The epidemiology and diagnosis of bluetongue with particular reference to Corsica

Abortive diseases and their various associated risk factors in small ruminants in Algeria: a systematic review

Abortive infections are a major health challenge affecting productive and reproductive performance of sheep and goats. However, there is no comprehensive summary on the occurrence and distribution of these infections in Algeria. This systematic review provides a comprehensive summary on the prevalence of different abortive diseases and assesses potential risk factors in small ruminants in Algeria. Five databases were used to search epidemiological data on the prevalence of different abortive diseases (bacterial, parasitic, and viral). Data were collected from 25 papers published between 2003 and 2020. The total mean sample size was 53,080 small ruminants. The majority of the diseases/infections were diagnosed by serological and molecular tests. The overall prevalence of brucellosis was 0.39% in sheep and 5.31% in goats. Chlamydia and Q fever were observed in 32.72% and 20.62% of small ruminants, respectively. The prevalence of peste des petits ruminants was 15.76% and the overall prevalence of bluetongue in sheep and goats was, respectively, 13.41% and 44.50%. Border disease and bovine viral diarrhea were detected in 22.68% and 1.01% of sheep examined, respectively. Toxoplasma gondii infection prevalence among sheep and goats was 21.43% and 32.31% respectively. This study is a comprehensive epidemiological analysis of abortion diseases in small ruminants in Algeria and will therefore be a useful tool for researchers. Larger and more robust prevalence studies are needed to adequately support risk assessment and management of animal and public health threats.

Bluetongue Virus in France: An Illustration of the European and Mediterranean Context since the 2000s

Bluetongue (BT) is a non-contagious animal disease transmitted by midges of the Culicoides genus. The etiological agent is the BT virus (BTV) that induces a variety of clinical signs in wild or domestic ruminants. BT is included in the notifiable diseases list of the World Organization for Animal Health (OIE) due to its health impact on domestic ruminants. A total of 27 BTV serotypes have been described and additional serotypes have recently been identified. Since the 2000s, the distribution of BTV has changed in Europe and in the Mediterranean Basin, with continuous BTV incursions involving various BTV serotypes and strains. These BTV strains, depending on their origin, have emerged and spread through various routes in the Mediterranean Basin and/or in Europe. Consequently, control measures have been put in place in France to eradicate the virus or circumscribe its spread. These measures mainly consist of assessing virus movements and the vaccination of domestic ruminants. Many vaccination campaigns were first carried out in Europe using attenuated vaccines and, in a second period, using exclusively inactivated vaccines. This review focuses on the history of the various BTV strain incursions in France since the 2000s, describing strain characteristics, their origins, and the different routes of spread in Europe and/or in the Mediterranean Basin. The control measures implemented to address this disease are also discussed. Finally, we explain the circumstances leading to the change in the BTV status of France from BTV-free in 2000 to an enzootic status since 2018.

The first report on serotyping of bluetongue virus in small ruminants of Khyber Pakhtunkhwa province, Pakistan

Bluetongue virus (BTV), a member of Orbivirus genus (family Reoviridae), is a non-contagious infection of domestic and wild ruminants. The current study was designed to detect various serotypes of BTV in small ruminants of Khyber Pakhtunkhwa (KPK) province of Pakistan, along with their effects on hemato-biochemical parameters. A total of 408 serum samples in four districts (Mansehra, Abbottabad, Swabi, and Kohat) of KPK from small ruminants were screened based on competitive ELISA (cELISA). A total of 204 (50%) samples were found positive for BTV group-specific antibodies. The seropositive samples were processed for the detection of BTV serotypes through real-time polymerase chain reaction (qPCR). Out of 204 cELISA-positive samples, 60 (29.41%) were found positive through qPCR. Three serotypes [6, 8, 9] were detected from Mansehra District and two from Kohat [2, 8] and Abbottabad [6, 8], while only one from Swabi [8]. The serotype "8" was found consistently in all the four study districts. A significant (p < 0.05) increase in the level of blood urea nitrogen (BUN) and alkaline phosphatase (ALP) was recorded in goats, whereas aspartate aminotransferase (AST) in sheep infected with BTV, compared to healthy animals. The hematological parameters showed significantly (p < 0.05) raised total leucocyte count (TLC) in both sheep and goats, whereas only hematocrit (HCT) value was increased significantly (p < 0.05) in infected sheep. This is the first report on serotyping of BTV among small ruminants in Pakistan.

