Experimental Visna in Icelandic lambs.

Icelandic lambs were inoculated intracerebrally with visna virus at 10 days of age and sacrificed 22–25 days after infection. Virus was isolated from all 5 inoculated animals, and pronounced periventricular lesions, typical of early visna, were seen in the 3 lambs with the most widespread infection. The response to the infection was very similar to that seen previously in adult Icelandic sheep. In addition, 2 uninoculated lambs housed with the injected animals and sacrificed at the same time also became infected.