PROSPECTIVE HEMATOLOGIC AND CLINICOPATHOLOGICAL STUDY OF ASYMPTOMATICCATS WITH NATURALLY ACQUIRED FELINE IMMUNODEFICIENCY VIRUS-INFECTION

Prospective studies were performed over a 28- to 77-month period (medi an, 66 months) on 5 cats with naturally acquired feline immunodeficien cy virus (FIV) infection in an attempt to correlate hematologic and cl inicopathologic changes with the emergence of clinical disease. On pre sentation, all cats were asymptomatic; free of opportunistic infection s: and had normal complete blood counts, bone marrow morphologies, mar row progenitor frequencies, and progenitor in vitro growth characteris tics. During study, 2 cats remained healthy, 2 cats showed mild clinic al signs, and 1 cat developed a malignant neoplasm lie, bronchiolar-al veolar adenocarcinoma). Although persistent hematologic abnormalities were not observed, intermittent peripheral leukopenias were common, In 3 of 5 FIV-seropositive cats, lymphopenia (<1,500 lymphs/mu L; normal reference range, 1,500 to 7,000 lymphs/mu L) was a frequent finding a nd the absolute lymphocyte counts had a tendency to progressively decl ine, One of the other 2 cats had consistently low to low-normal absolu te neutrophil counts (1,300 to 4,800 segs/mu L; mean, 2,730 segs/mu L; normal reference range, 2,500 to 12,500 segs/mu L), and the remaining cat had consistently normal leukograms, except for a transient period tie. 11 months) of benign lymphocytosis (7,200 to 13,430 lymphs/mu L) early in the study. Periodic examinations of bone marrow aspirates re vealed normal to slightly depressed myeloid-to-erythroid ratios with n ormal cellular morphology and maturation. Bone marrow abnormalities ob served late in the study included mild dysmorphic changes lie, megalob lastic features) in 2 cats, and a significant decrease (60% of control s, P < .001) in the frequencies of burst-forming units erythroid (BFU- E) in marrow cultures of FIV-seropositive cats compared with uninfecte d control cats. Serum biochemical profiles were unremarkable throughou t the study, with the exception of hyperglobulinemia (ie, polyclonal g ammopathy) in 2 of 5 cats. Peripheral blood and bone marrow findings w ere of no apparent prognostic value. These results confirm the long la tency between natural FIV infection and the development of life-threat ening clinical disease. Chronic FIV infection, like infection with hum an immunodeficiency virus, can be associated with derangements in peri pheral blood cell counts, as well as pertubations in marrow cell morph ologies and hematopoietic progenitor frequencies before the terminal s ymptomatic stages of retroviral disease, when persistent cytopenias ar e prominent. Copyright (C) 1995 by the American College of Veterinary Internal Medicine.