Association of a retrovirus with a wasting condition in the Swedish moose.

A wasting disease in moose (Alces alces) has killed more than one thousand animals in a densely populated, limited geographical area in Sweden. To investigate the cause, local environmental conditions were studied and infectious agents, mainly viruses, were looked for. A virus, identified as a retrovirus, has repeatedly been isolated from diseased animals by cocultivation of their leukocytes with fetal moose kidney cells. The virus has the characteristics of a member of the Oncovirinae subfamily, as deduced from its morphology from EM studies, reverse transcriptase activity, cell transforming properties, and serological cross-reactivity with other oncoviruses. Striking features of the disease are the poor and transient capacity of affected moose to respond serologically in addition to the frequent presence of high levels of reverse transcriptase activity in their sera.