Until recently, the only sure way of knowing if a horse was free of lower airway disease was through endoscopy, writes Marcia King in the April edition of The Horse. But scientists in England have developed another technique that involves collecting and measuring the amount of hydrogen peroxide in the moisture of the horse's exhaled air. "Hydrogen peroxide is produced by cells within the lung that form part of the immune system," says Dr. David Marlin, head of physiology at the Animal Health Trust and a visiting professor at the University of Bristol. "In the healthy lung, very little hydrogen peroxide is produced, but when there is inflammation either due to infection (bacteria or viruses) or allergic reactions to dust and molds, the cells of the immune system produce more hydrogen peroxide. In particular, the exhaled breath condensate hydrogen peroxide is increased in proportion to the numbers of particular inflammatory cells of the body's own immune system." When an appropriate treatment is successful, the improvement is matched by a decrease in hydrogen peroxide. This approach might lead to easier and more frequent screening of horses, but is not intended to decrease or avoid the use of endoscopy, which will remain the gold standard for diagnosis, Marlin says. In other news, Dr. Andrew M. Hoffman of Tufts University is trying to develop a pulmonary function test for use in the field to measure lung capacity and gauge pulmonary impairment. Asthmatic humans already have such a test, where humans blow into a machine to determine lung capacity (as do horses), but the currently available equine test can only be conducted in a laboratory. SPINAL ATAXIA
In the movie The Lord of the Rings, Gollum was a computer-generated creature whose movements were created by filming an actor with reflective markers attached to his body. This same technology is being used at the University of Missouri-Columbia's College of Veterinary Medicine to develop a competent test in diagnosing spinal ataxia, which is a symptom of several deadly diseases in horses and can cause lameness. "Spinal ataxia is the inflammation of the spinal cord and makes the horse uncoordinated, making it very difficult for the horse to walk," said Dr. Kevin Keegan, an associate professor of veterinary medicine and surgery. "A handful of diseases cause spinal ataxia, but the problem is that spinal ataxia is very difficult to diagnose in its early stages. That is where our computer system helps." When a horse is admitted to UM-C's veterinary teaching hospital, Keegan attaches small reflective markers to the horse's body and places the animal on a treadmill. Once on the treadmill, cameras film the horse from several angles and feed data into a computer, which analyzes the movement at specific points designated by the markers. Depending on the positions of the markers as the horse moves, the camera can determine if the horse is exhibiting signs of ataxia. Some of the causes of spinal ataxia include infection of the spinal cord, malformation of the neck vertebrae, the herpes virus, and West Nile virus. When a horse has a severe case of ataxia, it is not difficult for a veterinarian to diagnose the problem. However, when the horse has just started to exhibit small signs of problems, the various tests that are currently available are expensive, may have some risk to them, and may be unreliable, according to Keegan.
"We need to have a good, accurate, reliable, diagnostic test as well as an ability to measure improvement," he said. "This computer test we have designed is an objective analysis and takes the subjective nature out of the current testing procedures. So far, we have seen a 100% diagnosis rate from the computer on the horses that we have tested." Keegan has refined the computer system so that only three markers on the horse are needed. The final stage of the project is for Keegan and his research team, composed of undergraduate and graduate students, to create a classification system.
Excerpted from The Horse: Your Guide to Equine Health Care. Free weekly newsletters at www.TheHorse.com