The emergence, persistence and evolution of bluetongue viruses in Europe since 1998 Peter Mertens. School of Veterinary Medicine and Science

Transcription

1 The emergence, persistence and evolution of bluetongue viruses in Europe since 1998 Peter Mertens

2 Bluetongue virus: History pre 1998 First described in 18th century: confined to Africa 1924 Cyprus, 70% mortality Palestine and Turkey 1948 USA 1951 Israel and Asia 1956 BTV-10 Eastern Mediterranean (Morocco, Spain, Portugal ) 75% mortality in sheep, 17,900 killed in 4 months BTV-4 Cyprus BTV-4, Greece. European outbreaks were infrequent, short lived and involved only a single BTV serotype on each occasion.

3 BTV History: after multiple annual incursions started into Southern Europe Multiple exotic serotypes arriving in Southern USA New serotypes (BTV-2, BTV-7 in Australia) Western vaccine-strains (BTV-2, BTV-10) in India (disease in native breeds ~25% sheep fatality rates ) 2006 BTV-8 in northern Europe (~25% sheep mortality) Novel serotypes - detection of BTV-25, 26, 27, BTV-4 arrives and spreads in eastern Europe BTV-8 reappears in central France (but low virulence)

4 C. obsoletus Culicoides vector species from Europe, Africa and the USA C. sonorensis C. imicola C. impunctatus (pulicaris complex)

5 Bluetongue: clinical signs

6 Haemorrhages in the dermis of a BTV-8 infected sheep, at 8 d.p.i (peak of viraemia)

7 The first recorded outbreak of Bluetongue in Northern- Europe started in the Netherlands during 2006 efore spreading across the rest of Europe Mouth ulcers Conjunctivitis Coronitis Cyanotic appearance of tongue Conjunctivitis FLI

8 4-week old calf with behavioural & locomotory problems. Brain with cerebral hemispheres replaced by a fluid filled sac. (Wouda et al 2008)

9 Bluetongue: Virus structure

10 Organisation of the BTV capsid and genomic dsrna Virus particle Core partic le Subcore particle Ten segmente d dsrna genome

11 The outer surface of the BTV virus particle VP and VP5 - Encoded by segments 2 and 6 (Cryo-EM and x-ray crystallography reconstruction) 60, VP2 trimers, encoded by Seg VP5 trimers, encoded by Seg-6

12 The emergence of Bluetongue In Europe Since 1998 Why is this happening now?

13 Introductions of different BTV strains into Europe and North Africa 1998 to end of 2007 BTV BTV BTV-1 BTV BTV-2 BTV-16 BTV-1 BTV-4 & BTV

14 Reassortment of BTV genes in Europe BTV-4, Med to Austria BTV-8 outbreak from Northern Europe School of 2 Veterinary Medicine and Science CAR1982/0 1 BTV-1 outbreak Mediterranean to north France From: Widespread reassortment shapes the evolution and epidemiology of bluetongue virus Nomikou, et al, PLoS Pathog 11(8): e doi: /journal.ppat

15 The effect of temperature on incubation in the insect : extrinsic incubation period (Purse et al., 2005)

16 Incorporation of radio labelled substrates into RNA BTV -1 polymerase activity Temperature

17 Recent climate warming and Bluetongue outbreaks in Europe 11 BTV serotypes have been detected in Europe Since 1998

18 The recent emergence / detection of novel BTV serotypes

19 Comparison of Seg-2 sequences for 27 BTV types 19RSArrrr/19-AJ RSArrrr/07-AJ RSArrrr/18-AJ RSArrrr/08-AJ RSArrrr/05-AJ RSArrrr/23-AJ RSArrrr/09-AJ BTV-1 GRE2001/01 AJ RSArrrr/01-AJ RSArrrr/02-AJ BTV-2-Taiwan- AY RSArrrr/14-AJ RSArrrr/06-AJ W E E BTV-25 TOV-EU BTV-27 iso 379-KM BTV-26 KUW2010/02-HM RSArrrr/24-AJ RSArrrr/10-AJ RSArrrr/21-AJ RSArrrr/03-AJ RSArrrr/16-AJ RSArrrr/13-AJ RSArrrr/11-AJ RSArrrr/17-AJ RSArrrr/20-AJ RSArrrr/04-AJ RSArrrr/12-AJ RSArrrr/15-AJ RSArrrr/22-AJ

