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Blue Tongue and Foot and Mouth Disease BWBL Seminar 20.11.12

Blue Tongue and Foot and Mouth Disease BWBL Seminar 20.11.12. David Hucker B.V.Sc. M.A.N.Z.C.V.Sc. Blue Tongue Virus. Transmitted by Midges ( Culicoides spp ) Causes fever, abortion, breathing and circulation problems(hence blue tongue)

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Blue Tongue and Foot and Mouth Disease BWBL Seminar 20.11.12

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  1. Blue Tongue and Foot and Mouth DiseaseBWBL Seminar 20.11.12 David Hucker B.V.Sc. M.A.N.Z.C.V.Sc.

  2. Blue Tongue Virus • Transmitted by Midges (Culicoides spp) • Causes fever, abortion, breathing and circulation problems(hence blue tongue) • Mortality 0% in accustomed sheep to 90% in susceptible sheep • Are at least 16 strains of BTV

  3. Blue Tongue Virus • Has been in NT sentinel sheep since 1970s? (maybe 1956) • Reservoir of infection in Africa and M. East • Moved into Northern Europe in 2006-8

  4. BTV Movement into Europe 2006-8

  5. BTV Movement into Europe 2008

  6. Concerns • Spread into N Europe • Similar or higher latitude than all of Australia • Some Culiciodes spp in N Europe are here in Vic • Appears to over winter in N Europe then re-emerge • Possibly due to transplacental hibernation????

  7. What about Australia? • Insects eg Culicoides float into Australia periodically from Timor and Papua New Guinea • Can carry arbo viruses eg Blue Tongue, Aino, Akabane and ??Schmallenberg?? • BTV 2 identified in sentinel sheep in NT 2009 • By 2010 BTV 2 was identified in Qld – How did it get there?

  8. Is this a risk for Australia? • Blood from Qld passaged in a sheep at AHL, Geelong 2010 • Sheep severely affected with BTV by day 12 and had to be euthanased • Blood from this sheep used to infect 3 sheep in sentinel flock in NT • All became severely affected and were euthanased Source: nunetherlands.com

  9. Should we be concerned ? • Culicoides spp • In Europe Culicoides imicola was main vehicle for spread • In Australia, Culicoides brevitarsus likely to be main transmitter. • These two species of Culicoides are very similar • Normal biosecurity measures on farm will have little effect on flying insects

  10. What can we do? • Control possibilities • Vaccine – is strain specific and will take 9 months to produce once infection confirmed • Culicoides brevitarsus (suspected to be main transmitter in Australia) reproduces in cattle dung. • Culicoides susceptible to Ivermectin • Therefore may be possibility of controlling vector by treating cattle with ivermectin

  11. Management of BTV • Vaccination • UK • killed vaccine • $2 per head yearly • South Africa • Live attenuated vaccine • Once in a lifetime • But vaccine can be infective • Insect Control • House sheep at night? • Ivermectin???

  12. Foot and Mouth Disease

  13. Foot and Mouth Disease in Australia • Until now - Control by Eradication or Stamp Out • But after UK 2001 Governments wary of adverse publicity

  14. Foot and Mouth Disease • Australia now leaning towards Vaccination • International symposium in Melb in May 2010 • International workshop on FMD outbreak • How would vaccine be used? • When? • What issues may arise? Source: MSD animal health

  15. Foot and Mouth Disease • Vaccination • There are 7 strains of FMD – Vaccine needs to be the right strain • Australia has agreement with Merial UK to supply 500 000 doses of oil adjuvant vaccine (will give +ve blood tests for about 12 months) • Will take about a week to prepare vaccine • This will be enough to cover a small ring vaccination of one outbreak only • Depending on type, more vaccine may be available from UK

  16. Foot and Mouth Disease • Diagnosis • Blood tests look for antibodies = evidence of infection • But both natural infection and vaccination cause antibodies • How can we tell vaccinated from infected animals? • DIVA test = Differentiate between Infected and Vaccinated Animals

  17. Foot and Mouth Disease • Diagnosis by DIVA tests • More highly purified vaccines antibodies can be differentiated using monoclonal and polyclonal antibody reagents – Not good enough for the 2001 UK outbreak but used in 2001 Uruguay outbreak • Recombinant antibody tests developed by CSIRO in 2007 are now better and cheaper

  18. Foot and Mouth Disease • Trade Issues (OIE) • Trade prohibited for 3 months after last case • Extensive surveillance needed to prove this • Only once has this been achieved so usually much longer • Trade prohibited for 3 months after last case or vaccinated animals slaughtered • Extensive surveillance needed to prove this • Trade prohibited for 6 months after last case OR vaccination withdrawal (animals allowed to live) • If using this method need DIVA testing and surveillance

  19. Foot and Mouth Disease • Trade Issues • Outbreak could be expected to last up to 2 years before trade can resume • What do we do with the slaughtered animals? • Can’t export and we can’t eat that many • Effect on stock values? • Will be a real problem!

  20. Foot and Mouth Disease(a tale of two outbreaks) • UK Feb 2001 outbreak was well publicised • Uruguay May 2001 outbreak almost unheard of

  21. Foot and Mouth Disease(a tale of two outbreaks) • Final outcome after eradication Note: Only cattle vaccinated in Uruguay. 24 million doses of vaccine used in Uruguay

  22. Conclusions • Blue Tongue Virus • May be more of a threat to Southern sheep areas than previously thought • Foot and Mouth Virus • Is a risk Australian sheep producers need to be constantly aware of

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