The skin lesions usually start as small raised spots from which the hair is lost. The bald patches then become scurfy or a thick dry crumbly scab may form. However, ringworm can present in many different ways so often our vets will recommend testing to rule the condition in or out.
In many cases there may only be a couple of lesions but if left untreated and especially if spread by grooming, the condition can become extensive, covering a large portion of the horse. The infection is highly contagious and whole groups of horses can become affected in an outbreak; young and immunocompromised horses are particularly susceptible to infection. Ringworm is also a zoonosis, meaning that people can also contract the infection and develop skin lesions.
There is a long period (up to 3 weeks) where a horse may be infective, without any clinical signs being obvious; this makes ringworm very good at spreading through a yard before it is noticed. Spores can be spread by direct contact between horses, on tack, grooming equipment and clothing etc. The spores are very resistant to destruction and can survive for many years, especially in wooden fencing and stables.