Sero-epidemiology of bluetongue virus (BTV) infection in sheep and goats of Khyber Pakhtunkhwa province of Pakistan

Bluetongue virus (BTV) infection is an emerging hazard in small ruminants having socio-economic impacts on animals and associated people. The current study was aimed to estimate the sero-prevalence and associated risk factors in sheep and goat from Khyber Pakhtunkhwa (KP) province of Pakistan. Three distinct zones (northern, central and southern) with four districts (Mansehra, Abbottabad, Swabi, and Kohat) with a higher population of small ruminants were selected. A total of n = 408 sera originating from sheep (n = 212) and goats (n = 196) were randomly collected for detection of BTV group specific antibodies through competitive ELISA (c-ELISA). Univariable and multiple logistic regressions were applied to assess the potential risk factors associated with the occurrence of this disease. Results showed an overall prevalence of 50.00% (CI = 44.17-54.83) of BTV in both sheep and goats with a significant difference (p < 0.05) among different districts. The prevalence of BTV in sheep was found higher (56.60%, CI = 49.6-63.4) than goats (42.86%, CI = 35.8-50.1). The risk factors identified based on chi-square test were; 1-2 year of animals, herd size and location in sheep while, milking status, ticks infestation, location and herd size for goats (p < 0.05). On the basis of univariable analysis, 1-2 year of animals, and location for sheep while, ticks infestation and location for goats (OR > 1). Multiple logistic regressions conferred only herd size and location as potential risk factors (OR > 1) for BTV in sheep and goats. The study concluded higher prevalence of BTV in sheep than the goats, the risk factors were significantly associated with the occurrence of disease, and together ascertaining the needs to design appropriate disease management and control strategies in sheep and goats.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): bluetongue

A specific concept of strain was developed in order to classify the BTV serotypes ever reported in Europe based on their properties of animal health impact: the genotype, morbidity, mortality, speed of spread, period and geographical area of occurrence were considered as classification parameters. According to this methodology the strain groups identified were (i) the BTV strains belonging to serotypes BTV-1-24, (ii) some strains of serotypes BTV-16 and (iii) small ruminant-adapted strains belonging to serotypes BTV-25, -27, -30. Those strain groups were assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7, Article 5 on the eligibility of bluetongue to be listed, Article 9 for the categorisation according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to bluetongue. The assessment has been performed following a methodology composed of information collection, expert judgement at individual and collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. The strain group BTV (1-24) can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL, while the strain group BTV-25-30 and BTV-16 cannot. The strain group BTV-1-24 meets the criteria as in Sections 2 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (b) and (e) of Article 9(1) of the AHL. The animal species that can be considered to be listed for BTV-1-24 according to Article 8(3) are several species of Bovidae, Cervidae and Camelidae as susceptible species; domestic cattle, sheep and red deer as reservoir hosts, midges insect of genus Culicoides spp. as vector species.

Complete genome sequence of bluetongue virus serotype 4 that emerged on the French island of Corsica in December 2016

In November 2016, sheep located in the south of Corsica island exhibited clinical signs suggestive of bluetongue virus (BTV) infection. Laboratory analyses allowed to isolate and identify a BTV strain of serotype 4. The analysis of the full viral genome showed that all the 10 genomic segments were closely related to those of the BTV-4 present in Hungary in 2014 and involved in a large BT outbreak in the Balkan Peninsula. These results together with epidemiological data suggest that BTV-4 has been introduced to Corsica from Italy (Sardinia) where BTV-4 outbreaks have been reported in autumn 2016. This is the first report of the introduction in Corsica of a BTV strain previously spreading in eastern Europe.

Current and next-generation bluetongue vaccines: Requirements, strategies, and prospects for different field situations

Bluetongue virus (BTV) causes the hemorrhagic disease bluetongue (BT) in ruminants. The best way to control outbreaks is vaccination. Currently, conventionally modified-live and inactivated vaccines are commercially available, which have been successfully used to control BT, but nonetheless have their specific shortcomings. Therefore, there is a need for improved BT vaccines. The ideal BT vaccine is efficacious, safe, affordable, protective against multiple serotypes and enables the differentiation of infected from vaccinated animals. Different field situations require specific vaccine profiles. Single serotype outbreaks in former BT-free areas need rapid onset of protection against viremia of the respective serotype. In contrary, endemic multiple serotype situations require long-lasting protection against all circulating serotypes. The ideal BT vaccine for all field situations does not exist and balancing between vaccine properties is needed. Many new vaccines candidates, ranging from non-replicating subunits to replicating next-generation reverse genetics based vaccines, have been developed. Some have been tested extensively in large numbers of ruminants, whereas others were developed recently and have only been tested in vitro and in mice models. Most vaccine candidates are promising, but have their specific shortcomings and advantages. In this review, current and next-generation BT vaccines are discussed in the light of prerequisites for different field situations.

