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.
Epidemiological
analysis of the 2006 bluetongue virus serotype 8 epidemic in north-western
EuropeRole of environmental factors – wind analysis G.Hendrickx et al Whilst micro-organisms causing disease are increasingly being moved
around the world by rising rates of trade and travel, the dispersal of insect
vectors also has been implicated in the introduction of vector-borne pathogens
into new areas. However, the impact of this potential route of introduction
must not be underestimated. Ritchie and Rochester (2001) showed for example
that Japanese Encephalitis was introduced into Australia by wind-blown Culex
spp., while Baker et al (1990) demonstrated the reinvasion of cleared land
by wind-borne Simulium spp. spread by monsoonalwinds during the rainy season
in West Africa. Therefore, analysing the process of arrival, establishment
and consequent spread of these vectors is very important.
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.
Probability of introduction
of exotic strains of bluetongue virus into the US and into California through
importation of infected cattle. Bruce
R. Hoara et al Strategies designed to minimize the probability of bluetongue virus
(BTV) introduction to new areas should be based on a quantitative assessment
of the probability of actually establishing the virus once it is introduced.
The risk of introducing a new strain of bluetongue virus into a region depends
on the number of viremic animals that enter and the competency of local
vectors to transmit the virus. We used Monte Carlo simulation to model the
probability of introducing BTV into California, USA, and the US through
importation of cattle.
Scientific Opinion
of the Scientific Panel on Animal Health and Welfare on request from the
European Commission on bluetongue vectors and vaccines. EFSA The current distribution of bluetongue (BT) in Europe deserves special
consideration in regard to the spread and epidemiology of BT virus (BTV)
into new regions, the surveillance and monitoring activities of MSs, the
clinical and laboratory diagnosis of BT, a scientific approach being adopted
in the use of vaccines against BTV, and possible control of the Culicoides
vectors implicated in the spread of all BTVs. BTV serotype 8 affected five
countries in Northern Europe whereas other serotypes (BTV-1, -2, -4, -9
and -16) had been responsible for the recent and multiple outbreaks of BT
in parts of Southern Europe.
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.
