A complete blood count (CBC) is one of the most commonly used blood tests in veterinary medicine. This test is designed to evaluate the red and white blood cells. Depending on the results of these tests, your veterinarian is able to determine the cause of your cat's illness. There are many health problems that can be determined by the number of white blood cells present in the cat's blood. An elevated white blood cell count is usually indicative of an infection; however, a low white blood cell count can signal many different health concerns for your cat.
White Blood Cells
White blood cells are the protectors of a cats body. They increase resistance to diseases, germs and infections. White blood cells produce protective antibodies that are more powerful than germs and they attack the germs in the cats body. White blood cells fight minor diseases and infections. The protective antibodies that white blood cells produce surround and demolish bacteria in the body which could make a cat sick.
There are five types of white blood cells in the body, and each has a distinct purpose. Your veterinarian will count the number of each type of white blood cells in a drop of blood; this "count" will help him determine a diagnosis.
Neutrophils, produced in the bone marrow, are essential in protecting the body against disease and infections by removing and destroying bacteria, wastes, foreign substances and other cells. Neutrophils "eat" these substances. They are the main type of white blood cell that protect the body in this way. If the level of neutrophils is too low, this is called neutropenia. Neutropenia can be caused by a severe bacterial infection that causes the formation of pus or leads to bacteria increasing in the blood. Lower levels of neutrophils can also be caused by leukaemia and aplastic anaemia.
Eosinophils are produced in the bone marrow. These cells help to fight off parasites and eat up bacteria particles in the body. Eosinophil numbers will be low if there are conditions present that cause extreme or prolonged stress.
There are two types of Lymphocytes; B cells, which produce antibodies and attach to and destroy invading organisms or other foreign materials and particles; and T cells, which memorise foreign objects and identify them in some way to the body. Lymphocytes are produced from lymphoid tissues such as the spleen and the lymph nodes. If the level of lymphocytes in the blood is low, this is called leucopenia. Leucopenia can be caused by chronic diseases such as kidney or liver failure, chronic pancreatitis and hyperadrenocorticism (Cushing's disease), as well as medications including chemotherapy drugs, prednisone and other glucocorticoids.
Monocytes develop and are stored in the spleen and bone marrow. They secrete proteins used to clean inflamed and irritated tissue, as well as eating foreign material. Monocyte levels usually do not change unless there is a cancerous leukaemia present in the cells.
Basophils, which are also produced in the bone marrow, help protect the body against disease and infections by eating some types of bacteria, foreign substances, and other cells. Basophils can be too low in cats who have severe allergies or hyperthyroidism; taking certain medications such as corticosteroids can also decrease the levels of basophils.