Hi, If it is ringworm it should respond to Lime Sulfer applied topically. You can buy it over the counter. Here is one source: http://www.thepetmedicinecompany.co.uk/equine/skincare/LimePlus-Equine-Dip-473ml--LIM001.php
Swab or spray it on twice weekly for 2 months. Yes, it can be passed on to people and other animals, so use gloves and avoid exposure as much as possible.