Between 1998 and 2000, 103 individuals of 19 species of the order Artiodactyla at Whipsnade Wild Animal Park were tested for evidence of infection with gamma herpesviruses in order to distinguish between species which are susceptible to malignant catarrhal fever (MCF), caused by alcelaphine herpesvirus-1 (AlHV-1) of wildebeest ( Connochaetes sp.) or ovine herpesvirus-2 (OvHV-2) of domestic sheep, and species which carry related viruses sub-clinically. Gamma herpesvirus DNA was detected in the known, or suspected, carrier species: roan antelope ( Hippotragus equinus), scimitar-horned oryx ( Oryx dammah), gemsbok ( Oryx gazella), musk ox ( Ovibos muschatus) and mouflon ( Ovis musimon). In six other species: lowland anoa ( Bubalus depressicornis) yak ( Bos grunniens), sitatunga ( Tragelaphus spekei), greater kudu ( Tragelaphus strepsiceros), waterbuck ( Kobus ellipsiprymnus) and Nile lechwe ( Kobus megaceros), DNA was present in some newborn calves and over 30% of adults, strongly suggesting a carrier state. In contrast five Père David's deer ( Elaphurus davidianus) and two swamp deer ( Cervus duvauceli) died of MCF during the study. A virus isolated from scimitar-horned oryx calves produced cytopathic effects in scimitar-horned oryx kidney cell-culture and caused MCF in a rabbit.