Ringworm is a common skin disorder otherwise known as tinea that can affect the skin on the body (tinea corporis), the scalp (tinea capitis), the feet (tinea pedis, or athlete's foot), or the groin (tinea cruris, or "jock itch"). Ringworm is not, as its name suggests, caused by a worm. It is caused by a fungal infection of the skin, and the fungi responsible for the infection are known as dermatophytes.
The fungi that cause ringworm tend to grow in warm, moist areas of the body, such as areas of frequent sweating. Most commonly, ringworm results in itchy, scaly, and reddened skin and bald patches if the scalp or beard areas are involved. The infection is highly contagious and is passed from person to person through direct skin contact or via contact with contaminated items such as toilet articles, clothing, and even by contaminated shower or pool surfaces.
Animals can also be affected by ringworm and may transmit the condition to humans. In this case, ringworm is an example of a zoonotic disease, or a disease transmitted from animals to humans. Although cats are affected by ringworm more than dogs, dogs are also commonly affected. In animals, ringworm causes raised, circular areas that frequently are crusted over and associated with hair loss. However, some infected cats may also carry the fungus without showing any symptoms. On the other hand, infected dogs almost always show the typical skin symptoms of ringworm.
Studies have shown that up to 13% of human ringworm infections (tinea capitis) are caused by an organism that commonly causes ringworm in cats. Other studies have shown that in 30%-70% of households in which a cat develops ringworm, at least one person will develop the condition. Young children, the elderly, and people whose immune function is compromised for any reason are most susceptible to the infection.
Other animals that can develop ringworm (and can transmit the infection to humans) include dogs, cows, goats, pigs, guinea pigs, and horses. As with transmission among humans, direct contact or contact with objects the infected animal has touched (such as bedding, grooming articles, saddles, furniture, carpeting, etc.) is responsible for spreading the infection.
Ringworm is a treatable condition in both animals and humans. Topical (applied to the affected area) medication is the usual treatment for ringworm. In severe or resistant (not responding well to topical medications) infections, oral antifungal medications (taken by mouth) may be prescribed. If a pet has been infected with ringworm, it is important to thoroughly disinfect the home to rid the environment of any remaining fungal spores after treatment.
United States. Centers for Disease Control and Prevention. "Ringworm and Animals." July 28, 2010. <http://www.cdc.gov/healthypets/diseases/ringworm.htm>.