BLUETONGUE

ABOUT ELA

* Bluetongue virus serotype 6 in Europe in 2008—Emergence and disappearance of an unexpected non-virulent BTV

Piet A. van Rijn et all

Bluetongue viruses (BTVs) could invade N-W Europe similar to BTV serotype 8 (BTV8/net06), since the source and route of introduction of this virus has not been solved. Therefore, the Dutch survey for Bluetongue by PCR testing was extended by further analysis of PCR positives to identify the involved BTV. In late August 2008, BTV was reported with 12 nucleotide differences in the S10 amplicon (S10 genotyping). This virus was identified as serotype 6, here named BTV6/net08. Promptly, serotype specific realtime PCR tests were developed for serotypes 1, 6, and 8 (S2 genotyping).

 

* Rescue of Recent Virulent and Avirulent Field Strains of Bluetongue Virus by Reverse Genetics

Rene G. P. van Gennip et all

Since 1998, Bluetongue virus (BTV)-serotypes 1, 2, 4, 9, and 16 have invaded European countries around the Mediterranean Basin. In 2006, a huge BT-outbreak started after incursion of BTV-serotype 8 (BTV8) in North-Western Europe. More recently, BTV6 and BTV11 were reported in North-Western Europe in 2008. These latter strains are closely related to live-attenuated vaccine, whereas BTV8 is virulent and can induce severe disease in ruminants, including cattle. In addition, Toggenburg orbivirus (TOV) was detected in 2008 in Swiss goats, which was recognized as a new serotype of BTV (BTV25). The (re)emergency of known and unknown BTV-serotypes needs a rapid response to supply effective vaccines, and research to study this phenomenon. Recently, orbivirus research achieved an important breakthrough by the establishment of reverse genetics for BTV1.

 

* Clinical signs of bluetongue virus serotype 8 infection in sheep and goats

Backx et all

The confirmation of bluetongue virus serotype 8 (BTV-8) in the Netherlands on August 17, 2006 marked the onset of the first outbreak of bluetongue in north-west Europe. BTV (Orbivirus, Reoviridae) is a vectorborne, double-stranded RNA virus with 24 known serotypes, which causes a noncontagious infectious disease in ruminants. The incursion of BTV-8 into Europe was preceded by epizootics of BTV serotypes 1, 2, 4, 9 and 16 in southern Europe since 1998 (Mellor and Wittmann 2002).

 

* Overview of the bluetongue situation in Europe with emphasis on Culicoides vectors.

Rudy Meiswinkel CIDC, Lelystad, The Netherlands

Bluetongue (represented by serotype 8) appeared in northern Europe in August 2006. Subsequently, it spread across five Member States (MSs) and by December had affected an area of approximately 170 000 km2. Both cattle and sheep showed clinical signs and at least two species of Culicoides i.e. C. obsoletus and C. dewulfi were shown to be involved in its transmission. All affected MSs initiated national entomological surveillance programmes with the result that Culicoides are now monitored widely using mainly Onderstepoort-type blacklight traps. The most significant findings made over the past year are summarised and discussed with emphasis on The Netherlands, where 20 farms are sampled.

 

* The taxonomy of Culicoides vector complexes – unfinished business

R.Meiswinkel et al

The thirty species of Culicoides biting midges that play a greater or lesser role in the transmission of bluetongue (BT) disease in the pantropical regions of the world are listed. Where known, each species is assigned to its correct subgenus and species complex. In the Mediterranean region there are four species of Culicoides involved in the transmission of BT and belong in the subgenera Avaritia Fox, 1955 (three species) and Culicoides Latreille, 1809 (one species). Using both morphological and molecular second internal transcribed spacer (ITS2) sequence data, the authors reappraise the taxonomy of these four species and their congeners. A total of 56 populations of Culicoides collected from across Italy and representing 17 species (18 including the outgroup taxon C. imicola Kieffer, 1913) were analysed.

 

* Potential new Culicoides vector of bluetongue virus in northern Europe

R.Meiswinkel, Piet van Rijn, P.Leijs, M.Goffredo

BLUETONGUE is an orbiviral disease that affects domesticated ruminant livestock, especially sheep and cattle (Erasmus 1990, MacLachlan 1994). The disease occurs almost worldwide (Tabachnick 2004) and is transmitted by approximately 30 species of biting midges of the genus Culicoides.

 

* Vaccination against Bluetongue

Ivo Claassen

Symposium on Bluetongue virus sertype 8

 

* Infection of the vectors and bluetongue epidemiology in Europe

P.S.Mellor

The author describes some of the factors controlling the infection and transmission of bluetongue (BT) virus (BTV) by vector species of Culicoides. Also outlined are certain important features of the recent BT epizootic in the editerranean Basin, concentrating on those aspects involving vector transmission and overwintering of the virus. The regions affected by the outbreaks and the BTVserotypes involved are set out, the distribution of the major vector, C. imicola is described and the impact of novel vector species of Culicoides and a possible overwintering mechanism for the virus in Europe, are discussed.

 

* Bluetongue trade issues – an Australian perspective

G.R. Oliver

Although bluetongue (BT) causes large numbers of sheep mortalities in some parts of the world, the main economic global impact is due to restricted trade. Australia supports a risk-based approach using current scientific knowledge to determine animal health requirements for international trade. It is important that import health conditions for bluetongue virus (BTV) are based on science and are consistent with international guidelines. The Sanitary and Phytosanitary (SPS) Agreement of the World Trade Organization (WTO) specifies basic rights and obligations of importing and exporting member countries. The Terrestrial animal health code of the Office International des Épizooties (OIE) provides specific guidelines for BTV and general guidelines for many trade-related matters, including surveillance and zoning. The combined effect of relevant WTO-related measures and the OIE guidelines is to both encourage and require countries to apply import health requirements that are based on sound science and which afford justifiable protection without being unnecessarily trade restrictive.

