Experimental transmission of malignant catarrhal fever in cattle: gross and histopathologic changes.

Bovine malignant catarrhal fever (MCF) was serially transmitted from a spontaneous case to 19 cattle through 12 passages during a 12-month period. Seventeen of 23 cattle (74%) injected with whole blood and 2 of 5 cattle (40%) injected with blood mononuclear cells developed clinical signs of MCF after a mean incubation period of 30.2 days. A previously unreported nonsuppurative polyarthritis is described. Large numbers of lymphoid cells were found in synovial fluid and in cerebrospinal fluid. Histopathologic changes of lymphoid infiltration and proliferation, necrosis of epithelial tissues, and nonsuppurative vasculitis were found in almost all organs of the body. The possibility that MCF may be a viral-induced, cell-mediated immunopathologic disease with pansystemic lymphoreactivity and necrosis is discussed.