Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/1995
Publication Date: N/A
Interpretive Summary: Malignant catarral fever (MCF) is an acute and fatal disease of cattle, caused by a herpesvirus. The disease is believed to be fatal and once cattle become infected, die quickly. However, we have observed some cattle may survive for a prolonged period of time after an acute attack. The clinical symptoms of MCF are often similar to that of many other cattle diseases. Thus, cattle surviving after exhibiting MCF-like clinical symptoms had been difficult to diagnose, until our recently developed diagnostic test, CI-ELISA became available. This publication concerns the demonstration that our newly developed test can readily confirm whether surviving cattle were infected with MCF virus and, for the first time, the finding of significant differences in lesions between the surviving and fatally infected cattle.
Technical Abstract: The lesions in cattle that survive acute malignant catarrhal fever for a prolonged period or appear to recover have not been documented. Six of 9 affected cattle were examined postmortem following clinical signs (CS) that developed 2-150 days earlier. Three cattle with CS for -39 days had lesions of regional lymphadenopathy and widespread severe segmental lymphoid arteritis-phlebitis that were typical of acute MCF, and proliferative intimal lesions were present in a small proportion of arteries at days 20 and 39 of CS. By contrast, 3 cattle that survived 90, 105, and 150 days after clinical onset had distinctive arterial lesions in multiple organs, characterized by proliferative concentric fibrointimal plaques, disrupted inner elastic lamina, focally atrophic tunica media, and vasculitis of variable severity. Immunohistochemical and ultrastructural examination of intimal plaques identified the predominant cellular component to be smooth muscle cells with a contractile phenotype. Serologic studies, using a CI- ELISA that detects antibody to an epitope broadly conserved among isolates of MCFV, found 2 chronically affected cattle were serologically positive between days 42 and 100 of CS, with seroconversion in 1 animal between days 52 and 73 of CS. Seroprevalence was 7.9% in the 76 remaining animals of the replacement heifer herd and 40% (75% in adult sheep and 4% in lambs) in the in-contact sheep flock 77 days after onset of CS in the index case.