Ringworm not really a worm but a fungus contagious to pets and humans

Q: My American bulldog Tully has small pink and hairless circles on his belly. His vet says they’re ringworms. I’ve been told it’s very catching and that he needs to stay away from everyone. My friends say I just need to give him deworming medication but all my vet gave me was a shampoo. Is this right?

A: Despite its unappetizing handle, ringworm is not caused by worms. Rather, this common skin infection is caused by a fungus. It’s called “ringworm” as a result of the characteristically circular (“ring”-like) lesions observed on the skin of those who suffer it.

In pets, this often itchy, unsightly infection is most often caused by a fungus called Microsporum canis. These fungi invade the superficial layers of the skin, hair or nails. Because fungi thrive in moist environments, they’re especially persistent in humid climates and damp surroundings (read: South Florida).

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Dr. Patty Khuly has a veterinary practice at Sunset Animal Clinic in South Miami.

The ringworm disease is not only contagious to other animals, it’s considered a zoonotic disease, meaning that it can be transmitted from animals to humans (and vice versa). Children and those with compromised immune systems are most at risk and they should definitely be kept away from Tully until he’s cleared by your veterinarian. They should at least wash their hands and anywhere else where their skin has contacted him — ideally with a disinfectant solution containing chlorhexidine.

In pets, the fungal infection causes the hair to become brittle and break off, leaving hairless patches of skin. These occur most commonly on the face, ears, and legs. Within these hairless patches, the skin may be crusty or pink, especially around the edges (hence, the “ring”-like appearance). But claws can also be affected.

Ringworm is typically spread by contact with an infected animal, but touching objects the infected animal has been in contact with, including bedding and brushes, can also lead to infection (wash these!).

The best way to diagnose ringworm infection in an animal is by fungal culture. If this hasn’t been done, the circular lesions may not be ringworm-related. Allergic lesions, common in American bulldogs, can look like ringworm. That’s why it’s especially important to have him properly tested.

As to treatment: In healthy animals, the infection may be self-limiting, meaning that it’ll eventually resolve by itself. However, pets are usually treated with topical shampoos, dips, oral medications, or all of the above.

But above all, be sure to get the right diagnosis. And never take medical advice from your friends!

Dr. Patty Khuly has a veterinary practice at Sunset Animal Clinic in South Miami. Her website is Send questions to