Response of merino sheep to inoculation with a caprine retrovirus.

Maedi-visna has never been recorded in Australia. However, caprine retroviruses have been isolated which cause clinical disease similar to caprine arthritis-encephalitis and produce antibodies in goats similar to those caused by maedi-visna virus. Merino lambs in close contact for up to 109 weeks with three goats experimentally infected with a caprine retrovirus did not seroconvert or show any significant pathological lesions. No viruses were isolated from any of these sheep though the goats seroconverted and two out of the three developed a non-suppurative bursitis and arthritis. Merino lambs inoculated with a caprine retrovirus showed no significant clinical signs or pathological lesions over a period of 140 weeks though nine out of the 12 seroconverted and viraemia was demonstrated in seven.