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