Bluetongue

Background to the disease Current situation in the UK Clinical signs in sheep and cattle Methods of control

A VIRAL DISEASE 24 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 UK Babesia sp - Babesiasis - ticks Rickettsia - Tick borne fever - ticks Louping ill virus - ticks Bluetongue virus – culicoides midge World Erlichiosis (heartwater) – Sub-saharan Africa Trypanosomiasis – Sub-saharan Africa Theileriosis – Middle East Anaplasmosis – 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 cells Animal becomes viraemic

Transmission Cattle viraemic for days Sheep viraemic for 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 < 15 0 C

Possible multiple mechanisms In adult midges In midge larvae In adult animals In animals passing from 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

4 2 4 Spread within Europe

Spread within Europe

Spread within Europe

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 4 th August 2007

Wind Plume From Mainland Europe

The morning of the 5 th 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

22 nd February

29 th February No more pre-movement testing after March 15 th Zones fixed until next outbreak

Clinical Signs

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 farm Blood test – 16% cattle +ve - 5% sheep +ve BUT Experience on continent is that in the 2 nd 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

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?