Experimental louping-ill virus infection of black grouse (Tetrao tetrix).

Louping-ill virus was injected into the tarsal pads of four black grouse and the course of infection monitored. All developed viraemia of low intensity that lasted for four days and thereafter produced high titres of haemagglutination inhibiting antibody. No clinical signs were detected and mild neuropathological changes were present in only 1/4 brains collected on day 17 after inoculation. The mild response of black grouse to infection with louping-ill virus is thus similar to that found in other woodland and forest birds and contrasts with the generally fatal response of moorland and tundra grouse species. These findings give further support to the concept that louping-ill has been introduced to the moorland habitat only in the relatively recent past.