 

* Epidemiological analysis of the 2006 bluetongue virus serotype 8 epidemic in north-western EuropeRole of human interventions

E. Meroc et al

The introduction, establishment, and spread of animal diseases can be heavily influenced by human interventions and therefore the role of human interventions needs to be included in an epidemiological outbreak analysis. Movement of infected ruminants or non-susceptible mammals carrying infected Culicoides can cause the introduction of bluetongue virus (BTV) and can affect its subsequent spread in a new area. BTV introduction can also result from trade in infected live animal products such as semen, ova or embryos. Thus, information on animal movements or transfer of live animal products which occurred during the onset and the course of the epidemic is of relevance to try to identify conditions for the introduction and spread of this virus.

 

* Genetically engineered multi-component virus-like particles as veterinary vaccines

L. D. Pearson and Polly Roy

Multiprotein structures can be constructed to mimic virus particles. These engineered particles lack genetic material and are not infectious but they can elicit protective immune responses in animals against challenges with infectious viruses.

 

* Eerste bluetongue-uitbraak bij geiten in Nederland: beschrijving van de klinische verschijnselen en differentieeldiagnose

D.Dercksen et al

Voor de eerste keer in Nederland en Noordwest-Europa is bij geiten bluetongue aangetoond. Bluetongue is een jaar geleden, op 17 augustus 2006, voor het eerst in Nederland aangetoond bij schapen en iets later bij runderen. De klinische verschijnselen, diagnostiek en differentieeldiagnose van bluetongue op het eerste besmette geitenbedrijf worden in dit artikel beschreven.

 

* BLUETONGUE IN ITALY: RISK ANALYSIS ON THE INTRODUCTION INTO FREE TERRITORIES OFVAC-CINATED ANIMALS FROM RESTRICTED ZONES.

Centri di Referenza Nazionali

During years from 2000 and 2002, Italy experienced the largest bluetongue (BT) epidemics in Europe. During 2000-2001 BT epidemic (from August 2000 to May 14th 2001) the disease involved 3 Italian Regions: Sardinia, Sicily and Calabria and has been diagnosed in 6,869 flocks. The final morbidity rate in infected flocks was 18.2% and the mortality rate was 3.3%. A total number of about 275,000 sheep and goats has been lost due to both BT mortality and slaughter of sick animals During 2001-2002 BT epidemic (from May 15th to April 14th 2002) the disease involved 8 Italian Regions (Sardinia, Sicily, Calabria, Basilicata, Campania, Apulia, Latium and Tuscany), with 6,807 diseased flocks. The final morbidity rate was 17.8% and the mortality rate was 5.2%. A total number of about 250,000 sheep and goats has been lost due to both BT mortality and slaughter of sick animals. At present (2002-2003 BT epidemic; from April 15th 2002), the disease has been diagnosed in 8 Regions (Basilicata, Calabria, Campania, Latium, Molise, Apulia, Sardinia and Sicily), with 402 diseased flocks. Provisory data show a 8.2% and a 6.0% morbidity and mortality rate, respectively. A total number of 2,759 sheep and goats has been lost due to both BT mortality and slaughter of sick animals.

 

* Bluetongue vectors in the Netherlands.

Willem Takken

 

* Studies on overwintering of bluetongue viruses in insects

David M. White et al

Bluetongue viruses (BTVs) are economically important arboviruses that affect sheep and cattle. The overwintering mechanism of BTVs in temperate climates has eluded researchers for many years. Many arboviruses overwinter in their invertebrate vectors. To test the hypothesis that BTVs overwinter in their vertically infected insect vectors, Culicoides sonorensis larvae were collected from long-term study sites in northern Colorado, USA, and assayed for the presence of BTV RNA by nested RT-PCR.

 

* Studies on bluetongue disease in the People’s Republic of China

N. Zhang et al

Bluetongue (BT) is an important infectious, non-contagious, insect-borne viral disease of ruminants, and is classified as a ‘List A’ disease in the OIE Terrestrial animal health code. Since the first discovery and diagnosis of this disease in the Shizong County of Yunnan Province in 1979, the authors have developed systematic studies of the epidemiology, experimental epidemiology, aetiology, pathology, viral molecular characteristics (nucleic acid), diagnostic techniques, virus identification (grouping and typing) methods, vaccines and immunisation methods of BT in the People’s Republic of China.

 

* Recombinant Virus Vaccine for Bluetongue Disease in Sheep

P. Roy et al

Bluetongue virus proteins derived from baculovirus expression vectors have been administered in different combinations to sheep, a vertebrate host susceptible to bluetongue virus, and the neutralizing antibody responses were measured. Vaccinated sheep were subsequently challenged, and the indices of clinical reaction were calculated. The results indicated that the outer capsid protein VP2 alone in doses of >50 ,ug per sheep elicited protection. A dose of ca. 50 ,ug of VP2 protected some but not all sheep. However, when used in combination with ca. 20 ,ug of the other outer capsid protein, VP5, 50-F,g quantities of VP2 not only protected all the vaccinated sheep but also elicited a higher neutralizing-antibody response. The addition of viral core proteins VP1, VP3, VP6, and VP7, the nonstructural proteins NS1, NS2, and NS3, and the outer capsid proteins VP2 and VP5 did not enhance this neutralizing-antibody response.