Let's Run Some Bloodwork...
There are many times when we recommend running bloodwork on your horse. Most commonly as veterinarians we see sick horses with fevers, horses with strange behavior and older horses with long, heavy coats and excessive drinking and urinating. Other times we see healthy but stressed, traveling horses with heavy work and show schedules. Sometimes horses are just ADR: Ain't Doing Right, for seemingly no good reason. The following is a description of the major types of bloodwork that we run and what they tell us.
Complete Blood Count
Blood has three separate components: White Blood Cells, Red Blood Cells, and Plasma.
A complete blood count, generally referred to as a CBC, quantifies your horses' total white blood and red blood cell counts. On sick horses we are most interested in the total white blood cell count and fibrinogen, which is an equine specific marker indicative of systemic inflammation. White blood cells are also broken into various other specific cell types including neutrophils, basophils, monocytes, eosinophils, lymphocytes and platelets. Relative fluctuations in these individual parameters can help us to determine what is going on with your horse.
Red blood cells are the other cellular component of blood. Red Blood cells (RBC) can be low and indicate anemia or high and indicate dehydration. Hematocrit is a relative RBC parameter that we use in combination with kidney values to evaluate the hydration status of your horse.
When To Run:
Fevers: WBC count can be either high or low. High WBC counts are more commonly seen with entrenched bacterial infections such as strangles and pneumonia. Horses with acute infections of the blood and gastrointestinal tract, and those with Erlichia/Anaplasma, typically exhibit a lower WBC.
Traveling/Showing: Screening tests on heavily scheduled horses can help shed light on subclinical immunosuppression that may be contributing to decreased performance and making horses more susceptible to communicable diseases when in contact with unfamiliar horses.
Serum Chemistry
This test quantifies a large number of the most important major organ markers and electrolytes. Most commonly we are looking at the Kidney markers BUN (blood urea nitrogen) and Creatinine (Cr) to gauge your horse's kidney function. LDH/AST/ALP, Bilirubin, and total protein (TP) are indicators of liver function. Creatinine Kinase (CK) is a muscle enzyme we evaluate when we are concerned a horse may have a muscle disorder such as exertional rhabdomyolysis (tying-up syndrome)
When To Run:
Usually we run this along with the CBC so we have a complete picture of the horse's systemic situation. NSAIDS: such as bute, banamine, and more recently firocoxib (Equioxx/Previcox) are commonly given to horses and can cause significant kidney damage (elevated BUN/Cr) if given for long periods of time or in high doses.
Fevers: will sometimes exhibit renal and liver changes either primarily or in response to heavy treatment with NSAIDS for temperature control.
Colic: can be dehydrated with elevated kidney and RBC parameters (BUN/Cr/TP/Hematocrit). Some chronic colics can be caused by primary liver and bile tract disease and will present with significantly elevated liver values. Right Dorsal Colitis with diarrhea and/or mild colic is a result of stress, antibiotic or chronic NSAID treatment and can be hard to definitively diagnose. A low serum protein (TP) can indicate protein loss from the blood into the gut due to an inflamed colon wall.
Muscle Disease: low grade performance issues and in those who are actively tying up will exhibit a marked increased in CK (sometimes 100,000x normal!) and potentially AST. These horses may also have elevated kidney values (BUN/Cr) as the breakdown products of muscle are toxic to the kidneys. This is a critical situation and requires heavy fluid therapy to prevent serious kidney damage.
Geriatrics: Sometimes horses are just old and their organs are not as equipped to keep up with the stresses of their environment. It is good to know of underlying kidney or liver disease in an older horse which may require medical intervention or simply to aid us in selecting a modified medication protocol to ensure a safe and successful outcome.
ACTH is a hormone produced by the pituitary gland in the brain. Overproduction is seen in horses with Pituitary Pars Intermedia Dysfunction (PPID), more commonly referred to as Cushing's disease. These horses tend to be over 15 years of age, overweight, exhibit a characteristically long, heavy, curly haircoat and excessive drinking and urinating. Less frequently horses can exhibit dramatic muscle loss, usually of the top line, and difficulty building muscle and gaining weight. Sometimes inability to heal infections or chronic hoof abscesses can indicate immunosuppression which is a side effect of high circulating levels of ACTH in the blood. ACTH is a fragile chemical and must be submitted only as a frozen plasma sample. This requires that we separate the plasma (the third blood component) from the red and white blood cells and freeze in a timely manner.