Viral emergence and consequences for reproductive performance in ruminants: two recent examples (bluetongue and Schmallenberg viruses)

Viruses can emerge unexpectedly in different regions of the world and may have negative effects on reproductive performance. This paper describes the consequences for reproductive performance that have been reported after the introduction to Europe of two emerging viruses, namely the bluetongue (BTV) and Schmallenberg (SBV) viruses. Following the extensive spread of BTV in northern Europe, large numbers of pregnant cows were infected with BTV serotype 8 (BTV-8) during the breeding season of 2007. Initial reports of some cases of abortion and hydranencephaly in cattle in late 2007 were followed by quite exhaustive investigations in the field that showed that 10%-35% of healthy calves were infected with BTV-8 before birth. Transplacental transmission and fetal abnormalities in cattle and sheep had been previously observed only with strains of the virus that were propagated in embryonated eggs and/or cell culture, such as vaccine strains or vaccine candidate strains. After the unexpected emergence of BTV-8 in northern Europe in 2006, another arbovirus, namely SBV, emerged in Europe in 2011, causing a new economically important disease in ruminants. This new virus, belonging to the Orthobunyavirus genus in the Bunyaviridae family, was first detected in Germany, in The Netherlands and in Belgium in 2011 and soon after in the UK, France, Italy, Luxembourg, Spain, Denmark and Switzerland. Adult animals show no or only mild clinical symptoms, whereas infection during a critical period of gestation can lead to abortion, stillbirth or the birth of severely malformed offspring. The impact of the disease is usually greater in sheep than in cattle. The consequences of SBV infection in domestic ruminants and more precisely the secondary effects on off-springs will be described.

Seroepidemiology of bluetongue disease in small ruminants of north-east of Iran

OBJECTIVE

To estimate the prevalence and distribution of bluetongue virus antibody in sheep and goats in 25 townships of Khorasan Razavi. Bluetongue is an infectious, non-contagious, arthropod born viral disease of ruminants and has been reported from most of the tropical and subtropical regions of the world.

METHODS

A total number of 1 034 serum samples from sheep and goats were collected and transmitted to Serological Laboratory of Veterinary Council of Khorasan Razavi. Serums were screened for the presence of group-specific bluetongue virus antibody using competitive Enzyme Linked Immuno Sorbent Assay (c-ELISA).

RESULTS

The seropositivity of sheep and goats for bluetongue was found to be 89.2%. The highest prevalence rate was seen in Taybad, Khalil-abad and Torbat-jam (100%) and the least prevalence rate was seen in Jovein (55%).

CONCLUSIONS

The results showed that the majority of animals in the north-east of Iran are infected with bluetongue virus. High correlation between abortion history and seroposivity emphasize the economical importance of bluetongue virus in the sheep herds of the region.

High seroprevalence of bluetongue virus antibodies in goats in southeast Iran

OBJECTIVE

To describe the seroprevalence rate of bluetongue virus (BTV) in goat flocks in southeast of Iran.

METHODS

The blood samples were collected randomly from herds of southeast of Iran. A total of 93 sera samples were collected between 2011 and 2012. Antibodies to BTV in sera were detected by using a commercial competitive ELISA 3 according to manufacturer's instructions.

RESULTS

The seroprevalence rates were 67.7% for goats. Within a herd, prevalence of BTV seropositive animals ranged from 33.3% to 100.0%. All goat flocks were positive to BTV antibodies.

CONCLUSIONS

This study describes a high seroprevalence rate of BTV in goat flocks in southeast of Iran for the first time.

Emergence of Bluetongue Virus Serotype 1 in French Corsica Island in September 2013

Since 2000, French Corsica Island has been exposed to the emergence of three different BT virus (BTV) serotypes: serotype 2 in 2000 and 2001, serotype 4 in 2003 and serotype 16 in 2004. Between 2005 and August 2013, no outbreaks have been reported in the French Island. At the beginning of September 2013, sheep located in the south of the island showed clinical signs suggestive of BTV infection. Laboratory analyses identified the virus as BTV serotype 1. Phylogenetic studies showed that the sequences of this strain are closely related to the BTV-1 strain that was circulating in the Mediterranean basin and in Sardinia in 2012.

