What is it?
Ringworm is not actually caused by a worm. It is a fungal skin disease (also known as dermatophytosis). Fungi typically live in the soil, but they are able to cause skin disease under the right conditions. Skin disease in pet or house rabbits is usually caused by Microsporum fungi. Skin disease in outdoor rabbits is more commonly caused by Trichophyton fungi.
The disease is named ringworm due to the appearance of infected skin.
Why is it important?
Ringworm is a human health risk. Both types of fungi which cause disease in rabbits cause circular crusty skin patches in humans which may be itchy and spread rapidly. Children, the elderly, and adults who are ill for other reasons, are most at risk of infection.
Fungi produce spores which can survive in the environment for a long time (months to years).
What is the risk?
Ringworm spreads easily by direct contact with hairs or skin flakes from an infected animal. Overcrowding and poor nutrition increases the risk of infection. Ringworm may spread through grooming tools and clippers.
The infection can spread from cats and dogs to rabbits and humans.
What happens to the rabbit?
After contact with an infected animal, skin disease takes 1-2 weeks to develop. The fungus infects growing hairs and surface layers of the skin. Once the growth of the fungus is complete, it produces spores which infect other animals and the environment.
Infected rabbits (and other animals) have patches of hair loss and crusty, scaly skin, especially on the face, eyes, nose and limbs. There may be patchy hair loss all over. Ulcers may develop where skin is damaged. Affected rabbits may or may not be itchy. It is possible for a rabbit to carry infectious fungi without showing signs of disease.
Ringworm is common in young rabbits where they pick up infection from their mothers. Rabbits who are stressed or ill for other reasons are susceptible to infection.
Rabbits may be able to clear the infection themselves, but the infection will persist if the animal is ill for other reasons. It is advised to treat infected rabbits because of welfare implications, and the risk of human infection.
How do you know what is going on?
Both the owner and the rabbit may be affected by ringworm. It is usually suspected by the appearance of skin lesions. Your vet will ask questions on how your rabbit is housed and fed, and whether there are other rabbits in the environment.
Gloves should be worn when handling a suspected ringworm case.
Diagnosis is usually done by looking at a hair sample or skin scrape under the microscope. There is a test called a Woods lamp, which is shone on the affected skin and observed for fluorescence, but not all types of fungus will show up with this method. Fungal culture from a hair sample is the best way to diagnose ringworm. It is very important to distinguish between ringworm and other causes of crusty skin such as Cheyletiella / Fur mites.