64 Neutropenia
Neutropenia in the dog is defined as less than 2.9 × 109 neutrophils per liter.
The following are the three main categories of causes for neutropenia:
Chemotherapeutic, immunosuppressant, or other drugs, irradiation, toxins, infections such as canine parvovirus or ehrlichiosis, stem cell disorders, marrow fibrosis, or myelophthisis are all potential causes of decreased neutrophil production in the dog.
A cyclic neutropenia, typically accompanied by cyclic decreases in the products of other cell lines, is a documented congenital abnormality seen in some Gray Collies or Gray Collie crosses. It is suspected that this disorder is the consequence of a defect in granulocyte colony-stimulating factor postreceptor signal transduction.
Acute severe inflammatory conditions, often caused by Gram-negative bacteria can result in neutropenia from an increase in the efflux of neutrophils from the circulating pool into the tissues.
Immune-mediated neutrophil destruction is possible and may be idiopathic (primary) in nature, or secondary to drug administration, infection, neoplasia, or other concurrent immune-mediated disease. Immune-mediated neutrophil destruction has not been well documented in the dog.