Control of bluetongue in Europe

Since 1998, bluetongue virus (BTV) serotypes 1, 2, 4, 6, 8, 9, 11 and 16 have spread throughout Europe. In 2006, BTV serotype 8 (BTV-8) emerged unexpectedly in northern Europe throughout a region including Belgium, France, Germany, Luxembourg and the Netherlands. In the following year, it spread rapidly throughout the rest of Europe. In 2008, two more BTV serotypes were detected in northern Europe: BTV-6 in the Netherlands and Germany and BTV-11 in Belgium. The European incursion of BTV has caused considerable economic losses, comprising not only direct losses from mortality and reduced production but also indirect losses because of ensuing bans on trade of ruminants between BTV-infected and non-infected areas. Given the significance of the disease, all affected countries have established control and eradication measures, which have evolved with the availability of detection and prevention tools such as vaccines. Before 2005, BTV vaccination campaigns in affected countries used only modified live virus vaccines and only sheep were vaccinated, except in Italy, where all susceptible domestic ruminant species were included. After 2005, inactivated vaccines became available and cattle and goats were included in the vaccination campaigns. This review looks at how bluetongue disease has evolved in Europe and how effective vaccination strategies have been.

Screening of oomycete fungi for their potential role in reducing the biting midge (Diptera: Ceratopogonidae) larval populations in Hervey Bay, Queensland, Australia

Biting midges are globally distributed pests causing significant economic losses and transmitting arbovirus diseases to both animals and humans. Current biological and chemical control strategies for biting midge target destruction of adult forms, but strategies directed at immature stages of the insect have yet to be explored in Australia. In the present study, coastal waters of Hervey Bay region in Queensland, Australia were screened to detect the habitats of biting midge at immature stages. These results were then correlated to local environmental conditions and naturally occurring entomopathogenic fungal flora, in particular the Oomycete fungi, to determine their reducing effect on insect immature stages in the search for biological control agents in the region. The dominant species of biting midge found within this study was Culicoides subimmaculatus occuring between mean high water neaps and mean high water spring tide levels. Within this intertidal zone, the presence of C. subimmaculatus larvae was found to be influenced by both sediment size and distance from shore. Halophytophthora isolates colonized both dead and alive pupae. However, the association was found to be surface colonization rather than invasion causing the death of the host. Lack of aggressive oomycete fungal antagonists towards midge larvae might correlate with increased incidences of biting midge infestations in the region.

Molecular epidemiology of bluetongue virus serotype 1 isolated in 2006 from Algeria

This study reports on an outbreak of disease that occurred in central Algeria during July 2006. Sheep in the affected area presented clinical signs typical of bluetongue (BT) disease. A total of 5245 sheep in the affected region were considered to be susceptible, with 263 cases and thirty-six deaths. Bluetongue virus (BTV) serotype 1 was isolated and identified as the causative agent. Segments 2, 7 and 10 of this virus were sequenced and compared with other isolates from Morocco, Italy, Portugal and France showing that they all belong to a 'western' BTV group/topotype and collectively represent a western Mediterranean lineage of BTV-1.

Intragenic recombination as a mechanism of genetic diversity in bluetongue virus

Bluetongue (BT), caused by Bluetongue virus (BTV), is an economically important disease affecting sheep, deer, cattle, and goats. Since 1998, a series of BT outbreaks have spread across much of southern and central Europe. To study why the epidemiology of the virus happens to change, it is important to fully know the mechanisms resulting in its genetic diversity. Gene mutation and segment reassortment have been considered as the key forces driving the evolution of BTV. However, it is still unknown whether intragenic recombination can occur and contribute to the process in the virus. We present here several BTV groups containing mosaic genes to reveal that intragenic recombination can take place between the virus strains and play a potential role in bringing novel BTV lineages.

