There is a total white blood cell count, and a differential count. The differential count measures the numbers of each type of white blood cell and expresses them in an absolute number and as a percentage of the total white blood cell count. The primary types of white blood cells we evaluate in dogs are neutrophils, lymphocytes, monocytes, and eosinophils. In general, we see elevated neutrophil counts with stress, infections, and inflammation. Some viral infections such as canine parvo cause neutrophil counts to be lower than normal.
Lymphocytes are a part of the immune system and can be affected by many diseases.
Certain types of cancer may cause elevations in lymphocyte numbers, while viral infections can lower lymphocyte counts. Monocyte counts above normal may be seen in some chronic fungal infections, acutely stressed animals, and hormonal abnormalities. Eosinophils are commonly elevated in parasitic diseases such as heartworm. Some allergies may also cause an increase in the eosinophil count. The final component of a CBC is the direct microscopic examination of the blood cells.