MEADI VISNA
Visna-maedi virus from the genus Lentivirus and subfamily Orthoretrovirinae, is a retrovirus that causes encephalitis and chronic pneumonitis in sheep.
Maedi Visna is caused by a virus which is very contagious, there is no cure or vaccine and therefore it is fatal. Outbreaks have been witnessed throughout the country and of the national flock there is estimated to be at least 100,000 sheep infected.
This virus has a great impact on your flock. After clinical signs develop there is a 10-20% adult mortality. Increased lamb mortality results as well as decreased growth rates from reduced colustrum intake. Arthritis and reduced fertility occurs and causes an increase in culling rates.
Sheep do not normally show signs until they are adults as the virus has a long incubation period. The main clinical signs are:
Progressive Paralysis, Wasting, Arthritis & Chronic Mastitis.
It can be transmitted in a variety of ways:
Shedding of the virus in Milk, Colostrum, Faeces and respiratory secretions:
Lambs can be infected by drinking their mother’s colostrum or milk. A lamb stealing milk for another dam is also at risk of infection.
Other sources are contaminated water or feed when uninfected sheep are housed or at pasture with infected sheep.
