Preventing the spread of maedi-visna in sheep through a voluntary control programme in Finland.

The sheep disease maedi-visna (MV) was introduced into Finland in 1981 and had spread to eight flocks in the southwestern part of the country when first detected in a survey in 1994. Six more seropositive flocks were subsequently traced, bringing the total to 14. MV has a notifiable disease status in Finland that provides for official restrictive measures to which all infected herds are subject. These measures are withdrawn once the seropositive animals and their progeny are culled and the flock has showed negative signs in the test done twice, or after total culling. A voluntary control programme was initiated in January 1995 to extend official control efforts. The programme furnishes a guideline for culling, restrictions on contacts, and a timetable for testing the flock to attain MV-free status. Seven flocks of the 14 were slaughtered either immediately or after a period under restrictive measures. One flock finished sheep production after four years under restrictive measures. Selective culling and repeated testing was attempted with the other six flocks, three of which attained MV-free status. One flock finished sheep production after two years in the control programme, the other two dropped out of the programme when the restrictive measures were withdrawn. It was concluded that the control programme was salient in eradicating MV from Finland and that serological monitoring of the situation must be continuous.