A complete blood count is a diagnostic tool veterinarians use for many suspected illnesses in cats. The blood work tells the doctor the number and types of blood cells circulating in the cat's body. The results of the test can tell the doctor about many aspects of the cat's health. For example, a low white blood cell count often indicates the cat's body is fighting some type of infection.
White blood cells, known as leukocytes, are one of two types of blood cells in the body. There are always more red blood cells than white blood cells, usually 600 to 700 times more. The white blood cells' job is to defend the body against bacteria, viruses and fungi. A cat should have 4,900 to 20,000 white blood cells per microliter in her complete blood count.
A low white blood cell count can indicate several possible conditions in a cat. These include viral infections, bone marrow disorders or sepsis. The low count indicates this because the white cells have all concentrated in the area of the infection and are not circulating as they normally would--giving the low number on the test. More serious conditions involving a low white blood cell count are feline leukaemia, feline immunodeficiency virus (FIV) and distemper.
Feline leukaemia is caused by a retrovirus spread from one cat to another by saliva and respiratory secretions. Unfortunately, feline leukaemia virus spreads to the cat's white blood cells and these blood cells then spread the virus to the lymph nodes and the rest of the body. Cats with feline leukaemia often develop low white blood cell counts because of the virus. Because of this, these cats are often not able to fight off bacterial infections in an effective way.
Feline Immunodeficiency Virus
Feline Immunodeficiency Virus, FIV, is similar to Feline Leukemia in that its reproduction involves the white blood cells. The virus is carried to the cat's lymph nodes, and there it reproduces in white blood cells, which spread it throughout the rest of the body. FIV cats often have a low white blood cell count, meaning their bodies, too, have a reduced ability to fend off infections and diseases.
Distemper, also known as Feline Panluekopenia, is a decrease in the number of white blood cells. When panluekopenia, which is similar to the parvovirus in dogs, gets to the cat's bone marrow, it suppresses production of white blood cells. Again, cat are susceptible to infections and diseases if they have panluekopenia because they do not have white blood cells available to fight off illness.