How do cats become infected with M canis?
Ringworm is contagious. Spores are the infectious stage of dermatophytes and are produced by M canis during an infection. They are typically found in clusters around infected hairs and can only be seen using a microscope. Infected hairs are shed into the cat's environment. Cats may become infected either by direct contact with an infected animal or by exposure to a contaminated environment or object such as grooming tools, clippers or bedding. Spores in the environment are very robust and without treatment can remain infectious for up to two years. Spores attach to the skin and germinate to produce hyphae that invade skin and hair. It is not known how many spores are needed to start an infection. Self-grooming, particularly licking, may be an effective way of harmlessly removing spores from the skin and haircoat. Intact skin is very resistant to infection. Mites and lice are generally uncommon. The point being made here is that some degree of self trauma is probably required to enable fungal infection to develop and that ectoparasite infestation may be an additional predisposing factor.