Cytological evaluation of bone marrow in 11 cattle with enzootic bovine leukosis.

As the frequency and significance of bone marrow (BM) infiltration in enzootic bovine leukosis (EBL) remain unclear, this study evaluated BM involvement and its relationship with peripheral blood (PB) findings in 11 cattle with EBL using PB evaluation, and BM aspiration cytology. BM infiltration was identified in 5 of 11 (45%) EBL cases based on BM smears. All EBL cases showed circulating atypical lymphocytes, although BM infiltration was not consistently present. Two cases with extreme PB lymphocytosis showed BM infiltration. Cytopenia was variably observed and was most severe in cases with extensive BM involvement. This study provides combined assessment of PB and BM changes in EBL cattle and suggests that such evaluation enables a more comprehensive characterization of hematological alterations.