PUTTING IT ALL TOGETHER
disease at the time the horse is showing signs of illness. There is, however, an alternative approach:
• Polymerase chain reaction (PCR). Unlike these other tests, which test a horse’s blood, bodily fluids or tissues for the presence of antibodies, PCR is a method of determining whether a disease-causing organism itself is present in the sample by identifying its DNA. PCR has myriad applications in research, but in veterinary practice it is used mainly to diagnose bacterial and viral infections that would be difficult to identify by other means. “If the pathogen is detected, it would be much more indicative of an active infection,
Lab reports based on blood tests can yield very specific and detailed information about what might be going wrong inside your horse. However, the results still need to be interpreted carefully and compared to the horse’s outward signs of illness.
“Some owners want us to come take a blood sample and tell them what their horse has, but it’s not that easy,” says Marsh. “One of the main points to remember is that doing bloodwork is just one piece of the puzzle when we are trying to figure out what is going on with that horse.”
The blood tests are part of the sequence a veterinarian goes through to diagnose a horse’s illness. “We do a physical exam, get a history, and then we can run a CBC and a serum biochemistry profile to try to determine which body system is sick,” says Wilson. “Then we might individually test for the most common diseases that would affect that body system in that particular horse, depending on his exposure to other animals, what part of the country he is in, etc. Unfortunately, you can’t just run a screening test and