Navicular disease is an ugly term in the equine world. It is a dreaded condition that makes people cringe, and if they are looking to buy your horse, they will turn and run at the first mention of the term. Before we discuss the disease, we should talk about what the navicular bone is.
The navicular bone is a small bone in the hoof. Its function is to act as a pivot point for the deep digital flexor tendon. This tendon is what brings the hoof back when the horse is moving. This little bone is not meant to bear any weight in the horse, just make it easier for that tendon to slide around the curve of the lowest part of the digit.
A while back, I gave a lecture to a small group of horse owners. I started the talk with a question. I asked,”Who here has herpes?” As expected, the room was silent. I explained that most everyone in there should have raised their hands. Ebstein-Barr virus, Chicken Pox, and of course sexually transmitted herpes are all examples of herpes viruses. Once you get them, you have them for life. In horses, it is the same. After a little explanation, everyone was laughing.
As of right now, there are 9 identified equine herpes viruses(EHV) in horses. The ones typically associated with disease are EHV 1, 3, and 4. EHV-1 , commonly called Rhinopneumonitis, can cause respiratory disease, neurological disease and abortions. EHV-3 is sexually transmitted and has symptoms similar to the dreaded venereal herpes in humans. EHV-4 is mostly just associated with respiratory disease, but can also cause abortions and neurological disease. The one everyone is talking about right now due to the recent outbreaks is EHV-1, so that is where we are going to focus.