Ringworm is a common fungal skin infection affecting many cats and can be easily transmitted to their human owners.  Ringworm is not a worm as the name suggests but is caused by fungi called Micosporum canis. The presence of ringworm on your cat is usually characterised by a circular patch of broken hair and a dry scaly skin. Ringworm is commonly found on the head and feet and can also affect the claws of a cat where the claws become abraded and uneven.