INCREASE IN MV

I would like to draw your attention to an increase in the level of Maedi Visna (MV)
in the country. In previous years, MV accreditation scheme testing identified
evidence of MV infection in an average of three MV accredited flocks per year
however in 2010 there were 13 breakdowns with MV. We have already identified
two breakdowns in the first quarter of 2011 but the main test season is May to
September. Since the start of 2010 we have also identified MV infection in five
groups/flocks of sheep that were going though qualifying tests in order to become MV accredited.
The following breeds have been identified as being positive for MV in these cases: Texel, Charollais,
Zwartble, Clun Forest, Border Leicester, Mule, Suffolk, Wiltshire, Lleyn and Beltex cross. In one case
infection was introduced when non-MV accredited ewes were introduced to a flock as foster mothers.
Fortunately their routine periodic blood test was due two months after these sheep were introduced so the
infection was detected at an early stage. However it could have been much more serious as the flock is on
every three year testing so infection could therefore have gone undetected for up to three years and have
spread to many other flocks in the interim. In other cases risk factors have included:
· possible contact with non-MV accredited sheep through single gates and inadequate fences (the
rules state that a minimum two metre gap is required between MV accredited and non-MV
accredited sheep at all times)
· the use of non-MV accredited semen
· contact with straying cull ewes
· being housed in the same shed as non-MV accredited sheep
· break-in of sheep from infected neighbouring flocks
A MV accredited flock which has non-MV accredited sheep on the same holding has over twice the risk of
a breakdown compared to a holding with solely MV accredited sheep. In these cases the main route of
infection is likely to be contact with non-MV accredited sheep through inadequate fences/gates but sharing
of equipment is also a risk.
It takes a minimum of 12 months, and there are significant test costs, in order to regain MV accredited
status following a breakdown with MV. However the cost involved in eliminating infection is much less
than the long term costs of disease in an infected flock.
A case was recently highlighted in the farming press where the owner of a 1500 ewe commercial flock has
estimated that MV has reduced his flock’s output by 20-40% and as a result is costing £30,000-£50,000 per
annum.
Catriona Ritchie, MV Veterinary Manager, PSGHS

SAC Consulting Veterinary Services
All of the MV accreditation scheme rules
and application forms are on the website
at www.sac.ac.uk/sghs . The phone
number for the Premium Sheep & Goat
Health Schemes office is 01463 226995