By Dr. I Elizabeth Borgmann. No, ringworm is not a worm! It’s a fungus! Ok, now that we have that out of the way let’s get on with our discussion.
In my first article I gave an overview of what you might expect as you and your vet plod your way along in determining what skin problem your pet has. Then I provided you with more insight into parasites and bacterial and yeast infections. Now let’s look at one more infectious little culprit: fungi.

To be clear, yeast is a single celled fungus. I technically should be talking about it here but instead I lumped it into our previous discussion of bacterial infections. This time I’ll be talking about two common fungal genera: Microsporum and Trichophyton. Think mould. Think hyphae. (See, you shouldn’t have skipped out of grade 12 biology class!)

Just the words Microsporum and Trichophyton might turn you off but unfortunately ringworm genera and species don’t have cute names (though I would argue that everything sounds better in Latin – in the same way that basic restaurant pasta dishes written in Italian always taste better).

Let’s take a step back to basic grade 12 biology class and look at how fungi grow. I’m going to use the common fairy ring in the garden as an example since most of us have seen those. Start with a spore (think of this as a seed) and let this grow. As this germinates, it spreads out in a circle. The hyphae (think of these as fingers, branching or webbing) reach outward from the centre. At the end of hyphae you will get fruiting bodies where more spores are produced (the mushrooms of the fairy ring). By now, you probably get the idea where the descriptor ‘ring’ in ringworm comes from.

Ringworm in pets results in a round lesion that spreads outward with hair loss in the middle and crusts and papules on the outer circle. It is most common on the face (from rooting around in the ground or by chasing and eating rats). The next most common areas to be affected are the feet/legs.
Ringworm lives on keratin, (the material skin, hair shafts and nail beds are made of).

There is another form of ringworm, kerion, which your pet may get. This is where the hyphae grow downward into the skin resulting in a thick nasty looking crust. This occurs most commonly on the nose.

Here is the tricky part. Ringworm can look just like a bacterial infection. And ringworm lesions occasionally get secondary bacterial infections.
How will your vet know if your pet has ringworm? Sometimes, it is obvious. Other times skin scrapings and impressions may help. The hyphae can sometimes be seen with special treatment. The use of a wood’s lamp may confirm your vet’s suspicion of ringworm. Or your vet may need to do a culture. (Remember in the first article that we talked about the importance of history? If you have a skin lesion that turned up just before or after your pet’s problems developed, you need to let your vet know!)

Where does ringworm come from? Ringworm is everywhere! And it spreads across species. Being a fungus it can be found in the ground (commonly on farm land); on other species of animals and on items those species come in contact with. The Fraser Valley’s damp moderate climate is great for growing fungus.

Naive and young animals are the most likely to pick up ringworm. Young children in kindergarten often pick up ringworm from each other and they can bring it home to your strictly indoor cat.

Athlete’s foot and jock itch is a form of ringworm and can be spread to your pets (so watch those gym showers).

Other pets and farm animals can be a source of infection (horses, cows, pigs). Pests, such as rodents, can harbour ringworm as well.

As much as your 5 year old child can pass ringworm onto your pet, your pet can pass ringworm onto your children. About 30% of the cases of ringworm in people can be traced to pets.

So how do you treat it? It depends.

Ringworm is self limiting and within 1-3 months it goes away on its own. Deciding to treat depends on the severity and who else may contract the infection.

Small localized lesions can be treated with creams, though this is rarely done. (Pets do tend to lick the creams off.) It is more common to treat both localized and generalized lesions with ‘dips’. Dips mean the pet is saturated with an anti-fungal solution (most commonly enilconazole or lime sulphur). These need to be repeated several times. Other bathing solutions may be employed such as chlorhexidine/miconazole combination shampoos.

There is some debate as to whether you should shave your pet to treat them. One side argues that it reduces the spread by eliminating the hair in which the fungus grows. The other side argues that it will drive the infection deeper through the micro-trauma caused by clippers. If they are shaved, it should be done with a longer blade (not a surgical clip).

Depending on the severity and depth of the ringworm, and any other underlying issues (within the pet or the household) your vet may choose to prescribe itraconazole. It’s a great drug but it’s expensive.

Environmental control is key. The spores sit in the crusts and hair. Frequent vacuuming picks up the spores and crusts. Treat the vacuum bag carefully when disposing of it! In Canada and Europe, enilconazole foggers are marketed for poultry facilities and can be used in houses. Sodium hypochlorite (household bleach) will work as well but it will pit and rust metals and may be carcinogenic.

Just be aware, you can do everything right, and still pick up ringworm! And be glad you don’t live in a tropical rain forest! Next time, we’ll start talking about allergies. About 20% of pets in the Fraser Valley suffer to some degree with allergies.

Dr. I Elizabeth Borgmann

Dr. Borgmann has been practicing in the Fraser Valley for over 11 years and can be reached at the Whatcom Road Veterinary Clinic