Ringworm in Dogs

Symptoms, Causes and Treatment of Ringworm in Dogs

This article is written by Pet Circle Veterinarian, Dr Carla Paszkowski BVSc.

Ringworm (also called 'dermatophytosis') is a fairly common causes of skin infection in dogs all over the world. Causing skin lesions on most mammals (including humans), this irritating infection is usually worst in the young or immunocompromised. Puppies, children, and allergy sufferers (both canine and human) are usually the worst affected by ringworm. Thankfully, the issue is easily treated and doesn't cause serious disease unless a secondary germ takes advantage of the infection.

Is ringworm a worm? Despite its name, Ringworm is not a worm! Ringworm is actually caused by a fungus. (Perhaps it would be better named 'Ringus'!) The only thing it has to do with rings is the typical circular area of dry, scaley rash that usually appears on the animal.

Jump to a section:
1. What is Ringworm?
- How do dogs get ringworm?
- Dog ringworm in humans
2. Symptoms of Ringworm in Dogs
3. How to Treat Ringworm in Dogs
- Does Advocate treat ringworm in dogs?
- Product list - best ringworm treatments for dogs available online

What is Ringworm?

Despite the name, Ringworm is not actually a 'worm', but a fungus. (Perhaps a more fitting name would be 'Ringus'!). When we talk about 'ringworm', we are usually referring to the infection caused by the fungus, rather than the fungal organism itself.

The fungal pathogen responsible for ringworm is a commensal organism found on healthy skin, but only causes disease when it grows in too great a quantity, or if the skin or immune system is comprimised and can't fight it off. The pathogen that causes ringworm is also responsible for 'athlete's foot'.

In dogs, about 98% of ringworm cases are caused by a species of fungus called Microsporum canis, however it may be caused by any species of Microsporum, Nannizzia, or Trichophyton fungi.² These types of fungi are invisible to the naked eye, but looks a little like this under a microscope:

Source: James Scott, University of Toronto, via Medmyco at English Wikipedia

How do dogs get ringworm?

The Ringworm fungus spreads easily in the environment. It is primarily spread via contact with an infected host (be it canine, human, or another mammal such as a cat) and by touching contaminated objects like furniture, towels or grooming tools. Broken hairs that contain the fungal spores are a common source of spreading ringworm, and spores may survive in the environment for up to a year.¹

As with many diseases, direct contact does not always result in infection. The development of lesions depends on host factors - particularly age, immune system health, skin quality, hygeine, and nutrition. This is why the disease is commonly seen in puppies, pregnant dogs, or those with skin allergies. Likewise, children, pregnant women, the elderly, and immunocompromised people (such as those with HIV or eczema) are more commonly affected.

Where did my dog catch ringworm? As stated previously, the Ringworm fungus is a commensal organism that grows on the skin naturally, so your dog may have been exposed anywhere or from anywone. However, dogs are often exposed to larger quantities of the fungus in environments such as a shelter, dog kennels, pet store or breeder - which may concurrently be a stressful environment for your dog and therefore compromises their already fragile immune system.

Dog ringworm in humans?

Ringworm is transmissible between pets and humans. While dogs can transmit ringworm to humans, in fact, many dogs are actually infected by children in the household who have been infected at school or day care. (And unfortunately, often the dog is blamed for passing it to the child, rather than the other way around!)

If you or your child has been diagnosed with ringworm infection, don't panic - the disease is fairly easy to treat. (See our treatment section below)! You certainly shouldn't get rid of your dog or remove them from your house temporarily - this may only stress your dog and therefore make them less likely to recover.

Remember that a strong immune system can usually fight off ringworm fungus on its own, so never under estimate the power of good nutrition, rest, probiotics for dogs, and Omega fatty acids (such as fish oil) alongside medical and environmental treatment!

Symptoms of Ringworm in Dogs

Ringworm usually produces red, inflamed, ring-like lesions with a scabby or bald centre, or thumbprint-shaped scabby lesions. However ringworm can also present as generalised, dry, scaly, or sparsely haired skin. In dogs, it can affect the skin over any part of the body. In humans, lesions usually present as ring-like or thumbprint-shaped red lesions. In both dogs and humans, lesions may or may not be itchy.

How to tell if my dog has ringworm? Ringworm needs to be diagnosed by a vet before choosing a treatment. This is particularly important because some bacterial infections and parasites can appear similar to ringworm but require a different treatment. Demodex mite lesions, for example, can look almost identical to ringworm lesions.

To diagnose ringworm, your vet may do a microscope examination of your dog's skin scraping or fur, and they may also use a Wood's Lamp to observe the fur for flourescence. A Wood's lamp is a special UVA-A light and infected hairs can fluoresce ('light up') under its light. While some ringworm fungal species may not flouresce, a Wood's Lamp can be useful because Microsporum canis will always flouresce and this is the main clinically relevant fluorescing veterinary dermatophyte.³

Flourescence of ringworm fungus under a Wood's Lamp.

