Bluetongue

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Bluetongue
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Background to the disease
Current situation in the UK
Clinical signs in sheep and cattle
Methods of control
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A VIRAL DISEASE24 serotypes
No effective treatment
Affects ruminants and camelids
DOES NOT AFFECT MAN or other animals
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A VECTOR-BORNE DISEASE
Not contagious indirect transmission
Increase in vector borne diseases worldwide
since 1970s
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Vector borne diseases
World Erlichiosis (heartwater) Sub-saharan
Africa Trypanosomiasis Sub-saharan
Africa Theileriosis Middle East Anaplasmosis
Southern Europe
UK Babesia sp - Babesiasis - ticks Rickettsia -
Tick borne fever - ticks Louping ill virus -
ticks Bluetongue virus culicoides midge
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Transmission
Midge bites viraemic animal (2 infection
rate) Virus passes through the gut wall of the
midge and replicates in midge salivary
glandsMidge bites naive animal and injects
saliva (100 infection rate) Virus replicates in
animal cellsAnimal becomes viraemic
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Cattle viraemic for 50-60 daysSheep viraemic for
10-20 days
Transmission
Virus multiplies in midge more quickly in hot
weather Will not multiply when temp lt 150C
So how does the virus survive over-winter in
northern latitudes when the midge is inactive?
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Possible multiple mechanisms In adult
midges In midge larvae In adult
animals In animals passing from dam
to foetus
Overwintering
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Bluetongue virus is spreading
Global warming
Trade - greater animal movements? Virus
changing? New vectors
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Bluetongue distribution before 1998
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Bluetongue distribution in 2007
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Spread within Europe - 2003
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2
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Spread within Europe - 2004
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Spread within Europe - 2006
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How did BTV8 arrive in Northern Europe?
Imported carrier ruminants?
Infected midges?
Wind borne? On other animals? On plants?
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How did BTV8 arrive in the UK?
Imported carrier ruminants?
Infected midges?
Wind borne
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Wind Plume From Mainland Europe
Initial midge hatch starts here on the evening of
the 4th August 2007
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Wind Plume From Mainland Europe
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Wind Plume From Mainland Europe
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Wind Plume From Mainland Europe
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Wind Plume From Mainland Europe
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Wind Plume From Mainland Europe
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Wind Plume From Mainland Europe
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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
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4 August winds blow infected midges
from Netherlands to East Anglia22 Sept
disease confirmed in Ipswich30 Nov - 65
premises confirmed 23 more premises in Jan and
Feb 08 detected through pre-movement testing
Situation in UK
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22nd February
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29th February No more pre-movement testing
after March 15th Zones fixed until next
outbreak
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Clinical Signs
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Short lived fever dull, off food, reluctant to
riseVascular disease attacks blood
vesselsOedema - swollen face, ears,
legsSalivation ulceration of the mouth and
nose, droolingRedness of gums, eyes, coronary
bands of feetRespiratory distress difficulty
breathingWeight loss, wool slip
Clinical Signs
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Ulceration of tongue
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Ulceration of lips and dental pad
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Locomotion

• Isolated from the flock
• Unwilling to stand
• Stiff or lame hunched appearance
• Coronitis, laminitis, arthritis
• Loss of condition (inability to move / eat)

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Morbidity 27 Mortality 11
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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

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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

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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

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Supportive therapyWarmth and shelterAntibiotic
s, fluids and anti-inflammatoriesDiet
Treatment
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Low morbidity only 2-3 cases per farmBlood
test 16 cattle ve - 5 sheep
veBUT 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
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Reduce/eliminate vectors Prevent sheep and
vectors interactingRestrict animal movements
Vaccination
Control
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Total elimination of midges impossible
Control the vector
Reduce numbers Reduce stagnant water Larvicidal
treatments Insecticides
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Insecticidal sprays Sheep dips Dont move
animals at dawn and dusk Dont stop vehicles
overnight Darken the inside of vehicles
Prevent midge biting sheep
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Restrict animal movements
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Modified live vaccines banned in
EUInactivated vaccines permitted in EU 24
immunologically distinct serotypesNo
cross-protection between serotypesMany strains
within serotypes
Vaccination
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BTV 8Intervet - virus from 2006 infected
cowKilled vaccineSingle dose for sheep,
double dose for cattle1ml dose in 20 and 50 ml
bottlesAnnual booster
Vaccination
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Compulsory?Voluntary?Need high take up for
control 80
Vaccination
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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 farmerVet
certification needed for exportRecord all use
in medicine books
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Questions?