[The etiology of "malignant catarrhal fever" originating in sheep: serological findings in cattle and sheep with ruminant gamma herpesviruses].

In the case of the wildebeest-derived form of malignant catarrhal fever (WD-MCF) alcelaphine herpesvirus 1 (AlcHV1) is well established as the cause. However, the etiology of the form of the disease circumstantially associated with sheep (SA-MCF) remains equivocal. A serological relationship has been proposed to exist between the unidentified sheep-associated agent causing SA-MCF and AlcHV1 causing WD-MCF. We attempted to confirm this hypothesis. Using an indirect ELISA we found 94 of 100 cattle (94%) and 80 of 90 sheep (89%) to display antibody to AlcHV1. Nine of 10 cattle with SA-MCF showed elevated antibody titers to AlcHV1 when compared with most other animals. However, these findings were of limited diagnostic value, since similar results were also obtained with sera from healthy cattle. When assayed in the presence of antigens of bovine herpesvirus 4 (BHV4), a virus related to AlcHV1 yet without confirmed pathogenicity, 99 cattle sera (99%) and 85 sheep sera (95%) were observed to react specifically with this virus. Together, the results indicated that most domestic cattle and sheep were infected with viruses that are related to AlcHV1 and BHV4. An etiologically meaningful interpretation of the serologic findings does not seem possible at present.