Photo credit: @canine_myofascial_therapy

Treatment of Ringworm in Dogs

Although ringworm in most healthy animals will clear up on its own, treatment is recommended due to the contagious nature of the disease and its ability to spread to humans.⁵ A combination of topical and environmental treatment is ideal - and oral medication may be required in certain circumstances.

How To Get Rid of Ringowrm in Dogs

1. Clean the environment

Ringworm can persist in your home environment for months or even a year. Getting rid of it requires extensive sterilisiation and cleaning of your home and all bedding. Environmental decontamination involves cleaning to remove as much hair and debris as possible, and then disinfecting surfaces to kill any remaining spores.

2. Treat your dog's ringworm

To clear up the infection on your dog, ringworm requires topical treatments. Ringworm can be killed by repeatedly soaking the area with iodine-based products such as Troy Iodin Spray or Betadine - however Betadine should be diluted 1:4 with water before applying to your dog's skin. Ringworm should also be treated with an antifungal lotion containing a compound such as miconazole (such as Fungafite) or iodine (like Quit Itch Lotion) as well as 2-3 weeks of daily washing with an antifungal shampoo containing iodine or miconazole such as Malaseb. View more about these products below.

It's important to keep in mind that ringworm may require weeks, or even months, of strict treatment. Never stop treatment before your vet has given you the 'OK'!

3. Additional Skin and Immunity Support

Remember - a healthy immune system and skin barrier will be able to fight off ringworm by itself with time, so whatever you can do to help support your dog's skin is a good idea. This might include supplementing with Omega Fatty Acids (my top recommendation for dogs is Megaderm Nutritional Supplement), introducing a pet probiotic (my top recommendation is Vetafarm Synbiotic Meal Topper), or swapping to a premium quality pet food if you aren't already feeding one.

4. Address Stress and Anxiety

Tying in with extra immune support as outlined above, it's vital to reduce stress for your pup while they recover. The best treatment for anxiety in dogs does vary depending on the situation, but a good place to start is with proper training, consider an anxiety supplement (my top suggestion is Zylkene), and following the steps in my article below:

For more tips on treating stress and anxiety in your canine friend, see my article How To Reduce Anxiety in Dogs.

5. Treat your family if you have lesions

. If you or your family members have lesions, it's best to seek the advice of your doctor - and get a proper diagnosis to ensure they are actually ringworm lesions. The typical treatment for humans is very similar to cats; ie, topical creams and iodine or miconazole-based washes combined with environmental cleaning and good hygeine. As with cats, it can help to support your immune system and skin barrier with good nutrition (particularly Vitamin E, C, D, Omega Fatty Acids, probiotics, and plenty of water!)

Does Advocate treat ringworm in dogs?

No! Advocate does not treat ringworm and is completely ineffective against it. This is because Advocate is an anti-parasite treatment that protects dogs against fleas, intestinal worms, and heartworm - and because ringworm is caused by a fungus (NOT a worm!), Advocate has no effect.

The Best Ringworm Treatments for Dogs Compared

References

1. Frymus T, Gruffydd-Jones T, Pennisi MG, Addie D, Belák S, Boucraut-Baralon C, Egberink H, Hartmann K, Hosie MJ, Lloret A, Lutz H, Marsilio F, Möstl K, Radford AD, Thiry E, Truyen U, Horzinek MC. Dermatophytosis in cats: ABCD guidelines on prevention and management. J Feline Med Surg. 2013 Jul;15(7):598-604. doi: 10.1177/1098612X13489222. PMID: 23813824.

2. Boehm TMSA, Mueller RS. Dermatophytosis in dogs and cats - an update. Tierarztl Prax Ausg K Kleintiere Heimtiere. 2019 Aug;47(4):257-268. English, German. doi: 10.1055/a-0969-1446. Epub 2019 Aug 21. PMID: 31434126.

3. Moriello KA, Coyner K, Paterson S, Mignon B. Diagnosis and treatment of dermatophytosis in dogs and cats: Clinical Consensus Guidelines of the World Association for Veterinary Dermatology. Vet Dermatol, June 2017; 28(3): 266-e68.

4. Barlough J, Timoney J, Hagan W, Bruner D, Scott F, Gillespie J (1988). Hagan and Bruner's Microbiology and Infectious Diseases of Domestic Animals: With Reference to Etiology, Epizootiology, Pathogenesis, Immunity, Diagnosis, and Antimicrobial Susceptibility. United Kingdom: Comstock Pub. Associates.

5. Miller W H, Griffin C E, Campbell K L: Fungal and algal skin diseases. Muller and Kirk’s Small Animal Dermatology, 7th ed. Saunders Elsevier, St. Louis 2013 pp. 479-619.

6. Moriello KA: Decontamination of carpet exposed to Microsporum canis hairs and spores.. J Fel Med Surg 2017 Vol 19 (4) pp. 4.