Bluetongue in Belgium: episode II

Bluetongue (BT) is an arthropod-borne viral disease of ruminants. In August 2006, domestic ruminant populations in Northern Europe became infected with BT virus serotype 8 (BTV-8). The first BTV-8-case of the year 2007 in Belgium was notified in July. This case was the starting point of a second wave of BT outbreaks. The main objective of this study was to describe the evolution and the clinical impact of the second episode of BT in Belgium. In addition, the main differences with the previous episode (August-December 2006) are reported. Both outbreak and rendering plant data were analysed. Overall cumulative incidence at herd level was estimated at 11.5 (11.2-11.8) and 7.5 (7.3-7.8) per cent in cattle and sheep populations respectively. The findings went in favour of a negative association between within-herd prevalence in 2006 and the risk of showing clinical signs of BT in 2007 (via protective immunity). A high level of correlation was demonstrated between BT incidence and small ruminant mortality data when shifting the latter of 1-week backwards. This result supports the hypothesis that the high increase in small ruminant mortality observed in 2007 was the consequence of the presence of BT. For cattle, the correlation was not as high. An increase in cattle foetal mortality was also observed during the year 2007 and a fair correlation was found between BT incidence and foetal mortality.

Incursion and range expansion in the bluetongue vector Culicoides imicola in the Mediterranean basin: a phylogeographic analysis

The bluetongue (BT) vector Culicoides imicola Kieffer (Diptera: Ceratopogonidae) has undergone widespread range expansion across most of the Mediterranean basin, concomitant with the largest BT epizootic outbreaks on record. Knowledge of the substructure of this vector expansion would be useful for identifying specific source-expansion systems. To this end we analysed the haplotype diversity of the mitochondrial cytochrome oxidase I gene in 273 C. imicola from 88 Mediterranean sites and outgroups. All the C. imicola haplotypes (n = 26) formed a single, distinct clade in comparison with haplotypes of four other species of the Imicola group from southern Africa, confirming C. imicola as a single phylospecies. Haplotype distribution showed extreme differentiation across the Mediterranean basin, with four common haplotypes each predominating in different areas. Eastern and western areas characterized by distinct BT incursions accounted for most of the molecular variance in haplotype composition. Shared common haplotypes identified one area of incursion and expansion encompassing the western half of the Mediterranean basin, with evidence of population growth, and another system encompassing Anatolian Turkey, the Aegean Islands and mainland Greece. A third area of range expansion was identified in the central Mediterranean, with a possible source in Algeria and unsampled parts of central North Africa. We conclude that the expansion of C. imicola in the Mediterranean basin consists of at least three incursions followed by expansions and that the western system experiences conditions promoting high population growth.

Estimating the temporal and spatial risk of bluetongue related to the incursion of infected vectors into Switzerland

Background

The design of veterinary and public health surveillance systems has been improved by the ability to combine Geographical Information Systems (GIS), mathematical models and up to date epidemiological knowledge. In Switzerland, an early warning system was developed for detecting the incursion of the bluetongue disease virus (BT) and to monitor the frequency of its vectors. Based on data generated by this surveillance system, GIS and transmission models were used in order to determine suitable seasonal vector habitat locations and risk periods for a larger and more targeted surveillance program.

Results

Combined thematic maps of temperature, humidity and altitude were created to visualize the association with Culicoides vector habitat locations. Additional monthly maps of estimated basic reproduction number transmission rates (R₀) were created in order to highlight areas of Switzerland prone to higher BT outbreaks in relation to both vector activity and transmission levels. The maps revealed several foci of higher risk areas, especially in northern parts of Switzerland, suitable for both vector presence and vector activity for 2006.

Results showed a variation of R₀ values comparing 2005 and 2006 yet suggested that Switzerland was at risk of an outbreak of BT, especially if the incursion arrived in a suitable vector activity period. Since the time of conducting these analyses, this suitability has proved to be the case with the recent outbreaks of BT in northern Switzerland.

Conclusion

Our results stress the importance of environmental factors and their effect on the dynamics of a vector-borne disease. In this case, results of this model were used as input parameters for creating a national targeted surveillance program tailored to both the spatial and the temporal aspect of the disease and its vectors. In this manner, financial and logistic resources can be used in an optimal way through seasonally and geographically adjusted surveillance efforts. This model can serve as a tool for other vector-borne diseases including human zoonotic vectors which are likely to spread into Europe.

