Causes of Leukemia
As with most other types of cancer, the causes of leukemia are not well-understood. Most leukemias in domestic dogs are thought to develop spontaneously after the dog is born. Exposure to radiation, infection by viruses and exposure to certain toxic chemical substances have all been suggested by various experts as being possible causes of or contributors to canine leukemia. However, there currently are no reliable, repeatable scientific studies that establish the contribution of these or other substances or organisms to the development of this disease.
Whatever their particular cell type or origin, leukemia cells multiply in the bone marrow and ultimately end up in circulating blood. They rapidly become space-occupying and crowd out normal bone marrow cells that otherwise would develop into healthy, mature red blood cells (erythrocytes) and white blood cells (leukocytes). This abnormal alteration of the microenvironment within the bone marrow causes a cascade of consequences, including low numbers of healthy circulating red and white blood cells. Because healthy white blood cells are essential to a normal immune response, dogs with leukemia have impaired immune systems, which in turn cause the weakness, infection and other general signs associated with the disease. Cancerous leukemia cells tend to accumulate and multiply in the spleen and liver, and to a lesser degree in the kidneys, lymph nodes, central nervous system and gastrointestinal tract. This eventually disrupts the normal function of those organs and tissues, worsening the dog’s symptoms.
Because the causes of canine leukemia are not known, there really is no realistic way to prevent the onset of this type of cancer in dogs.
Both the acute and chronic forms of leukemia are uncommon in companion dogs. However, they do occasionally occur. Acute leukemia has a much worse prognosis than chronic leukemia, with death to be expected within a matter of weeks after diagnosis in most cases.