An interpretation of Diagnostic Exercise No. 4
1. Abnormalities: in A. there are symmetrical swellings of the popliteal region in both limbs. In B. there are sharply-demarcated central zones of discoloration in both femurs. The discoloration in the top bone is pinkish-colored and extends to the growth plates; in the lower bone the discoloration is paler and not quite so extensive.. In C. the mesenteric nodes are smoothly, uniformly and hugely swollen (cut surfaces not displayed).
2. Pronounced uniform enlargement of many nodes in a young calf could possibly be due to systemic subacute inflammatory disease with heavy antigenic stimulation, but the lack of fever reduces this possibility. Likewise, severe bacterial oseomyelitis might produce necrotising inflammation of the marrow, but fever should have been present, as well as some degree of thickening of bone and/or periosteum. Lymphoid neoplasia of nodes and bone marrow can certainly involve both marrow as well as lymph nodes and produce the changes seen here, and this disease is well-recognised in juveniles.
3. So the diagnostic options: (a) juvenile sporadic bovine lymphoma with myelophthisis; (b) systemic infection with lymphadenopathy, or (c) bacterial osteomyelitis leaving the mesenteric lymphadenopathy unexplained.
4. The lymphoproliferative process in juvenile bovine lymphoma is extremely rapid. The rapid infiltration of bone marrow, as well as the lymph nodes, can corrupt the circulation of the marrow to the extent that it undergoes infarction. Probably in this case the lower bone was affected earlier than the other, but that’s a guess.
5. The animal’s lameness was probably caused by the necrotising process in the bones.