20 Institute of Diagnostic Virology BTV-Mongolia2 BTV-Mongolia1 Phylogenetic tree 400 bp of Seg-2 (VP2) Identities between BTV from Mongolia is 65-72%

21 BTV Segment 3 phylogenetics Recent serotypes: BTV-25 and above Eastern topotype: mainly Asia, Oceania, Europe Novel serotypes also Novel topotype(s)? Major Eastern topotype Western topotype: mainly Americas, Africa, Europe Major Western topotype

22 BTV-26 BTV-26 identified in 2010 in sheep from Kuwait caused only very mild disease in sheep. replicates and persists in goats but no clinical signs. detected in urine. contact transmission was detected between goats, in the absence in insects. BUT did not infect adult Culicoides or Culicoides cell line (KC cells).

23 BTV-26 transmission study in goats: v v v v v v Samples of serum, EDTA blood and nasal/ocular swabs were taken throughout the study 3 infected goats 3 in contact controls 4 barrier control goats 1ml Subcutaneous inoculation BTV-26 KUW2010/09 BHK TCID 50 /ml

24 Generation of BTV-1/BTV-26 mono-reassortants by reverse genetics BT V- 1 BT V- 26 Panel of generated BTV-1/BTV-26 mono-reassortants Pullinger et al., (2016). In PLoS ONE. doi: /journal.pone

25 Replication of BTV-1 and BTV-26 reassortants in BSR cells Seg-1 Seg-2, 6, 7 Seg-3 Seg-4 Seg-5 Seg-6 Seg-7 Seg-8 Seg-9 Seg-10 MOI = 0.04, Values are means ± SEM of 3 experiments, with 2 determinations each

26 Replication of BTV-1 and BTV-26 reassortants in KC cells

27 BTV-26 proteins restricting replication in Culicoides cell cultures (KC cells)

28 Binding of purified BTV virus particle to BSR and KC cells Uninfected BSR cells BTV-26 BSR cells BTV-26 KC cells Binding of purified BTV-1 or BTV-26 virus particles to BSR or KC cells after 1hour at 4 o C. BTV-1 KC cells

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30 Summary concerning the BTV outbreaks in Northern Europe BTV-8 (same lineage) re-emerged in France in 2015 and the outbreak still appears to be spreading. How did it persist through 5 free years? Why so few clinical cases, this time? Has the virus or host population changed? BTV-4 also spread north from southern Greece, as far as Austria, Slovakia, Romania and Hungary. The at risk /endemic zone for BTV may therefore be spread further north from the Mediterranean region. The increased proximity may represent an elevated risk of reintroduction to northern Europe. Unlike the 2007 outbreak vaccine is available to farmers. The risk of BTV incursion into UK population is currently assessed as LOW. It is likely that new BTV strains (and other arboviruses) will continue to spread into Europe.

31 Acknowledgements Support from: BBSRC; Defra; Wellcome Trust; the European Commission; OIE, DBT-India; Embrapa Brazil. Massimo Palmarini, Roman Biek and colleagues at the CVR in Glasgow Stephan Zientara, Houssam Attoui, Emmanuel Breard, and colleagues ANSES / INRA, Maisons Alfort, Paris. Bernd Hoffmann, FLI Rhiems Germany Sushila Maan< Narender Maan, LUVAS University India Carrol de Mattos, Zelia Lobato, Maria Guedes, Julio Rosa, Erica Costa : UFMG Belo Horizonte, Brazil Carrie Batten Karin Darpel, TPI Prirbight UK Peter Kirkland, EMAI, New South Wales, Australia