Can Dogs Get Ringworm?

If you are a parent, you are likely familiar with the horrible-sounding skin condition known as ringworm.

Children are especially susceptible to it, and, I’m sorry to say, your dog can suffer from the condition too. Fortunately, ringworm is a relatively minor and treatable medical condition (for both kids and dogs).

Want even better news? Ringworm has nothing to do with worms at all, so you can stop hyperventilating at the thought of some critter crawling under your pet’s skin.

What Causes Ringworm?

Ringworm infections are caused by tiny fungal organisms called dermatophytes (in fact, your vet may use the term dermatophytosis instead of ringworm). These organisms feed on keratin — a protein that helps make your dog’s skin, hair and claws waterproof.  

The world is home to scads of dermatophytes. Some are very species-specific organisms that primarily colonize a given animal, whereas others are flexible and capable of surviving on a variety of different species. Some are even capable of colonizing humans.

Nevertheless, dogs primarily suffer infection from one of three primary species:

• Microsporum canis – According to the Merck Veterinary Manual, this pathogen is responsible for approximately 70% of U.S. cases. This particular fungus is also responsible for most cases of ringworm in cats.  
• Microsporum gypseum – A soil-dwelling fungi that is most likely to occur in dogs (and other animals), who root and dig in the dirt. It is most commonly identified in South American cases of ringworm.
• Trichophyton mentagrophytes – The least common fungal species responsible for ringworm infections in American dogs, Trichophyton mentagrophytes is actually the most common dermatophyte in other parts of the world, but very uncommon in North America..

How Do Dogs Contract Ringworm?

Dermatophytes primarily spread through direct or indirect contact.

Your dog may, for example, rub up against another dog at the park who has a ringworm infection; or she may contract ringworm by touching an object that has been in contact with an infected animal.  

Unfortunately, you can contract ringworm from your dog in exactly the same way.

In fact, it is possible for the fungus to spread to all the members of your family and cause you to spend a large chunk of time in the doctor’s office. This further illustrates the need to address ringworm promptly and aggressively.

Be aware that some dogs may harbor dermatophytes without developing any symptoms. But while they don’t personally suffer from these fungi, these “silent carriers” can still spread ringworm to the other members of your family.

What Are the Signs and Symptoms of Ringworm?

Most commonly, ringworm presents in dogs as one or more vaguely circular, hairless lesions. These hairless areas may also feature a crusty, scabby red center, numerous pustules, and broken hair shafts.  

However, ringworm infections can have an atypical appearance, so you must visit your veterinarian to obtain a positive identification. Very young puppies, geriatric dogs and those with a compromised immune system may suffer from generalized ringworm, in which large portions of the body become infected.

How Will Your Veterinarian Confirm the Diagnosis?

Even if your dog has a text-book ringworm lesion, your veterinarian will probably want to confirm the diagnoses via other lines of evidence.

Your vet will want to be certain that dermatophytosis is the problem, and not, for example, folliculitis (an inflammation of the hair follicles, typically bacterial in nature) or mange.

Generally, one or more of the following methods are used:

• Your veterinarian may shine a special light called a Wood’s lamp on the hairs surrounding your dog’s lesion. This light will cause about 50% of M. canis colonies to emit a yellow-green glow. However, while this is a relatively quick and non-invasive procedure, it does not indicate all M. canis infections and is completely ineffective for diagnosing M. gypseum or T. mentagrophytes infections.
• Your veterinarian may pluck hairs or skin flakes from the lesion’s border and view them under a microscope. Although this may reveal the presence of any of the three primary fungi responsible for ringworm infections, it is not foolproof. Many times, veterinarians may simply not see the fungi on the slide.   
• Your veterinarian may collect hairs or skin cells from the border of the lesion and send them to a laboratory to be cultured. The laboratory will perform the culture by placing the sample in a vial with a food source and then waiting for the colony to grow large enough to be identified. Fungal cultures can take a few weeks to grow, so your vet may simply begin treatment while waiting for the results. 

This video shows how veterinarian Dr. James Talbott works to identify ringworm in a dog.

What’s the Prognosis With Ringworm in Dogs?

This is a good-news-bad-news situation. While ringworm is treatable, it is not an easy foe to vanquish.

Infections often persist for as long as three weeks, even when aggressive treatment is employed. During this time, your pet may continue to spread the fungus throughout your home, which can lead to infections in the human members of your family.

However, there is a silver lining: Dogs often develop a short-lived immunity after battling the fungus for a while. This helps them to fight off the initial infection and prevent it from spreading. It is still important to secure veterinary assistance, in the interest of making your pup feel better and reducing the chances that the fungus will spread to the other members of your family (be they two-legged or four).

How Do You Treat Ringworm?

In short, ringworm is treated through a combination of medications and the use of strict hygiene practices. The medications will kill the fungi living on your beloved buddy and a series of thorough cleanings will help eliminate the fungi from the environment.

Typically, vets will use a combination of of oral capsules or tablets and a medicinal, anti-fungal wash. These washes will often need to be applied every three to four days. You’ll need to do so outside, and you’ll need to wear gloves while using the topical wash on your pooch.

Note that anti-fungal drugs are very dangerous for pregnant animals, so be sure to notify your vet if there is any chance your dog has tiny pups in her belly.

Veterinarians often trim the hair surrounding the lesions as a matter of practice.

This helps to keep the area clean, reduce the number of dermatophytes in the area and make it easier to apply the necessary medicines.

Unfortunately for your pup’s pride, the vet may recommend that she wear an e-collar while undergoing treatment. This will help keep the area dry and prevent her from ingesting some of the medication.

While your dog is undergoing treatment, you’ll need to perform several deep cleanings of the environment to help expedite the healing process.

Be sure to scrub the floors and walls that your dog contacts with a dilute bleach solution, and wash all of her personal items, including blankets, pillows, dishes, and toys.

It is wise to keep your pet quarantined to the extent it is possible while undergoing treatment to help prevent the fungus’ spread.

How Do You Prevent Ringworm Infections in the First Place?

As with many other medical problems, it is better to prevent ringworm than to treat it after an infection develops. To do so, try to employ the following measures:

• Limit the amount of time your dog spends in damp, warm locations where fungi thrive.
• Do not allow your dog to interact with dogs that exhibit skin problems – this includes other dogs in your family.  
• Inspect your dog regularly to help catch ringworm (or any other skin conditions) quickly and begin treatment as early as possible.
• Bathe your dog with a dog-friendly soap and lukewarm water anytime she has traveled through areas likely to harbor dermatophytes. Just be sure that you don’t bathe your dog too frequently — you can rinse her off with water as often as necessary, but avoid using shampoos more frequently than once every three weeks or so.
• Wash and dry all of your dog’s bedding materials frequently with hot water to help eliminate any spores or fungi present from persisting.
• Unfortunately, some breeds – most notably Yorkshire terriers – appear to be especially susceptible to ringworm. If your breed exhibits such a tendency, take extra precautions to avoid exposing your pooch to problematic fungi.

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As you can see, ringworm is a legitimate concern for dog owners, but it isn’t anything to lose sleep about. Do your best to avoid the problem, and solicit your veterinarian’s help at the first signs of the condition.

But what about you and your dog? Have you ever had to help her beat a ringworm infection? We’d love to hear your experiences (or questions) in the comments section below.