, well-nourished immune system.
In preparation for transmission to puppies, mite numbers soar during late pregnancy. Whether or not this is response to detection of the hormones of pregnancy, the immunosuppression of progesterone, or nutritive depletion and metabolic drain of a full womb and lactation, remains uncertain.
Within 3 days of birth, all puppies have caught this mite from mum; maybe from nipple to lips, or just the intimate skin contact of group cuddles. Like a microscopic herd of skin-eating Buffalo, the population grows and gradually migrates, colonising follicles all over the bodily landscape. Favoured habitats seem to be face, neck, skin folds and between toes.
Demodex canis grazing on skin and 3 burrowing, head-first down a hair follicle
During the first 18 months of life, skin symptoms may erupt if the immune system has difficulty suppressing mite numbers. This may be just immunologic immaturity, something the dog will grow out of; a nutritional/environmental factor; or a genetic deficiency, with certain breeds well-known to be predisposed (Dalmatian, Staffy, Boxer)
The classic presentation is patches of thinning hair or baldness, usually non-itchy, sometimes with scabbing and folliculitis, often starting around the eyes, face and neck, and occasionally extending over to the body and limbs.
If the skin lesion is small and non-progressive, a pet owner may be able to just monitor and avoid treatment. Ensuring the dog is on a well balanced, high quality diet may help, and there may be some response to immunostimulatory supplementation.
The lesion may spontaneously regress after a month or two. Irrespective, many vets will recommend treatment of this mild form of the disease, as it’s difficult to predict which will progress to the more extensive, severe form described below.
At a distance, Arnie, pictured below, looks a picture of health. On closer inspection there are patches of hair loss, not only over the temples, but also similar lesions were starting to erupt over the neck and body. Arnie is looking for a home, by the way, and don’t be put off by his temporary dermatologic setback. The hair will regrow with treatment.
Generalised, Interdigital, Skinfold, and Adult-onset Demodectosis
If, however, the lesions begin to spread, all vets will recommend using insecticidal agents for a few months or more. The goal is to knock-down mite populations, and buy time until the immune system learns how to control the mite itself. We are not aiming to cure the dog of the mites altogether.
A small number of dogs suffer a permanent defect in their immune system and will need to be on insecticides for extended periods into later life. However, with the smorgasbord of modern insecticides on offer there days, this isn’t as problematic as it once was.
Use of immunosuppressive drugs (cortisones, cyclosporin, azathioprine, chemotherapy) in dogs with allergies or other diseases will sometimes sufficiently dampen immune function to allow demodex to flourish, and in such cases vet and pet owner may be forced to weigh the costs of one disease against another, or resort to adding insecticide to the list of daily medications. More of the demoralising cycle of controlling the side effects of one drug with another, here.
Many of the tragically thin and sickly street dogs, living all around the developing world, suffer demodectic mange. The stress of malnourishment and fighting for survival depletes the immune system and allows mites to proliferate.
1. Amitraz is an old-school organophosphate treatment. Made from a concentrate and poured over the dog twice weekly, it’s cheap and often effective, although fallen out of favour in recent years. It’s laborious, mildly toxic to you and the dog, and makes the house smell of an industrial chemical plant. A side benefit is control of ticks and fleas during treatment. About 75% of mange cases respond to this agent.
If your dog suffers stubborn interdigital demodex (paws), training him to stand in a foot bath of this stuff is a good way to strategically hit the insect with minimal toxic load to the dog.
Damage: liver, see Tick Prevention: Cost versus Benefit.
2. Ivermectin is a liquid agent, registered as a wormer for cattle and sheep, but can be given to dogs once daily, by mouth. With the exception of Collie breeds which suffer a genetic problem with this family of drugs, it’s usually side-effect free, easy to give, inexpensive, and odourless. Success rate above 90%. It’s safe enough that we may double the initial dose if the mange is progressive, despite treatment.
Damage: transient neurologic effects in susceptible breeds.
3. Doramectin is a longer-acting agent in the same family as ivermectin, given as weekly subcutaneous injections by vet, or pet owner if experienced and confident with such procedures. This may be more convenient for some dog owners, and often favoured by vets who like the weekly revisits to monitor progress.
