FEBRUARY 8, 2012
It may be surprising for some to learn that the skin infection known as ringworm, or dermatophytosis, is not actually a worm or parasite at all, but a fungus. The lesion will not always be in the shape of a ring, but it will appear scaly in the center with a red irritated color on the periphery.
“Household pets generally pick up the disease from other animals. Where the infection occurs on the skin there will be a bald patch, but sometimes they may just have a few broken hairs,” says Dr. Leon Russell, professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences.
Ringworm is highly contagious and can pass from person to person either through direct contact, through contact with an infected object, contact with an infected pet or infected soil. Humans can contract ringworm from animals very easily by touching the infected area directly or through contact with objects which have been exposed contaminated with the fungus or its spores.
Animal ringworm types, usually from a dog, cat, or rodent are more likely to be transmitted to young children. With children it is often found in the scalp region.
“Fungi that mostly live in human skin are called ‘anthropophilic’, those that live on animals are called ‘zoophilic’, and those that prefer to live in soil are called ‘geophilic’ fungi,” explains Russell.
The anthropophilic ringworm is mostly seen in developing countries such as Africa, or parts of Asia by human to human transmission. Many times this occurs from sharing hairbrushes or combs, and unless someone’s immune system is highly compromised then the disease is not life threatening.
“Tinea pedis, or athlete's foot, is the most common form of ringworm found in humans and the most difficult to treat. The rash most often appears in the moist areas between the toes, though the rest of the foot can be infected as well. Itching and burning are typical symptoms,” says Russell.
Community swimming pools, used towels, health clubs, steam rooms and showers are common areas where athlete's foot can be contracted.
“Rarely humans can transmit the disease to animals. An example of this might be if a person with athletes foot comes home, takes their shoes off, and scratches or rubs ol’ Fido with their bare foot,” says Russell.
Livestock such as cattle or horses are more likely to have ringworm when they are kept inside their stalls in the winter because of the rubbing up against wood and other stall materials.
“These cases are seen more in the Northern parts of the United States where the weather is colder. Generally, when the weather becomes warmer again and the animals are turned outside into the sunshine of pastures, the disease begins to clear up,” says Russell.
In horses ringworm is seen usually in places where rubbing may occur, such as where a saddle or bridle might touch. Adults are more likely to contract ringworm from a horse rather than children, due to occupational exposure and handling.
The effects of ringworm tend to be superficial ones of appearance, though, if not treated in animals it can easily spread and cause scar tissue.
Some people, mostly children, who contract ringworm from a pet can sometimes have a reaction with their skin tissue resulting in bulgy lesion-looking patches on the skin called Kerions. These are more severe in appearance compared to the normal reaction and can be very upsetting for the person.
“The treatment for ringworm in humans or animals is usually going to involve a topical medication. Oral medication may be needed if the ringworm is chronic, and therefore can sometimes take up to three or four months to clear. It is certainly not a reason to get rid of a dog or cat because it can be treated,” says Russell.
“The most common fungal species that may cause ringworm in dogs and cats are Microsporum canis. If you suspect that your pet has ringworm, a veterinarian will be able to determine if that is the case or not by examining the animal under special lighting wherein the fungus glows,” explains Russell.
If a pet is diagnosed with ringworm it is best to take steps to disinfect objects that the animal has been in contact with, using chemicals like chlorine diluted in water.
It is important to bring your pet, especially young pets, in for their vaccinations and checkups to ensure that diseases such as ringworm are not causing any problems.
Pet Talk is a service of the College of Veterinary Medicine & Biomedical Sciences, Texas A&M University. Stories can be viewed on the Web at http://vetmed.tamu.edu/pet-talk.