This section is from the book "The Farmers Ready Reference Or Hand Book Of Diseases Of Horses And Cattle", by S. C. Orr. . Also available from Amazon: The Farmer's Ready Reference;.
Small lumps or pimples the size of a pea or larger come on the skin on any part of the body or limbs; these itch, and, by rubbing, a raw sore is produced which increases in size, becomes hard or caked, and a bloody serum oozes out. Because of severe itching the horse continues to rub and bite the sore until a surface several inches in diameter is often involved. These sores are due to a parasite (Filaria irritans) which must be destroyed before permanent healing can take place.
Treatment. - Shower the part for half an hour with cold water, then sponge it over thoroughly with chloroform until every part has been saturated, after which apply a coating of the following: Calomel, one ounce; tannic acid, one ounce; vaseline, four ounces; mix. This entire treatment must be repeated faithfully every day until the sore is all healed. The animal must be prevented from biting the sore.