Bluetongue in Europe and the Mediterranean Basin: history of occurrence prior to 2006

Bluetongue virus (BTV) exists around the world in a broad band covering much of the Americas, Africa, southern Asia and northern Australia. Historically, it also occasionally occurred in the southern fringes of Europe. It is considered to be one of the most important diseases of domestic livestock. Recently BTV has extended its range northwards into areas of Europe never before affected and has persisted in many of these locations causing the greatest epizootic of bluetongue (BT), the disease caused by BTV, on record. Indeed, the most recent outbreaks of BT in Europe are further north than this virus has ever previously occurred anywhere in the world. The reasons for this dramatic change in BT epidemiology are complex but are linked to recent extensions in the distribution of its major vector, Culicoides imicola, to the involvement of novel Culicoides vector(s) and to on-going climate-change. This paper investigates these recent outbreaks in the European theatre, up to the beginning of 2006, highlights prospects for the future and sets the scene for the following papers in this special issue.

Vaccines against bluetongue in Europe

After the incursion of bluetongue virus (BTV) into European Mediterranean countries in 1998, vaccination was used in an effort to minimize direct economic losses to animal production, reduce virus circulation and allow safe movements of animals from endemic areas. Vaccination strategies in different countries were developed according to their individual policies, the geographic distribution of the incurring serotypes of BTV and the availability of appropriate vaccines. Four monovalent modified live virus (MLV) vaccines were imported from South Africa and subsequently used extensively in both cattle and sheep. MLVs were found to be immunogenic and capable of generating strong protective immunity in vaccinated ruminants. Adverse side effects were principally evident in sheep. Specifically, some vaccinated sheep developed signs of clinical bluetongue with fever, facial oedema and lameness. Lactating sheep that developed fever also had reduced milk production. More severe clinical signs occurred in large numbers of sheep that were vaccinated with vaccine combinations containing the BTV-16 MLV, and the use of the monovalent BTV-16 MLV was discontinued as a consequence. Abortion occurred in <0.5% of vaccinated animals. The length of viraemia in sheep and cattle that received MLVs did not exceed 35 days, with the single notable exception of a cow vaccinated with a multivalent BTV-2, -4, -9 and -16 vaccine in which viraemia persisted at least 78 days. Viraemia of sufficient titre to infect Culicoides insects was observed transiently in MLV-vaccinated ruminants, and natural transmission of MLV strains has been confirmed. An inactivated vaccine was first developed against BTV-2 and used in the field. An inactivated vaccine against BTV-4 as well as a bivalent vaccine against serotypes 2 and 4 were subsequently developed and used in Corsica, Spain, Portugal and Italy. These inactivated vaccines were generally safe although on few occasions reactions occurred at the site of inoculation. Two doses of these BTV inactivated vaccines provided complete, long-lasting immunity against both clinical signs and viraemia, whereas a single immunization with the BTV-4 inactivated vaccine gave only partial reduction of viraemia in vaccinated cattle when challenged with the homologous BTV serotype. Additional BTV inactivated vaccines are currently under development, as well as new generation vaccines including recombinant vaccines.

Development and initial evaluation of a real-time RT-PCR assay to detect bluetongue virus genome segment 1

Since 1998, multiple strains of bluetongue virus (BTV), belonging to six different serotypes (types 1, 2, 4, 8, 9 and 16) have caused outbreaks of disease in Europe, causing one of the largest epizootics of bluetongue ever recorded, with the deaths of >1.8 million animals (mainly sheep). The persistence and continuing spread of BTV in Europe and elsewhere highlights the importance of sensitive and reliable diagnostic assay systems that can be used to rapidly identify infected animals, helping to combat spread of the virus and disease. BTV has a genome composed of 10 linear segments of dsRNA. We describe a real-time RT-PCR assay that targets the highly conserved genome segment 1 (encoding the viral polymerase--VP1) that can be used to detect all of the 24 serotypes, as well as geographic variants (different topotypes) within individual serotypes of BTV. After an initial evaluation using 132 BTV samples including representatives of all 24 BTV serotypes, this assay was used by the European Community Reference Laboratory (CRL) at IAH Pirbright to confirm the negative status of 2,255 animals imported to the UK from regions that were considered to be at risk during the 2006 outbreak of BTV-8 in Northern Europe. All of these animals were also negative by competition ELISA to detect BTV specific antibodies and none of them developed clinical signs of infection. These studies have demonstrated the value of the assay for the rapid screening of field samples.

