A Retrospective Survey of Neutropenia in a Feline Referral Population in the UK
Neutrophils play an essential role in the host's innate immune response to pathogenic organisms and inflammation. Neutropenia may result from decreased production, increased consumption or destruction of neutrophils. The aim of this study was to retrospectively evaluate the aetiology of neutropenia in a population of feline patients in a UK referral hospital.
Forty two cats presenting to the University of Bristol Feline Centre between January 2002-May 2007 were identified. The age of the cats ranged from five months to thirteen years (mean 5.1years). Twenty-three cats were domestic shorthaired, five were domestic longhaired and fourteen were pedigree cats (seven breeds). Twenty-three cats were male neutered, four were male entire and 15 were female neutered.
Neutropenia was defined as a neutrophil count < 2.4 x 109/l (reference range 2.4-12.5 x 109/l). The initial neutrophil count ranged from 0.03-2.33 x 109/l (mean 1.29 x 109/l). Band neutrophils were identified in six cases (range 0.02-0.11 x 109/l) and toxic changes in two cases (both with toxic granulation and Dohlë bodies). Bicytopenia was present in 18 patients (neutropenia and anemia in 15 cats, neutropenia and thrombocytopenia in three cats), and two cases were pancytopenic. At presentation thirteen cats were hyperthermic (rectal temperature >39.2°C) and one was hypothermic (rectal temperature 37.1°C).
The aetiology of neutropenia was classified as bone marrow-related disease in 21.4% of the cases (neoplasia , myelodysplasia , maturation arrest  and aplastic anaemia ), infectious in 16.7% (FeLV , FIV , FIP  and FHV-1 ), increased demand in 16.7% (inflammatory process  and sepsis ), drug-related in 14.3% (chemotherapy induced myelosuppression ), immune-mediated disease in 19% (associated with IMHA , idiopathic neutropenia ) and was due to an undetermined aetiology in 19% of the cases (8 cats).
The most common class was bone marrow-related disease. Immune-mediated disease was diagnosed least frequently, within this group two cases of idiopathic neutropenia were identified; both cases were successfully treated with prednisolone (initial dose 1mg/kg per os BID) and were alive 21 and 24 months later. Neutropenia may be a manifestation of many disease processes, evaluation of drug history and examination for infectious, inflammatory, septic and immune-mediated disease should be made prior to bone marrow analysis to enable a diagnosis.