Mortellaro is a persistent and painful infection at the back of the heel, where the 2 heels separate at the transition of skin and horn. Mortellaro is also called digital dermatitis, and is caused by the Treponema bacteria. There are more than 20 different species of the Treponema. Mortellaro is persistent, because the bacteria penetrates into the dermis. In addition, Mortellaro is very contagious to other cows.