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United States Department of Agriculture

Agricultural Research Service

Title: Field Validation of Laboratory Tests for the Clinical Diagnosis of Sheep Associated Malignant Catarrhal Fever

Authors
item Muller-Doblies, U - U OF ZURICH
item Li, Hong
item Hauser, B - U OF ZURICH
item Adler, B - U OF ZURICH
item Ackermann, M - U OF ZURICH

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 1998
Publication Date: N/A

Interpretive Summary: Until recently, the diagnosis of the sheep-associated form of malignant catarrhal fever (SA-MCF) relied mainly on the clinical picture and the histopathological lesions. In this study, we compared and evaluated two recently-developed assays (PCR for MCF viral DNA and a CI-ELISA for the viral antibody) with histoppathology for the diagnosis of MCF using 44 clinically diagnosed MCF flied cased and samples from over 100 clinically healthy cattle. Based on histopathology, 38 of the 44 clinical cases were classified as "MCF positive", 3 were classified as "inconclusive" and 3 cases as "MCF negative". The test values of PCR and CI-ELISA were assessed in relation to histopathology as a provisional "gold standard". The cases neither clearly positive nor clearly negative were therefore once considered positive and once negative to assess a worst and best case scenario. Healthy animals were not examined by histopathology, but were assumed to be negative in histopathology for the test comparison: The sensitivity of the PCR was 95 to 97%, whereas the specificity ranged between 94 and 100%. The CI-ELISA showed a sensitivity of 56 to 87% and a specificity between 91 and 100%. In the field, there is a good correlation between the diagnosis of MCF by histopathology, PCR, and CI-ELISA, respectively. These data also confirm the close association of ovine herpesvirus 2 with SA-MCF in Switzerland.

Technical Abstract: Until recently, the diagnosis of the sheep-associated form of Malignant Catarrhal Fever (SA-MCF) relied mainly on the clinical picture and the histopathological changes. Using clinically diagnosed field cases, we have evaluated two recent methods, i.e. a seminested PCR and a competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) and compared these assays with histopathology in the diagnosis of clinical SA-MCF in cattle. Samples from 44 cattle with clinical signs suggestive of MCF were examined by histopathology, PCR and CI-ELISA. In addition, samples from healthy cattle were also evaluated by PCR (n=96) and CI-ELISA (n=75). Based on histopathology, 38 of the 44 clinical cases were classified as "MCF positive", 3 were classified as "inconclusive" and 3 cases as "MCF negative". The test properties of PCR and CI-ELISA were assessed in relation to histopathology as a provisional ¿gold standard¿. The cases neither clearly positive nor clearly negative were therefore once considered positive and once negative to assess a worst and best case scenario. Healthy animals were not examined by histopathology, but were assumed to be negative for the test comparison: The sensitivity of the PCR was 95 to 97%, whereas the specificity ranged between 94 and 100%. The CI-ELISA showed a sensitivity of 56 to 87% and a specificity between 91 and 100%. In the field, there is a good correlation between the diagnosis of MCF by histopathology, PCR, and CI-ELISA, respectively. These data also confirm the close association of Ovine Herpesvirus 2 with SA-MCF in Switzerland.

Last Modified: 12/22/2014
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