|Mc Guire, T. - WASHINGTON STATE UNIV|
|Muller-Doblies, U. - UNIVERSITY OF ZURICH|
|Crawford, T. - WASHINGTON STATE UNIV|
Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 5, 2000
Publication Date: N/A
Interpretive Summary: Malignant catarrhal fever (MCF), a severe, globally distributed viral disease syndrome of certain ruminants such as cattle, bison, deer, is caused by a group of gammaherpesviruses. A serological test based on monoclonal antibody against a conserved component of the MCF virus was developed previously. In this study the assay was reformatted by conjugating the monoclonal antibody directly with the enzyme and by developing a method of producing precoated dried antigen plates. The changes in aggregate resulted in significant improvements in efficiency and convenience, lower cost per test, and a substantial increase in sensitivity over the original test. The greater sensitivity made the method a more reliable test for diagnosis of animals in the acute stage of clinical disease and animals with subclinical infection.
Technical Abstract: An earlier competitive inhibition ELISA (herein designated as indirect CI-ELISA) for detection of specific antibody against malignant catarrhal fever (MCF) viruses in ruminants was improved by conjugating MAb 15-A directly with horseradish peroxidase, and by developing a method of producing precoated, dried antigen plates. This new test is herein referred to as direct CI-ELISA. The reformatted test yielded a significantly improved sensitivity and reduced test duration. Of 37 MCF cases in cattle that were confirmed by histopathology and PCR, 37 (100%) were positive by the new test, whereas indirect CI-ELISA detected only 23 (62%). The direct CI- ELISA detected antibody to MCFV in 100% of 48 sheep that had been defined as infected with ovine herpesvirus 2 (OvHV-2) by PCR, whereas indirect CI-ELISA detected only 41 (85%). Comparison of antibody titers measured by the two assays in sera collected from OvHV-2 infected sheep and from cattle, bison and deer with clinical MCF revealed that direct CI-ELISA offered a 4-fold increase in analytical sensitivity over the indirect format. The number of seropositive animals detected by direct CI-ELISA among apparently normal cattle and bison was two to three times greater than the number detected by indirect CI-ELISA, indicating that a significant percentage of normal cattle and bison are subclincally infected with MCF virus.