Proud flesh is not contagious and cannot be transmitted from horse to horse. However, it can be a breeding ground for bacteria. If proud flesh is not treated properly and bacteria invade the body, the infection can be transmitted to other horses. Therefore, it is important to take great care when treating proud flesh and to make sure all exposed tissue is clean and sterile.
If proud flesh continues to grow and wraps around important structures such as tendons and bones, it can cause lameness, but proud flesh itself does not spread through the body. In fact, proud flesh can actually be beneficial to healing by keeping contaminants away from the body's vital structures.