Ringworm is a common skin infection in cats that is sometimes seen in dogs - and also on people. What is the best approach for treating this stubborn fungus?
Ringworm is not a worm at all; it is actually a very common fungal skin infection among cats and some dogs that can also be spread to humans. There are three species of fungi that cause disease in dogs and cats: Microsporum gypseum, Trichophyton mentagrophytes, and Microsporum canis. Microsporum canis is the most commonly seen and can produce lesions on humans.
How Did My Cat Get Ringworm: Fungal spores can be found in the environment where other infected cats have been. Infected cats that have previously visited groomers, boarding facilities, or just been in their own home will have left spores behind. These spores can live in the environment for up to 18 months. Fungal spores can also be found outdoors, in the dirt. When an animal comes in direct contact with the spores they can develop ringworm lesions. Some cats can be carriers and actually shed the spores without ever developing lesions.
Symptoms of Ringworm: Signs or symptoms of ringworm include a rapidly growing circular patch of dry skin, some areas will be red, crusty, and raised. The hair in the lesions will appear to have been broken and lesions usually appear on the face, ears, and head. Lesions may or may not be itchy. In severe cases the lesions will spread to the rest of the body. Young cats are most susceptible as are cats with a poor immune system. Lesions may also appear on owners.
Diagnosing Ringworm: Your veterinarian might diagnose ringworm in a couple of different ways.
- Wood's Lamp - A Wood's lamp is a special black light that when shined over lesions infected hair shafts are revealed by fluorescing. This method will not detect all fungal infections; in fact only about 50% of the M. canis organisms will fluoresce.
- Examine Hairs Under The Microscope - The veterinarian can collect some of the hairs and scales and look under the microscope for fungal elements.
- Culture - A culture is the most accurate method for diagnosing fungal infections. Fungal growth is slow and can take about 14 days before results are seen. Many veterinarians will start treatment before obtaining results; this is to provide relief to you and your pet.
Treating Ringworm: Treatment is usually done through both topical creams and shampoos and oral anti-fungal medications. Treatment will vary depending on the severity of the case. In some cases the entire coat may need to be clipped in order to remove contaminated hairs (the clippers will then be contaminated and need to be washed in a dilute bleach solution).
- Topical Creams: Localized lesions can be treated with topical anti-fungal creams. Treatment should be continued for 2 weeks after the lesion has cleared. Some common medications include but are not limited too: Conofite, Miconazole, and Lotrimin.
- Shampoos: Generalized lesions will need the entire body treated; this is easily done with shampoos. Baths are usually done 1 - 2 times weekly until cultures are negative. This may take 4 weeks or more. Common shampoos include but are not limited too: Lyme Dip, Nolvasan, Betadine, and Melaseb.
- Oral Medications: Oral medications are generally used along with a shampoo. The shampoo will work to remove spores from your pet so that they are not shed in the environment. The most common oral medications are Griseofulvin and Ketoconazole. These medications need to be monitored closely by your veterinarian; they can be toxic if dosage instructions are not followed.
Additional Information:
- Ringworm is contagious. Handle animals as little as possible and wear disposable gloves.
- Your home should be cleaned to remove spores and prevent reinfection. Vacuum weekly and dispose of the bag each time. Clean hard surfaces with a 1:10 bleach solution. Surfaces that are not easily cleaned should be repainted. Throw toys and bedding away that cannot be washed.
- See your doctor if lesions develop on you or family members.
References:
Common Diseases of Companion Animals, Alleice Summers, MS, DVM (Mosby, Inc. 2002)
Pawprints and Purrs, INC, Ringworm In Cats
PetEducation.com, Veterinary & Aquatic Services Department, Drs. Foster & Smith, Inc., Ringworm
