Equine STDs can affect pregnancy outcomes and breeding stock’s welfare.

STDs. They’re the kind of thing many people would rather not discuss. Disease transmission through sexual contact or bodily fluids such as semen and blood is still a taboo subject, even in 2012. But the reality is that as long as horse owners continue to breed their mares to stallions hundreds or thousands of miles away–or to stallions who are in their hemisphere for just a breeding season–venereal diseases have the potential to become more widespread.

These diseases can be transmitted directly between mares and stallions during natural cover and indirectly via artificial insemination (AI) or breeding equipment. Sometimes AI reduces disease spread; other times it can fuel it. Most venereal diseases aren’t life-threatening to an adult horse, but some can cause abortions in broodmares or death in young foals. Others make it difficult for mares to conceive. So from an economic as well as a welfare point of view, it’s time to cast aside any discomfort about this taboo topic and take a closer look at equine venereal diseases.

Bacterial Diseases, Including Contagious Equine Metritis

The most common venereal diseases–which are "fortunately relatively rare," says Gary M. Greene, DVM, Dipl. ACT, senior veterinarian at Greene, Lewis, & Associates equine veterinary clinic, in Covington, La.–are those caused by bacteria. What Greene sees above all in his practice is a spread of Pseudomonas and Klebsiella bacteria. These bacteria can cause endometritis (inflammation of the