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)
Mortality 0% in accustomed sheep to 90% in susceptible sheep
Are at least 16 strains of BTV
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
BTV Movement into Europe 2006-8
BTV Movement into Europe 2008
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????
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?
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
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
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
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???
Foot and Mouth Disease
Foot and Mouth Disease in Australia
Until now - Control by Eradication or Stamp Out
But after UK 2001 Governments wary of adverse publicity
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
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
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
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
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
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!
Foot and Mouth Disease(a tale of two outbreaks)
UK Feb 2001 outbreak was well publicised Uruguay May 2001 outbreak almost
unheard of UK Uruguay
Area 244,000 km2 180,000 km2
No. Cattle 10,600,000 10,600,000
No. Pigs 5,800,000 270,000
No. Sheep 36,700,000 12,000,000
Foot and Mouth Disease(a tale of two outbreaks)
Final outcome after eradication
UK (Stamp Out)
Uruguay (Vaccination)
Resumption of Trade
49 weeks 104 weeks
Animals killed 6,000,000 7,000Total Cost of Eradication
$10 billion $244 million
Note: Only cattle vaccinated in Uruguay. 24 million doses of vaccine used in Uruguay
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