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 n n 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
Blue Tongue Virus n n n Has been in NT sentinel sheep since 1970 s? (maybe 1956) Reservoir of infection in Africa and M. East Moved into Northern Europe in 2006 -8
BTV Movement into Europe 2006 -8
BTV Movement into Europe 2008
Concerns n Spread into N Europe n n n 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 n Possibly due to transplacental hibernation? ?
What about Australia? n Insects eg Culicoides float into Australia periodically from Timor and Papua New Guinea n n n 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?
Is this a risk for Australia? n Blood from Qld passaged in a sheep at AHL, Geelong 2010 n n 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 n All became severely affected and were euthanased Source: nunetherlands. com
Should we be concerned ? n Culicoides spp n n 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
What can we do? n Control possibilities n n 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
Management of BTV n Vaccination n UK n n n South Africa n n killed vaccine $2 per head yearly Live attenuated vaccine Once in a lifetime But vaccine can be infective Insect Control n n House sheep at night? Ivermectin? ? ?
Foot and Mouth Disease
Foot and Mouth Disease in Australia n n Until now - Control by Eradication or Stamp Out But after UK 2001 Governments wary of adverse publicity
Foot and Mouth Disease n n n Australia now leaning towards Vaccination International symposium in Melb in May 2010 International workshop on FMD outbreak n n n How would vaccine be used? When? What issues may arise? Source: MSD animal health
Foot and Mouth Disease n Vaccination n n 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
Foot and Mouth Disease n Diagnosis n n n Blood tests look for antibodies = evidence of infection But both natural infection and vaccination cause antibodies How can we tell vaccinated from infected animals? n DIVA test = Differentiate between Infected and Vaccinated Animals
Foot and Mouth Disease n Diagnosis by DIVA tests n n 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
Foot and Mouth Disease n Trade Issues (OIE) n Trade prohibited for 3 months after last case n n n Trade prohibited for 3 months after last case or vaccinated animals slaughtered n n Extensive surveillance needed to prove this Only once has this been achieved so usually much longer Extensive surveillance needed to prove this Trade prohibited for 6 months after last case OR vaccination withdrawal (animals allowed to live) n If using this method need DIVA testing and surveillance
Foot and Mouth Disease n Trade Issues n n Outbreak could be expected to last up to 2 years before trade can resume What do we do with the slaughtered animals? n n n Can’t export and we can’t eat that many Effect on stock values? Will be a real problem!
Foot and Mouth Disease (a tale of two outbreaks) n n UK Feb 2001 outbreak was well publicised Uruguay May 2001 outbreak almost unheard of UK Uruguay Area 244, 000 km 2 180, 000 km 2 No. Cattle 10, 600, 000 No. Pigs 5, 800, 000 270, 000 No. Sheep 36, 700, 000 12, 000
Foot and Mouth Disease (a tale of two outbreaks) n Final outcome after eradication UK Uruguay (Stamp Out) (Vaccination) Resumption of Trade 49 weeks 104 weeks Animals killed 6, 000 7, 000 Total Cost of Eradication $10 billion $244 million Note: Only cattle vaccinated in Uruguay. 24 million doses of vaccine used in Uruguay
Conclusions n Blue Tongue Virus n n May be more of a threat to Southern sheep areas than previously thought Foot and Mouth Virus n Is a risk Australian sheep producers need to be constantly aware of
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