Bluetongue

Background to the disease

Current situation in the UK

Clinical signs in sheep and cattle

Methods of control

A VIRAL DISEASE24 serotypes

Affects ruminants and camelids

DOES NOT AFFECT MAN or other animals

No effective treatment

A VECTOR-BORNE DISEASE

Not contagious – indirect transmission

Increase in vector borne diseases worldwide since 1970s

Vector borne diseases

UKBabesia sp - Babesiasis - ticksRickettsia - Tick borne fever - ticksLouping ill virus - ticksBluetongue virus – culicoides midge

WorldErlichiosis (heartwater) – Sub-saharan AfricaTrypanosomiasis – Sub-saharan AfricaTheileriosis – Middle EastAnaplasmosis – Southern Europe

Transmission

Midge bites viraemic animal (2% infection rate)

Virus passes through the gut wall of the midge and replicates in midge salivary glands

Midge bites naive animal and injects saliva (100% infection rate)

Virus replicates in animal cellsAnimal becomes viraemic

Transmission

Cattle viraemic for 50-60 daysSheep viraemic for 10-20 days

So how does the virus survive over-winter in northern latitudes when the

midge is inactive?

Virus multiplies in midge more quickly in hot weather Will not multiply when temp < 150C

Possible multiple mechanisms

In adult midges

In midge larvae

In adult animals

In animals passingfrom dam to foetus

Overwintering

Bluetongue virus is spreading

Trade - greater animal movements?Virus changing?

New vectors

Global warming

Bluetongue distribution before 1998

Bluetongue distribution in 2007

42

4

Spread within Europe - 2003

4

16

4

2

4

9 + 16

Spread within Europe - 2004

4

4 44

16

4

22

4

1

11 1

9 + 16

Spread within Europe - 2006

444

4

8

1624

How did BTV8 arrive in Northern Europe?

Imported carrier ruminants?

Infected midges?

Wind borne?On other animals?On plants?

How did BTV8 arrive in the UK?

Imported carrier ruminants?

Infected midges?

Wind borne

Wind Plume From Mainland Europe

Initial midge hatch starts here on the evening of the 4th August 2007

Wind Plume From Mainland Europe

Wind Plume From Mainland Europe

Wind Plume From Mainland Europe

Wind Plume From Mainland Europe

Wind Plume From Mainland Europe

Wind Plume From Mainland Europe

Wind Plume From Mainland Europe

The morning of the 5th August conditions change and midges drop out of the plume to land in Norfolk and Suffolk

4 August – winds blow infected midges from Netherlands to East Anglia

22 Sept – disease confirmed in Ipswich

30 Nov - 65 premises confirmed

23 more premises in Jan and Feb 08 detected through pre-movement testing

Situation in UK

22nd February

29th February

No more pre-movement testing after March 15th

Zones fixed until next outbreak

Clinical Signs

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Short lived fever – dull, off food, reluctant to rise

Vascular disease – attacks blood vessels

Oedema - swollen face, ears, legs

Salivation – ulceration of the mouth and nose, drooling

Redness of gums, eyes, coronary bands of feet

Respiratory distress – difficulty breathing

Weight loss, wool slip

Clinical Signs

Ulceration of tongue

Ulceration of lips and dental pad

Locomotion

• Isolated from the flock

• Unwilling to stand

• Stiff or lame – hunched appearance

• Coronitis, laminitis, arthritis

• Loss of condition (inability to move / eat)

Morbidity 27%Mortality 11%

Recovered animals

Loss of body condition – 6 weeks to recover

Milk yield drop

Poor lamb growth, wool slip

Infertility

Ewe: Abortion (5-6%),

Embryonic deaths = lower lambing

Ram: Poor sperm quality, low pregnancy rate

May be sterile for up to 1 year

Clinical Signs in Cattle

• Wide Variation in Clinical Signs• Low morbidity (+/-10%) in affected herds with only one or two

animals showing clear clinical signs.

• Low mortality (2%)

• Initial signs:

• -Slow, stiff gate, depressed

• -Decrease in appetite

• -Drop in milk

• -Reddening of the whites of the eyes, inside of the nose and nasal discharge

The Following Days

• Erosions of the muzzle

• Sunburn-like lesions on the white skin of the nose and teats

• Purulent nasal discharge, frothy drool

• Erosive lesions on roof and bottom of the mouth

• Sub endothelial haemorrhages

• Swollen feet, inflammation of the coronary band

• Oedema of the lower limb

Supportive therapy

Warmth and shelter

Antibiotics, fluids and anti-inflammatories

Diet

Treatment

Low morbidity – only 2-3 cases per farmBlood test – 16% cattle +ve

- 5% sheep +ve

BUT

Experience on continent is that in the 2nd year there are more cases and greater severity

The same farms are often re-infected.

Experience in UK to date

Reduce/eliminate vectors

Prevent sheep and vectors interacting

Restrict animal movements

Vaccination

Control

Control the vector

Total elimination of midges impossible

Reduce numbers

Reduce stagnant water

Larvicidal treatments

Insecticides

Insecticidal sprays

Sheep dips

Don’t move animals at dawn and dusk

Don’t stop vehicles overnight

Darken the inside of vehicles

Prevent midge biting sheep

Restrict animal movements

Modified live vaccines – banned in EU

Inactivated vaccines – permitted in EU

24 immunologically distinct serotypes

No cross-protection between serotypes

Many strains within serotypes

Vaccination

Vaccination

BTV 8

Intervet - virus from 2006 infected cow

Killed vaccine

Single dose for sheep, double dose for cattle

1ml dose in 20 and 50 ml bottles

Annual booster

Vaccination

Compulsory?

Voluntary?

Need high take up for control – 80%

Vaccination

2 million doses due for release in May 2008

For use in the PZ areas only

Purchased through vet, but can be administered by farmer

Vet certification needed for export

Record all use in medicine books

Questions?