Maedi Visna (MV) virus infection is becoming more commonly diagnosed as a cause of major production and economic losses in commercial flocks and is an increasing threat to the UK sheep industry. The importance of MV accredited flocks should not be understated. Accredited Lleyn flocks are in demand as a source of MV free animals.
‚ÄúI was impressed from the very first time I saw the Lleyn ewes‚ÄĚ says Jimmy Law who farms at Baillieknowe near Kelso. Unfortunately their Greyface flock was wiped out by MV in the summer of 2017 so they decided to source MV accredited Lleyn replacements.
Jimmy refers to it as the perfect storm! They scanned the original flock of mules last Jan at 215%. ‚ÄúThe ewes looked in fantastic fettle but within a month after housing they were all skin and bone‚ÄĚ commented Jimmy. They put it down to the stress of housing at lambing time and they were also aware the flock had problems with OPA (Ovine Pulmonary Adenocarcinoma) also known as Jaagsiekte.
The flock was blood tested after lambing and they found 61% of the flock was infected with MV. Following a meeting in May between the flock owner, land agent, Jimmy and vets they decided to cull the entire Greyface flock. ‚ÄúThere were just too many infected sheep to attempt to separate out infected animals from non infected animals‚ÄĚ Jimmy explained. ‚ÄúThe financial loss was massive! We only got fat value for 800 breeding mules and Texel tups! - it was a traumatic year - farmers simply don‚Äôt appreciate how bad it is!‚ÄĚ
Farm Health Overview
‚ÄĘ The flock had had an ongoing problem with poor milk production in ewes with lambs taking longer to finish.¬†
‚ÄĘ At tupping time 7% of the ewes were found to have signs of chronic mastitis.
‚ÄĘ Ewes were in good condition at scanning time but by lambing around 50% were in poor body condition and had insufficient milk supplies.
‚ÄĘ Due to this a large number of lambs had to be reared on artificial milk and took longer to finish requiring supplementation with creep feed.
‚ÄĘ As part of the investigation post mortem examinations of three ewes were performed by the local Veterinary Investigation Centre and MV infection was confirmed in all three.
A source of accredited mules could not found and the decision was made to restock with MV accredited Lleyns. Jimmy managed to source MV accredited replacement Lleyns just 6 miles away. The sellers were cutting down numbers due to their shepherd‚Äôs ill health so they bought all their ewes and tups from them and plan to operate a completely closed flock operating a family system of breeding. Jimmy who is preparing to lamb their new Lleyn flocks says ‚ÄúI thought MV accreditation was a bit of a gimmick for selling sheep until last year! It all happened so quickly ‚Äď within 6 weeks!‚ÄĚ They are now members of SAC‚Äôs Premium Sheep and Goat Health Scheme.
MV infection can cost ¬£30/ewe in lost production in commercial flocks (higher in Pedigree flocks) but ¬£1000s if the infection means a complete re stock!
It is likely with more commercial flocks being diagnosed with MV that accredited Lleyn flocks are going to increasingly be relied on as a source of MV accredited sheep and an alternative to mules in restocking.
MV Facts and Symptoms
‚ÄĘ The words ‚Äėmaedi‚Äô and ‚Äėvisna‚Äô are Icelandic words meaning ‚Äėgasping or panting‚Äô and ‚Äėshrinking or wasting‚Äô respectively
‚ÄĘ MV was introduced into the UK through imported sheep over 30 years ago
‚ÄĘ It has a long incubation period and is subtle and slow to develop
‚ÄĘ Symptoms include weight loss, breathlessness, mastitis and reduced milk yield and swollen joints
‚ÄĘ Production losses may include poor lambing percentages and reduced lamb weaning weights.
‚ÄĘ Transmission is via nose to nose contact, colostrum and infected equipment
‚ÄĘ It is fatal, with no current cure or vaccine available.
‚ÄĘ MV is difficult to diagnose due to its long incubation period and the fact clinical signs are often not seen until at least 50 per cent of the sheep in a flock are infected. It is possible to carry out a blood test for the antibody to MV
‚ÄĘ An initial screen of 12 cull ewes will tell you if MV is the likely cause of disease in your flock.
‚ÄĘ The longer the disease circulates in your flock the harder it will be to eradicate or control it and the more impact it will have on your flock‚Äôs productivity
‚ÄĘ To keep MV out of a flock, only purchase breeding replacements from MV accredited flocks and avoid contact with MV-positive stock