AColostrum is considered the best source of tetanus immunity for a neonatal foal. Mares are given many vaccine boosters, including tetanus, four to six weeks prior to foaling in order to provide antibody-rich colostrum. Therefore, the best approach to prevent tetanus infection in a foal is to vaccinate the mare prior to foaling and ensure adequate colostrum intake by measuring the foal’s IgG levels (immunoglobulin G, the main immunoglobulin in the mare’s colostrum that protects the foal against disease) at 12 to 24 hours of age.

Failure to vaccinate the mare or failure of passive transfer of maternal antibodies via colostrum can be remedied by vaccinating the foal at birth with tetanus antitoxin and/or administering hyperimmune plasma intravenously if the foal doesn’t receive sufficient IgG from the mare. Tetanus antitoxin provides brief, but effective, control of exposure to Clostridium tetani. However, tetanus toxoid will need to be administered and boostered in order to provide long-term protection.

It is unfortunate that your colt became infected with C. tetani and subsequently developed tetanus. Clostridial organisms, including C. tetani, which causes tetanus, and C. botulinum, which causes botulism, can infect open wounds. The umbilicus should be viewed like any fresh wound on the horse by ascertaining tetanus immunization status and cleaning the wound. Umbilical dip is used to clean the wound and can be applied several times a day until the cord becomes dry. Although tinctures of iodine are commonly employed, the best umbilical dip is a diluted (0.5%) chlorhexidine solution of four parts water to one part of 2% chlorhexidine