Emerging diseases… but don’t forget the old ones!

1. Emerging diseases… but don’t forget the old ones! Lynn Batty

2. What barren rate at scanning should be investigated? When should abortions be investigated?

3. Cause of increased barren rate at scanning Tup factors • Tup infertility • Poor body condition/lameness • Incorrect ewe to tup ratio Ewe factors • Poor nutrition ( trace element deficiencies) • Concurrent disease causing ill thrift including parasitism, lameness, Johnes, Maedivisna, Caseouslymphadentisand Ovine pulmonary adenomomatosis. Infectious disease • Toxoplasmosis • Border disease • Schmallenberg?

4. Common infectious cause of embryo loss, abortion and still birth Enzootic abortion (Chlamydophilaabortus) Toxoplasmosis Campylobacter Salmonella sp Listeria Border disease Schmallenberg These can also cause the birth of weakly lambs

5. Schmallenberg virus • Orthobunyavirus identified in 2011 • First identified in the UK in January 2012 • Infection of susceptible sheep usually subclinical. • Causes abortions and stillbirths with foetal deformities including immobile joints, brain abnormalities and narrowing of spinal cord. Dummy lambs born on farms with abnormalities. • Spread by midges • Risk period 20-60 days gestation. • Variable dates quoted as risk period.

6. Schmallenberg virus – Does previous infection on the farm mean the flock is immune? • No- The degree of exposure to SBV cannot be predicted by location and history. • The proportion of sheep in a flock that become infected and develop immunity following natural infection via midges is more variable than in cattle. • Recent studies have suggested that flocks can contain a significant population of susceptible sheep even after two seasons of exposure.

7. Schmallenberg virus – Does previous infection on the farm mean the flock is immune? • Flocks in Sussex, Essex and Kent that were previously exposed had varying seroprevalence from 8% - 73%. [Study by Nanajiani et al (2013)] • Another study in SW England looked at seven flocks with previous exposure. Lamb losses from Schmallenberg ranged from 4-40%. Seroprevalence varied in these flocks from 35% to 94%. [Study by Glover (2013)] NATURAL IMMUNITY CANNOT BE RELIED ON TO COMPLETELY PROTECT A FLOCK FROM LOSSES FROM SBV.

8. Schmallenberg virus- is there a vector free period? • Cases of deformed calves confirmed to be caused by SBV seen in Aberdeenshire in June suggesting that midges were circulating in late autumn- early winter. • Cases of active infection in adult sheep in Dartmoor managed outdoors in mid March. • Risk periods:

9. DON’T ASSUME ALL DEFORMED AND DUMMY LAMBS ARE DUE TO SCHMALLENBERG!!!!

10. Border disease • Pestivirus related to BVD virus. • Sheep to sheep contact principal mode of transmission. Bought in carriers likely source of infection • Adults and healthy lambs exposed to Border disease only have mild clinical signs. • Sheep are potential low risk for spreading Border disease to cattle. A higher risk is cattle spreading BVD to sheep • Serious consequence if sheep are naïve and infected during pregnancy

11. Border disease Clinical signs: • Poor scanning percentage • Increased abortions and stillbirths • Weakly lambs born • “Hairy shakers”

12. Border disease

13. Border disease: Why should you worry? • SAC study 2006: 125 flocks in Scotland tested1 in 3 flocks there was evidenceof exposure to Border disease. ? An increasing threat to the sheep industry ? Consequences to the pedigree flock if Border disease introduced: • Losses at lambing • Potential loss of reputation if persistently infected(PI) lambs sold • Cost of testing to find PI animals

14. What can be done? • Investigate increased abortion/ still births, deformities or dummy lambs. • Screening tests involve antibody testing of young sheep e.g. hoggs/gimmers to assess the flock status. • If positive consider virus testing to find a PI • Consider testing of replacement breeding stock.

15. Reduced lambing percentages? • Poor lamb growth rates? • Lower weaning weights? CONSIDER MAEDI VISNA

16. Maedivisna • Virus infection • Maedi– pneumonia • Visna – wasting • Persistent, lifelong infection • Long incubation period • Often fatal • No cure or vaccination

17. Clinical signs • Weight loss • Pneumonia • Mastitis • Arthritis • Hindlimb paralysis

18. Flock example • 1500Masham ewes • Single bearing ewes in poor body condition • Lower lambing percentage • Increased no. of thin ewes & deaths • Smaller lambs & lower milk yield => poorer lamb growth rates, lower weaning weights

19. Flock example • 4 out of 6 ewes positive for MV • Difficult to fatten cull ewes • Higher replacement rate in recent years • Suspect bought in ~ 8 years earlier

20. Flock example - economic effects • 20-40% reduction in productivity • £30-50k cost p.a. & ongoing Aug 2012 update: • Losing an average of a ewe a day • Low milk yields • Very uneven lamb crop

22. SAC/AHVLA MaediVisna survey findings - funded by EBLEX & HCC

23. Summary • Consider investigating: • Lower scanning rate percentages (<5% barren) • Abortion and still births (<2%) • Discuss appropriate investigation with your vet. • Reach a diagnosis and instigate appropriate treatment or eradication. • Prevent the disease from entering the flock by health planning. • If you don’t have a disease keep it out by quarantine of new stock and testing for disease where appropriate.

24. Any questions?