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Understanding Dog Ringworm and How to Treat It

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Do some quick online research and you'll learn about all sorts of parasitic worms that can harm your dog. Heartworms, hookworms, roundworms, whipworms, tapeworms ... the list goes on. But one “worm" you may discover is not a worm at all: ringworm.

The term "ringworm" describes two things. First, it refers to a collection of pathogenic fungi, known in the scientific community as dermatophytes. Second, it refers to the condition that those fungi cause (technically known as dermatophytosis). To put it simply, ringworm is a fungal infection of the skin caused by a few types of harmful fungi. 

Cases of dog ringworm are relatively common, and the fungi don't discriminate. Ringworm can infect almost all species of animals and humans. That's one reason why a dog ringworm infection is a serious matter — while it's not life-threatening, it can be spread to other pets or even humans in the home. 

Let's take a closer look at the cause of ringworm, the symptoms it creates, and how to treat your pet so everyone in your family stays safe. 

What Causes Ringworm? 

Dog ringworm: a happy miniature poodle

There are three members of the dermatophyte family that cause dog ringworm: Microsporum canis (the most common culprit), Microsporum gypseum, and Trichophyton mentagrophytes

When these fungi infect a human, they cause a round, raised, red "ring" shape on the skin, which is where ringworm gets its name. However, the red ring may not be as apparent in our canine friends. 

The fungus feeds on the outermost layer of your dog's skin and the hair follicles, and sometimes on the nails. The infection remains superficial — it stays on the skin and will not invade your dog's body, but it can cause further health problems if it's not dealt with in a timely manner. 

What Are the Symptoms of Ringworm? 

While a human ringworm infection is easy to spot thanks to the raised red ring shape that the fungus causes, such an obvious marker might not appear in your canine companion.

In dogs, the first sign of ringworm is usually one or more circular areas of hair loss. As these circles get bigger, the skin in the center often starts to heal and grow hair again, creating the appearance of patches of hair loss. 

The hair around these skin lesions will usually be quite dry and brittle, breaking off of your dog's body easily and increasing the likelihood that ringworm is spread to other pets or humans as they come in contact with that hair.

The major symptoms of ringworm in dogs include:

  • Hair loss (alopecia), particularly in circular ring shapes
  • Dry and brittle hair
  • Inflamed skin 
  • Scabs or crusting on the skin
  • Brittle or broken claws (if the ringworm fungus has infected the claws)

Note that ringworm usually does not cause itchiness, so you probably won't see your dog scratching at his or her ringworm lesions. This can help to differentiate ringworm from other skin conditions that cause hair loss, such as mange or allergies

Are Other Pets and Humans at Risk? 

Yes, a ringworm fungus can easily transmit to other pets in the home, including cats and small mammals. It can also be contracted by humans. 

The shedding or breaking of infected hairs is the main method through which ringworm spreads. In fact, that's how dogs tend to get the fungus in the first place — they come into direct contact with another infected dog, or that dog's bedding, bowl, furniture, comb, or other object. 

To make matters worse, objects and surfaces can remain contaminated with the fungal spores for a long time — up to 20 months

It's also worth noting that some dogs can have a ringworm fungus living on their skin and in the hair follicles without showing any symptoms. These dogs, called asymptomatic carriers, can spread ringworm to other animals or humans without showing any signs of the infection whatsoever. 

Fortunately, most healthy adult humans are resistant to the fungus. It's more likely to affect individuals with compromised immune systems, elderly people, or young children. That said, it's possible for any healthy adult to contract ringworm, especially if there’s a break in the skin, like a scratch or small wound. 

How Is Dog Ringworm Treated? 

Dog ringworm: a large dog stands with his front legs up on a picnic table

A veterinarian will diagnose a case of dog ringworm with a physical examination to look for clinical signs, as well as a series of tests including a fungal culture of skin or hair cells. 

Your vet may also examine your dog's hairs under a special ultraviolet light called a Wood's lamp. This tool can help the doctor detect bacterial or fungal infections, although it isn't always conclusive. 

Treating Your Dog

Most cases of ringworm are handled using a combination of topical treatments and systemic therapy. Topical treatments involve things like medicated shampoos, which you'll use to bathe your dog regularly, as well as creams and ointments that are applied to affected areas. 

Systemic therapy means, in this case, giving your dog an oral medication with antifungal properties. Griseofulvin is often used, although newer medications like itraconazole or terbinafine are seeing increased use among veterinarians thanks to their lower risk of side effects.

Ringworm treatment usually lasts for at least six weeks, with cultures being taken periodically to find out if your pet is still infected with the fungus. Treatment must not be stopped too soon or reinfection can occur. 

Treating Your Environment

Since ringworm is contagious to other pets and humans, taking steps to decontaminate your home environment is essential to stop the spread of infection. Your vet will probably recommend steps like:

  • Keeping your dog quarantined in a specific area of the house that is easy to keep clean
  • Restricting other pets or human family members from coming into contact with your pup
  • Vacuuming floors and carpets regularly
  • Cleaning potentially contaminated objects or surfaces with a diluted bleach solution 

When you handle your dog directly, perhaps to take him or her to the vet's office for another fungal culture, make sure to wear gloves. Wash your hands thoroughly after your dog is back in their designated containment area. 

When steps like these are taken and proper treatment is given for a long enough time period, the vast majority of dogs will recover fully from a ringworm infection. The biggest danger isn't necessarily to the health of your pooch, it's the potential for the fungal infection to spread to other family members or pets in the home. 

Can You Prevent Dog Ringworm?

There isn't a specific preventative measure against ringworm, like a vaccine, so it's not always possible for you to prevent ringworm in your dog. If your pup comes into contact with another animal that has the infection, they're likely to contract it themselves. 

However, you can minimize the likelihood that your dog will get ringworm by keeping your home clean at all times and preventing your dog from going near other infected animals whenever possible. 

It’s also a good idea to boost your dog's immunity, which is their first line of defense against disease and infection. Try natural, immune-boosting supplements in tandem with a healthy diet. You might also consider beneficial supplements for skin and coat health. 

Generally speaking, ringworm prevention isn't something you have to spend a lot of time focusing on unless your dog or other pets already had it. In that case, you'll want to make sure that the infection is completely cleared up before lifting your pet’s quarantine. You’ll also want to decontaminate your home and your pet's items thoroughly to ensure the fungal spores don't spread. 

To learn more about how to improve your dog’s overall health, visit the PetHonesty blog for the latest information.