Owners frequently have questions about the different blood tests available for their horses. In answer to these questions, here is a brief description of common tests used in veterinary medicine and recommendations as to when tests should be run. If you have any further questions, please contact Dr. Hildebrand or Dr. Kruttlin.
Selenium is a nutrient horses need to maintain proper muscle function. Soils in Michigan have very low levels of selenium, making selenium levels in hay and grass in this state very low. In order to help horses maintain normal blood selenium levels, the nutrient is often added to grains and mineral blocks. Even with oral supplementation, some horses can have low selenium blood levels which can lead to back soreness, lameness issues, immune problems, and a dull haircoat. If your horse shows any of these clinical signs, he or she should have their selenium levels tested. Horses that have had low selenium levels in the past should also be tested once yearly. Increasing blood selenium levels can be accomplished with a combination of the right oral supplement and/or a Vitamin E and selenium injection in the muscle; however, blood levels should be checked before increasing selenium levels in the diet because high levels can also be toxic.
The Coggins test is performed to determine if your horse has Equine Infectious Anemia (EIA), a disease spread from horse to horse by biting flies. Often horses do not show signs of sickness when infected with EIA, so it is required to have proof of a negative Coggins test before changing stables, attending horse shows, or traveling between states. A horse is also required to have a negative Coggins test before changing ownership. Currently, this test is good from the time of the blood draw until Jan 1st of the following year. If you are traveling to Canada, you must have a negative Coggins test on your horse that has been drawn within 6 months.
This blood screening test helps to monitor for changes in your horse¿s kidneys, liver, and protein levels. It may be recommended by your veterinarian during times of sickness or if your horse has not been performing at normal levels or has been losing weight. This screen can often catch diseases at an early stage that may have otherwise gone undetected. It is often recommended that a chemistry profile should be run once yearly on horses over 15 years of age for reasons previously described.
A CBC test quantifies the number of red blood cells and white blood cells in your horse¿s blood. It is often drawn when a horse has an infectious disease to determine how well the horse is fighting the infection. It can also help determine if your horse is dehydrated or needs a supplement to help increase its number of red blood cells. This test is often run in conjunction with the serum chemistry profile and is also recommended to be run once yearly on horses over 15 years of age.
Hypothyroidism, low levels of thyroid hormone, can be seen in both foals and adults. Clinical signs include weakness, lethargy, poor haircoat, poor growth, and laminitis. A blood test can determine if your horse has low levels of thyroid hormone. An oral daily supplement, Thyro-L, is available to help horse¿s with hypothyroidism maintain normal thyroid levels. If your horse has been placed on this supplement, blood levels should be tested once yearly. Several blood tests may be needed over a period of 6-12 weeks in order to ensure adequate levels have been reached.
Equine Cushing¿s Syndrome is seen in older horses and ponies and is caused by changes in the pituitary gland which lead to an increase in blood steroid levels. This increase may cause horses to have a long, curly hair coat that does not shed normally, excessive sweating, abnormal fat deposits, weight loss, an increase in water consumption and urination, chronic infections, and laminitis. The test for this disease is the dexamethasone suppression test and involves drawing blood from your horse, injecting the drug dexamethasone, then drawing another blood sample 19 hours after the injection. Sometimes there are changes in the serum chemistry profile that may lead your veterinarian to suspect Equine Cushing's Syndrome and recommend the dexamethasone suppression test. If your horse has been previously diagnosed with Equine Cushing¿s Syndrome, the dex suppression test should be performed yearly to ensure steroid levels are being maintained.
EPM is a neurological disease of horses caused by the parasite Sarcocystis neurona. Horses become infected by ingesting the parasite from opossum feces deposited in hay, grain, or grass. The Western Blot blood test only determines if your horse has been exposed to the disease and not if he or she is currently infected. 60% of horses in Michigan have been shown to be positive for EPM with the blood test; therefore, results of this test should be used in conjunction with clinical signs. A positive test does not always mean your horse has EPM. Additionally, if your horse has been vaccinated with the EPM vaccine, he or she will most likely test positive for EPM. In order to have a definitive diagnosis of EPM, it may be necessary to test the fluid from around your horse¿s brain and spinal cord called CSF. To collect CSF it may be necessary to place the horse under general anesthesia which increases the risk to the horse. Often your veterinarian may use the blood test to determine whether it is necessary to perform the CSF test.