Damage: transient neurologic effects in susceptible breeds.
4. Milbemycin Oxamine (Interceptor®, Sentinel Spectrum®, Milbemax) is a monthly, oral worming, heartworm and flea preventative that, when given daily at high doses, is very effective at controling demodectic mange. The problem? Not toxicity, it’s very safe. Priced as a drug given monthly, it’s only really affordable for the super-rich, pharmaceutical company employees, or when a whole pallet of the product goes over used-by-date. This happened in Sydney in the 1990’s, and Ciba Geigy generously treated demodex in dogs whose owners would never have been able to afford such gold-standard medication.
Damage: financial, severe.
5. Advocate® is an over-the-counter monthly spot-on treatment that kills fleas and controls heart and intestinal worms. Containing Moxidectin, it has some activity against the demodex mite. I wouldn’t recommend this for the severe, generalised form, but may be of use for owners of dogs with mild forms of the juvenile disease, or monthly for life for those dogs with genetic susceptibility in adulthood.
Damage: financial – moderate in the short term if used in juvenile form; more severe if used monthly for life in adult demodex.
6. Holistic support – dietary supplements, fish oils, and neem ointments and shampoos, a natural, plant-based insecticide. Here is a commercial site that reports spectacular response to such treatments.
Treating Secondary Problems
Secondary bacterial infection may occur, manifesting as scabs and pimples, and may demand antibacterial shampoos (keratolytics like benzyl peroxide are a good choice) or oral antibiotics (cephalexin is a good, inexpensive choice).
If the dog is itchy, try using antibiotics and always avoid cortisones. These drugs are useful for supressing hyperactive immune states, like allergy, but counterproductive in infections – microbial or insect. Mites love cortisone.
Similarly, if your dog develops patchy hair loss that looks just like the usual seasonal allergy, but gets worse on cortisone medication that worked so well previously, it may be proliferation of mange mites. Request a skin scrape!
Diagnosis and Treatment Duration
Skin scrapes are the easiest way to diagnose and monitor response to treatment. Painless to collect, they are cheap and easy for GP vets to examine under a microscope, in-house. Weekly skin scrapes are taken after 1 month of treatment. Insecticidal medication ideally continues until 2 weeks after the second negative skin scrape (no mites seen), resulting in at least 2-3 months of treatment.
- This is not a contagious disease. If your healthy dog hangs out with, or even cuddles a mangy dog, there is no risk of transmission. Mites may move between them, but the immune system of the unaffected dog will limit proliferation of new demodex invaders.
- If your juvenile dog develops a small patch of hair loss on the face, don’t freak out. Watch it, look for more, including patches of hair thinning most easily seem under bright sunlight. If a patch of hair loss remains solitary, and then gradually fills in, nothing needs to be done. If more erupt, especially if spreading down the body, involve a vet.
- If your dog develops chronic demodex in adulthood, in the paws, facial folds, or more extensively, use stronger insecticides initially, then try to maintain remission with holistic treatments or Advocate®.
- There is a genetic predisposition to demodectic mange. If you know of close canine relatives (parents, siblings) that have suffered the severe, generalised form, then it may be best to aggressively treat early symptoms, rather than waiting to see if it’s going to spontaneously resolve. Certainly don’t breed from dogs who suffer the severe form.
I have seen generalised domedex in a a cat with Feline Immunodeficiency Virus (FIV), and I expect other causes of malnutrition or immune depletion could also result in this canine mange in a feline.
Mange mites have been detected on humans, surprisingly enough in the eyebrows, but are not usually associated with dermatologic disease.
Tags: Advocate, allergy, alopecia, amitraz, avermectin, bacterial, canine, cat, chemotherapy, Collie, cortisone, dectomax, demodectosis, demodex, dermatology, disease, dog, doramectin, folliculitis, hair loss, immunosuppression, infection, insecticides, interceptor, interdigital, itch, ivermectin, ivomec, mange, milbemycin, moxidectin, neuro, OP, organophosphates, paw, pododermatitis, prednisone, scabs, scrape, skin, skinfold, toxins, vet, veterinary, zoonosis