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Ringworm Around Rosie: How Shelters Can Successfully Prevent or Manage Fungal Outbreaks

Kim Campbell Thornton

Nobody loves it when a pet gets dermatophytosis, popularly known as ringworm, but an individual case is manageable. When ringworm invades an animal shelter, though, the outbreak can be costly not only in terms of diagnosis and treatment—thousands of dollars, according to information from the UC Davis Koret Shelter Medicine Program—but also in loss of community standing. Nobody wants to adopt from a shelter if the animal might have ringworm that could spread to family members. And because outbreaks can be so difficult and expensive to manage, animals with ringworm may simply be euthanized.

That’s why in 2012 Laura Mullen developed San Francisco SPCA’s SPORE program—Shelters Preventing Outbreaks of Ringworm through Education. She spoke at the 2019 Feline Science Symposium last October on how shelters can avoid outbreaks of the zoonotic fungal infection.

“Ringworm’s always going to come into the shelter but having the right tools and education can help to avoid outbreak situations,” she says. The key is having the right tools, a consistent plan, and a response team of volunteers who know what to do when ringworm is found in the shelter.

Get a History

As much as possible, find out where the animal came from. Did all the kittens come from the same yard or is one from a different area? What type of situation did they come from?

Cats from hoarding situations are more prone to ringworm and might warrant a closer look. Most important, though, is a thorough physical exam for every animal. A good screening system helps ensure that ringworm doesn’t run rampant in the shelter.

Light It Up

Part of that screening system is use of a Wood’s lamp. A Wood’s lamp exam from nose to tail is required for all animals younger than six months coming into the shelter. Most commonly, ringworm lesions are found on face and ears, but Mullen says they’ve found them in all kinds of spots, including beneath the tail and between the toes. Look inside the ears. Clues include hair loss and breaks in hair.

The ultraviolet light of a true Wood’s lamp, which unlike a generic UV lamp fluoresces at a specific wavelength of 360 nanometers (nm), causes some strains of Microsporum canis—the most common feline ringworm species—to fluoresce a bright apple-green. Don’t mistake the yellow glow of sebum or the white or blue of medications or bacteria for ringworm. With practice, recognizing ringworm fluorescence becomes second nature. Other ways to distinguish M. canis fluorescence from unrelated causes:

*Ringworm can’t be brushed off easily

*Only hair shafts fluoresce apple-green rather than a larger area of skin

Dermatophytosis develops when spores—most often Microsporum canis—are released from a lesion and land on hair. Over a period of seven to 10 days, they burrow through the outer keratin layer to the inside of the hair shaft, where infection occurs. That time period between exposure and infection is crucial for prevention.

“You can take a sporicidal shampoo and wash that animal, kill spores on contact, and kill the seeds of the infection before it starts,” Mullen says.

Not using a Wood’s lamp can lead to missed cases. Sometimes animals have a bald or crusty spot when they come in, but before hair loss develops, kittens (who are greater risk than canines) or puppies may look normal on a visual exam. Infection goes unnoticed until crusty lesions develop.

“By then kitten has made friends with other cats and been socialized with people who are now exposed to it. We would eventually see it because of all the hurdles they have to jump through—spay/neuter, going to the adoption center, going to a new home—but by then they’ve traveled through the shelter, they’ve made lots of friends, they may even make it to a home, and we want to try to avoid that situation.” Using a Wood’s lamp on entry is the way to do that.

Other Tools and Techniques

A toothbrush is another simple but effective tool. When physical and Wood’s lamp exams don’t show glowing lesions, glowing hairs, or hair loss, gathering samples with a toothbrush is a simple, non-invasive technique that can be carried out by volunteers and is kinder than plucking hairs. These animals may have spores on the haircoat but no infection yet. The samples can then be cultured.

Mullen teaches a standardized way of gathering the samples using the Mackenzie brush technique. With a new toothbrush just removed from packaging, kittens receive 15 brushstrokes over the entire body. The last five strokes go over the lesion itself, ensuring that spores don’t get spread elsewhere on the body.

“The kittens love the toothbrushes, and it’s an easy, non-invasive way for volunteers to help,” Mullen says. “If I teach a standardized process, I don’t have to be the one to do it.”

Gathering and inoculating all cultures the same way ensures standardized results. And just because a culture grows doesn’t mean animals have a significant amount of infection. They may just be exposed. A culture with only four colonies indicates exposure. “A true infection, what we call a P3, has about 300 colonies,” Mullen says. If the P score is slightly high, culture again. Some cases may stay in isolation for two weeks, but that’s better than keeping all the kittens in isolation for eight weeks, slowing their movement through the system, Mullen says. Animals stay in isolation until they have two consecutive negative cultures.

Those animals who are just exposed can be bathed with a sporicidal shampoo or lime-sulfur dip and released to the adoption floor. Kittens with infections are treated and loved until they “graduate” from the ringworm treatment program to the adoption floor.

“Our ringworm kittens get adopted much more quickly because they are super socialized by our volunteers and medical volunteers,” Mullen says. “They’re used to a lot of handling. They’re very confident cats. We will get cats that are shy, and in a week or two they come around. We get very little aggressive behavior from them.”

Volunteer Hit Team

Often, shelters may not have the time, space, resources, or staff to treat animals with ringworm. That’s where volunteers come into play. They can be trained to recognize ringworm and carry out the prevention and treatment program. The SPORE program is approximately 70- to 80-percent volunteer-driven.

“You just have to ask them,” Mullen says. “They will do so many things I never thought a volunteer would want to do.”

Volunteers also come up with great ideas. It was a volunteer, Mullen says, who came up with the idea of cutting sponges into tiny squares to make it easier to treat kitten faces and ears.


Oral, topical, and environmental therapies take place concurrently to get ringworm under control. The treatment ward is scrubbed down weekly, with regular spot cleaning and laundering of bedding. Weekly cultures determine how animals are responding to treatment. An identification chart is available showing how the different species look on the culture plate and on microscopic exam. While all the species look different, they are all treated the same. M. canis is the hardiest species, and it’s what is typically seen in shelters.

Animals are medicated with mitroconazole and receive a lime-sulfur dip. The topical treatment is applied using a pressurized mist sprayer and warm water, followed by a massage afterward. Shelter volunteers or staff with Fear Free training may also use techniques such as considerate approach and gentle control, as well as monitoring FAS levels.

Volunteers and kittens enjoy the experience.

“They’re very used to this and they have all sorts of people handling them,” Mullen says. “They’re four or five weeks old, they don’t know any different, and they love it. Because they’re raised with this, they’re easy to do and it’s easy to have volunteers do it.”

With the animal on a towel, they’re sprayed from the neck down. Every area needs to be treated because contact is what kills the spores, but animals don’t have to be sopping wet. They get a quick squeeze dry and then go under a heat lamp so they’re not sitting around cold or wet. They might turn yellow from the sulfur dip but the color goes away after a couple of days.

“They’re stinky but it smells like victory, it smells like lives being saved,” Mullen says. “That changes the conversation in the shelter. We’re owning that smell and we’re saving cats.”

This article was reviewed/edited by board-certified veterinary behaviorist Dr. Kenneth Martin and/or veterinary technician specialist in behavior Debbie Martin, LVT.

Kim Campbell Thornton is content manager for Fear Free Pets and is a Level 3 Fear Free Certified Professional. She has been writing about dogs, cats, wildlife, and marine life since 1985 and is a recipient of multiple awards from the Cat Writers Association, Dog Writers Association of America, and American Society of Journalists and Authors. When she’s not writing or editing, she’s competing in nose work trials with Harper and Keeper, her Cavalier King Charles Spaniels.

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