| Causes | Species Affected |
|---|---|
| Inflammation | |
| Infectious agents | |
| Bacteria: numerous species | Dog, cat |
| Fungi: numerous species | Dog, cat |
| Rickettsia: Rocky Mountain spotted fever | Dog |
| Viruses: canine distemper, feline rhinotracheitis, feline calicivirus | Dog, cat |
| Parasites: numerous species | Dog, cat |
| Protozoa: Hepatozoon americanum | Dog |
| Tissue necrosis | |
| Thrombosis/infarction | Dog, cat |
| Metabolic injury: uremia | Dog, cat |
| Physical injury: surgery, trauma, burns, frostbite | Dog, cat |
| Neoplasia | Dog, cat |
| Immune-mediated diseases | |
| Immune-mediated hemolytic anemia | Dog, cat |
| Polyserositis | Dog, cat |
| Polymyositis | Dog, cat |
| Rheumatoid arthritis | Dog, cat |
| Systemic necrotizing vasculitis | Dog (beagle) |
| Lupus erythematosus | Dog, cat |
| Physiologic leukocytosis: epinephrine release resulting from excitement, fear, exercise | Dog, cat |
| Corticosteroid-induced leukocytosis: increased endogenous or exogenous steroids, ACTH administration | Dog, cat |
| Neoplasia | |
| Leukemia: several types | Dog, cat |
| Paraneoplastic syndrome: benign and malignant tumors | Dog, cat |
| Genetic disorders: CD11b/CD18 leukocyte adhesion deficiency | Dog (Irish setter) |
| Drug administration: recombinant human or canine colony-stimulating factor | Dog, cat |
| Drug toxicity: early estrogen toxicosis | Dog |
| Miscellaneous | |
| Hemolysis | Dog, cat |
| Hemorrhage | Dog, cat |
| Toxemia/toxicity | |
| Blue-green algae toxicity | Dog |
| Botulism | Dog, cat |
| Endotoxemia | Dog, cat |
| Uremia | Dog, cat |
ACTH, Adrenocorticotropic hormone.