Molecular epidemiology of bluetongue virus in Portugal during 2004-2006 outbreak

After 44 years of epidemiological silence, bluetongue virus (BTV) was reintroduced in Portugal in the autumn of 2004. The first clinical cases of bluetongue disease (BT) were notified in sheep farms located in the South of Portugal, close to the Spanish border. A total of six BTV, five of serotype 4 and one of serotype 2 were isolated from sheep and cattle during the 2004-2006 epizootics. The nucleotide sequence of gene segments L2, S7 and S10 of BTV-4 prototype strain (BTV4/22045/PT04) obtained from the initial outbreak and of BTV-2 (BTV2/26629/PT05) was fully determined and compared with those from other parts of the world. The phylogenetic analysis revealed that BTV4/22045/PT04 is related to other BTV-4 strains that circulate in the Mediterranean basin since 1998, showing the highest identity (99%) with BTV-4 isolates of 2003 from Sardinia and Corsica, whereas BTV2/26629/PT05 is almost indistinguishable from the Onderstepoort BTV-2 live-attenuated vaccine strain and its related field strain isolated in Italy. Since live-attenuated BTV-2 vaccine was never used in Portugal, the isolation of this strain may represent a natural circulation of the vaccine virus used in other countries in Mediterranean Europe.

Molecular epidemiology of bluetongue virus serotype 4 isolated in the Mediterranean Basin between 1979 and 2004

The nucleotide sequences of genome segments 2, 7, 8, 9 and 10, coding for viral proteins (VP) and non-structural proteins (NS)--VP2, VP7, NS2, VP6 and NS3/NS3A, respectively, were determined and compared for 10 strains of bluetongue virus (BTV) serotype 4 isolated in the Mediterranean Basin between 1979 and 2004, and the South African attenuated BTV 4 vaccine strain. The sequence data generated for the BTV 4 strains isolated in Greece in 1979, 1999 and 2000 showed that they had a common origin but were distinct from the lineage of the BTV 4 strains isolated from 2003 onward in the western Mediterranean Basin (Italy, Morocco, Spain and Corsica). The nucleotide and deduced amino acid (aa) sequences of the BTV 4 strains within each lineage were identical to each other, irrespective of the year of isolation or the geographical location. Although the sequence of VP2 from the Turkish and Greek strains were highly similar, there were sufficient differences in the VP6, VP7 and NS2 proteins to suggest that the Turkish BTV 4 belongs to a third lineage. Alignment of the NS3 sequences from the attenuated BTV 4 vaccine strain and the field strains showed 13 aa substitutions, which may, either singularly or together, be responsible for attenuation and hence determining the virulence of the virus.

Performance evaluation of a competitive ELISA test used for Bluetongue antibody detection in France, a recently infected area

In 1998, bluetongue (BT) was introduced in northern Africa and then extended to northern latitudes including the French island of Corsica. Following the outbreaks in Corsica in 2000 and 2001, cross-sectional studies and surveillances have been set up in Corsica and also in the southern part of mainland France, a disease-free area but considered at high risk because of its proximity. The surveillance was based on regular blood sampling of susceptible species and antibody detection by a commercial competitive ELISA kit (cELISA). The performance of this cELISA was evaluated on both field results obtained during the 2001 surveillance campaigns and experimental results. ROC analyses were carried out using RT-PCR results as gold standard for determining the infection status of animals. From all these sets of data, cut-off values optimising the diagnostic accuracy of the test were computed. Their values ranged around the manufacturer's 50% threshold from 41% to 63%. The area under the ROC curve obtained from field data was 0.843 (95% CI: 0.762-0.923). In all our results, it appeared also that the specificity of the cELISA test was always perfect if the cut-off was at least at 80%. This cELISA test does not seem sufficient to diagnose BT disease in animals with BT-like symptoms. However, complementary data are needed to better estimate sensitivity and specificity values of this BT test for its use either as a diagnostic tool in infected areas or as a screening test in BT-free areas. The use and validity of RT-PCR results as gold standard are discussed. As the lack of suitable data strongly limited the applicable analyses, a discussion based on the OIE recommendations about test evaluation is initiated.

Molecular Diagnosis of Granulocytic Anaplasmosis and Infectious Cyclic Thrombocytopenia by PCR-RFLP

