Neutropenia in dogs and cats: a retrospective study of 261 cases.

Case records of 232 dogs and 29 cats with neutropenia were reviewed to examine the spectrum of underlying etiologies causing the neutropenia. Six etiological categories included nonbacterial infectious disease; increased demand due to marked inflammation, bacterial sepsis, or endotoxemia; drug-associated neutropenia; primary bone-marrow disease; immune-mediated neutropenia; and diseases of unclear etiology. The largest single category associated with the development of neutropenia was nonbacterial infectious disease (e.g., feline leukemia virus [FeLV], feline immunodeficiency virus [FIV], histoplasmosis, cryptococcosis, and parvovirus), with parvovirus infection accounting for 47.1% of all cases. The least common (0.38%) cause was naturally occurring immune-mediated neutropenia.