A low white blood cell count (WBC) results in a weakened immune system that cannot fight disease and infection. There are many causes for low WBC counts. Knowing possible causes can help determine the reason for your dog's condition.
Sick puppies with a low WBC count may have canine cyclic neutropenia, a stem cell genetic defect in all grey-coated collie puppies, suspected in all collies whose noses are not black and in some Belgian Tervurens. Physiologic leucopenia (low WBC count) in some giant schnauzers is caused by a genetic inability to absorb vitamin B.
Tick-borne diseases can result in low WBC counts in dogs, most commonly ehrlichiosis and babesiosis. If your dog has had tick bites, checking for tick-borne diseases is important.
Illness and Disease
Dogs that have been sick or had a long-term viral infection may be unable to produce enough white blood cells to replace those used. Since parvovirus attacks and kills white blood cells, dogs are often tested for it. Widespread infections or blood poisoning (sepsis) also result in lowered count.
A low WBC count can be an indication of cancer. Chemotherapy to treat cancers can also result in low WBC counts, sometimes so low that chemo must be stopped until WBC counts increase.
Some medications and chemicals can cause low WBC counts, including cephalosporin, oestrogen and human drugs such as Nexium and epilepsy medications.
If your veterinarian is unsure of the reason for your dog's low WBC count, examine each possible risk, including potential exposures to ticks or chemicals, to help determine the cause quickly.