Prospective Hematologic and Clinicopathologic Study of Asymptomatic Cats With Naturally Acquired Feline Immunodeficiency Virus Infection

Shelton, Grady H.; Linenberger, Michael L.; Persik, Monica T.; Abkowitz, Janis L.

Prospective studies were performed over a 28‐ to 77‐month period (median, 66 months) on 5 cats with naturally acquired feline immunodeficiency virus (FIV) infection in an attempt to correlate hematologic and Clinicopathologic changes with the emergence of clinical disease. On presentation, all cats were asymptomatic; free of opportunistic infections; and had normal complete blood counts, bone marrow morphologies, marrow progenitor frequencies, and progenitor in vitro growth characteristics. During study, 2 cats remained healthy, 2 cats showed mild clinical signs, and 1 cat developed a malignant neoplasm (ie, bronchiolar‐alveolar adenocarcinoma). Although persistent hematologic abnormalities were not observed, intermittent peripheral leukopenias were common. In 3 of 5 FlV‐seropositive cats, lymphopenia (< 1,500 lymphs/μL; normal reference range, 1,500 to 7,000 lymphs/μL) was a frequent finding and the absolute lymphocyte counts had a tendency to progressively decline. One of the other 2 cats had consistently low to low‐normal absolute neutrophil counts (1,300 to 4,800 segs/μL; mean, 2,730 segs/μL; normal reference range, 2,500 to 12,500 segs/μL), and the remaining cat had consistently normal leukograms, except for a transient period (ie, 11 months) of benign lymphocytosis (7,200 to 13,430 lymphs/μL) early in the study. Periodic examinations of bone marrow aspirates revealed normal to slightly depressed myeloid‐to‐erythroid ratios with normal cellular morphology and maturation. Bone marrow abnormalities observed late in the study included mild dysmor‐phic changes (ie, megaloblastic features) in 2 cats, and a significant decrease (60% of controls, P < .001) in the frequencies of burst‐forming units erythroid (BFU‐E) in marrow cultures of FIV‐seropositive cats compared with uninfected control cats. Serum biochemical profiles were unremarkable throughout the study, with the exception of hyperglobulinemia (ie, polyclonal gammopathy) in 2 of 5 cats. Peripheral blood and bone marrow findings were of no apparent prognostic value. These results confirm the long latency between natural FIV infection and the development of life‐threatening clinical disease. Chronic FIV infection, like infection with human immunodeficiency virus, can be associated with derangements in peripheral blood cell counts, as well as pertubations in marrow cell morphologies and hematopoietic progenitor frequencies before the terminal symptomatic stages of retroviral disease, when persistent cytopenias are prominent.