Ringworm is a skin disease caused by a fungus (plural: fungi). Because the lesions are often circular, ringworm was once thought to be caused by a worm curling up in the tissue. However, ringworm has nothing to do with any type of worm.
Ringworm is also known as dermatophytosis. There are four species of fungi that can cause dermatophytosis in cats; however, it is most often caused by the organism called Microsporum canis. Microsporum canis is so well adapted to cats that up to 20% of cats are thought to be asymptomatic carriers, meaning they have the organism but show no outward signs.
Ringworm is actually an infection in the dead layer of the skin, hair, and nails. The fungus is able to utilize this dead tissue (keratin) in the skin as a source of nutrition.
What cats are likely to get ringworm?
Genetic and environmental influences play an important role in feline ringworm infection. A significant amount of research remains to be done on this disorder. It appears that Persian cats are affected most frequently. In catteries, ringworm can be hard to control because of the numbers of animals involved.
What are the clinical signs?
The fungi live in hair follicles. As the organism invades and weakens the hair shafts, hairs break off at the skin line. Patches of hair loss tend to be round; however, as the fungus multiplies, the lesions may become irregularly shaped and spread over the cat's body. These patches may be associated with scaling and crusting of the skin. The lesions are sometimes pruritic (itchy), but this is not a consistent finding.
The incubation period is 10-14 days. This means that the exposure to the fungus and establishment of infection occurs 10-14 days before any lesions occur.
How is ringworm diagnosed?
Feline ringworm can be diagnosed by four different methods. In some cases, more than one technique is used.
How is it transmitted?
Transmission occurs by direct contact between infected and non-infected individuals. It may be passed from dogs to cats and visa versa. It may also be passed from dogs or cats to people and visa versa. If a child has ringworm, he or she may have acquired it from a pet or from another child at school. Adult humans are relatively resistant to infection unless there is a break in the skin or there is suppression of the immune system (AIDS, chemotherapy, etc). Children are quite susceptible. Consult with your family physician if any family member develops suspicious skin lesions.
Transmission may also occur from the infected environment. The fungal spores may live in bedding or carpet for several months. They may be killed with a dilution of chlorine bleach and water (1 cup of chlorine bleach in a gallon of water) where it is feasible to use it.
How is it treated?
There are several methods for treating ringworm. The specific method(s) chosen for your cat will depend on
the severity of the infection, how many pets are involved, presence of children in the household, and how difficult it will be to disinfect your cat’s environment.
Phone: 978-952-8500