Anaplasma phagocytophilum (A. phagocytophilum, formerly Ehrlichia phagocytophila) is a tick-borne pathogen responsible for tick-borne fever in ruminants, equine granulocytic ehrlichiosis (EGE) in horses, canine granulocytic ehrlichiosis (CGE) in dogs, and for human granulocytic ehrlichiosis (HGE). Human cases have been registered in many countries with a broad range of symptoms and pathogenicity. This article focused on Sardinia as the prevalence in humans was almost seven times higher than in the rest of Italy. To evaluate the risk, blood samples were collected from dogs and horses on the island. Genomic DNA was extracted from the buffy coat and amplified by heminested polymerase chain reaction (PCR) using the groEL gene primers. The first PCR reaction amplified a 624-bp fragment for both A. phagocytophilum and A. platys while the second PCR reaction amplified 573-bp and 515-bp fragments for the above two pathogens, respectively. Six A. phagocytophilum samples were PCR positive (3 dogs and 3 horses) while another dog was A. platys PCR positive. A phylogenetic analysis was conducted with A. phagocytophilum sequences in GenBank from the United States, Slovenia, Switzerland, Germany, UK, Austria, and Czech Republic. Surprisingly, the related phylogenetic tree showed that the Sardinian isolates were closer to the American isolates, which were showing highest mortality rates than from the other two European lineages.

No evidence of bluetongue virus in Switzerland

We report the results of the first survey for antibody against bluetongue virus (BTV) that was conducted in Switzerland in the year 2003. In a nationwide cross-sectional study with partial verification, 2437 cattle sera collected from 507 herds were analysed using competitive enzyme-linked immunosorbent assays (c-ELISA). To adjust for misclassification, 158 sera, including 86 that were recorded equivocal in Switzerland, were sent to the Office Internationale des Epizooties designated regional reference laboratory in the UK for confirmation. No BTV antibody was detected in any of these samples, confirming the absence of BTV from Switzerland in 2003. The specificity of the c-ELISA used in Switzerland for individual Swiss cattle was calculated to be 96.5%. The mean herd sensitivity achieved in our survey ranged from 78.9% to 98.8% depending on the with-in herd prevalence and test sensitivity used for the calculations. The cumulated confidence level achieved with the survey based on a minimal expected prevalence of 2%, was 99.99% and therefore it was concluded that there was no evidence of BTV circulation in Switzerland in 2003.

Bluetongue vector species of Culicoides in Switzerland

Switzerland is historically recognized by the Office Internationale des Epizooties as free from bluetongue disease (BT) because of its latitude and climate. With bluetongue virus (BTV) moving north from the Mediterranean, an entomological survey was conducted in Switzerland in 2003 to assess the potential of the BTV vectors present. A total of 39 cattle farms located in three geographical regions, the Ticino region, the Western region and the region of the Grisons, were monitored during the vector season. Farms were located in areas at high risk of vector introduction and establishment based on the following characteristics: annual average temperature > 12.5 degrees C, average annual humidity >or= 60%, cattle farm. Onderstepoort black light traps were operated at the cattle farms generally for one night in July and one night in September. A total of 56 collections of Culicoides (Diptera: Ceratopogonidae) were identified morphologically. Only one single individual of Culicoides (Avaritia) imicola, the major Old World vector of BTV, was found in July 2003 in the Ticino region, one of the southernmost regions of Switzerland. In the absence of further specimens of C. imicola from Switzerland it is suggested that this individual may be a vagrant transported by wind from regions to the south of the country where populations of this species are known to occur. Alternative potential BTV vectors of the Culicoides (Culicoides) pulicaris and Culicoides (Avaritia) obsoletus complexes were abundant in all sampled regions with individual catches exceeding 70 000 midges per trap night.

Bluetongue virus in the French Island of Reunion

This paper records the results of a bluetongue virus (BTV) serological survey and reports the first isolation of BTV on the French Island of Reunion. In January 2003, the French Island of Reunion, located off the coast of Madagascar, reported an outbreak of disease in cattle that resembled clinical bluetongue (BT) in sheep. The suspected causal agent was isolated and identified as epizootic haemorrhagic disease of deer virus (EHDV). However, because of the similarity in the clinical signs to those of BT, a retrospective survey against BTV was carried out using sera collected in 2002. Results revealed the presence of antibody in all sera tested indicating that BTV has been resident on the Island since 2002, and probably earlier. Although up to July 2003 no clinical BT had ever been reported in sheep, BTV viral RNA was amplified by RT-PCR from a single sheep blood collected in February that year, which strongly suggested that BTV was currently circulating on the Island. Following a second outbreak of disease in August 2003, this time involving a flock of Merino sheep, infectious BTV was finally isolated, and identified by both traditional and molecular techniques as serotype 3. The nucleotide and amino-acid sequences of the RT-PCR products amplified for BTV segments 7 and 10 from the sheep blood collected in February and August from different areas of the Island, were sufficiently diverse as to suggest that they were of different origins and/or different BTV serotypes.