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1.
Following the spread of Bluetongue virus (BTV) in many Mediterranean countries during the last 5 years, presence of the main BTV vector, Culicoides imicola Kieffer (Diptera: Ceratopogonidae), was recorded in the region, including the island of Sardinia where the first BT epidemic originally started in the year 2000. Several models were also designed based on climate variables and satellite imaging in order to predict the presence and abundance of BTV vectors across Europe. A 3 years entomological survey (2001-2003) was conducted in the southern part of Sardinia confirming the widespread presence of C. imicola. However, substantial differences in terms of relative abundance were observed between field data and prediction maps based on satellite-derived climate variables. Distribution of other potential BT vectors, belonging to Culicoides obsoletus Meigen and Culicoides pulicaris Linnaeus groups was also not congruent with model-based predictions. These results stress the need of taking into account additional environmental factors (such as soil type, land usage, etc.) and local microclimatic conditions, especially related to breeding site requirements of Culicoides species, in order to predict the presence and abundance of BT vectors and to design reliable prediction maps on a local scale.  相似文献   

2.
Bluetongue (BT) and African Horse Sickness (AHS) are infectious arthropod-borne viral diseases affecting ruminants and horses, respectively. Culicoides imicola Kieffer, 1913, a biting midge, is the principal vector of these livestock diseases in Africa and Europe. Recently bluetongue disease has re-emerged in the Mediterranean Basin and has had a devastating effect on the sheep industry in Italy and on the islands of Sicily, Sardinia, Corsica and the Balearics, but fortunately, has not penetrated onto mainland France and Spain. To survey for the presence of C. imicola, an extensive light-trap network for the collection of Culicoides, was implemented in 2002 in southern mainland France. The morphological identification of Culicoides can be both tedious and time-consuming because its size ranges from 1.5 to 3 mm. Therefore, an ITS1 rDNA polymerase chain reaction (PCR)-based diagnostic assay was developed to rapidly and reliably identify Culicoides spp. and C. imicola. The aim of this work was to set up a rapid test for the detection of C. imicola amongst a pool of insects collected in areas at risk for BT. The sequence similarity of the rDNA (nuclear ribosomal DNA), which is greater within species than between species, is the foundation of its utilisation in species-diagnostic assays. The alignment of the 11 ITS1 sequences of Culicoides obtained from Genbank and EMBL databases helped us to identify one region in the 5' end and one in the 3' end that appear highly conserved. PCR primers were designed within these regions to amplify genus-specific fragments. In order to set up a C. imicola-specific PCR, another forward primer was designed and used in combination with the previously designed reverse primer. These primers proved to be highly specific and sensitive and permitted a rapid diagnostic separation of C. imicola from Culicoides spp.  相似文献   

3.
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.  相似文献   

4.
Bluetongue virus in the Mediterranean Basin 1998-2001   总被引：4，自引：0，他引：4  
Bluetongue (BT) exists around the world in a broad band covering much of the Americas, Africa, southern Asia, northern Australia and, occasionally, the southern fringe of Europe. It is considered to be one of the most important diseases of domestic livestock. Recently the virus causing this disease 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 the disease on record. The reasons for this dramatic change in BT epidemiology are complex but are linked to recent extensions in the distribution of its major vector, Culicoidesimicola, to the involvement of novel Culicoides vector(s) and to an apparent ability of the virus to overwinter in the absence of adult vectors. In addition, the effects of these changes have been exacerbated by problems in control, particularly in relation to vaccination. This paper explores these areas and highlights prospects for the future.  相似文献   

5.
Bluetongue (BT) is a vector-borne animal disease of economical importance due to the international trade restrictions likely to be put into place in a country once the infection is discovered. The presence of BT and its vectors in countries adjacent to Switzerland stresses the need of implementing a surveillance system and to raise disease awareness among potential stakeholders. A national survey in Switzerland 2003 indicated freedom of Bluetongue virus (BTV), although a single individual of the main BT vector Culicoides imicola was caught in the canton of Ticino. The survey also demonstrated that potential BT vectors, C. obsoletus and C. pulicaris are locally abundant in Switzerland. Therefore, a new surveillance method based on sentinel herds in high risk areas was implemented in 2004 for the early detection of both an incursion of BT vectors into Switzerland, and potential virus circulation among cattle.  相似文献   

6.
Using a geographic information system (GIS), by analysis of the relationship between the spatial distribution of cattle density and the risk factors temperature, altitude and rainfall, we defined geographical habitats enabling optimal development and competence of Culicoides spp. to transmit Bluetongue-Virus (BTV): Risk zones (low, high, highest risk) were identified mainly in Baden-Württemberg, Hessen and Rheinland-Pfalz if persistently infected ruminants are imported into these zones in summer (June to August mainly), based on the current climatic conditions, BTD outbreaks are considered a real possibility. Overwintering of the virus seems unlikely. However, global warming will lead to a steady increase of the size of the risk zones. In addition, the possibility of primary outbreaks increases. The reason for this is not only the expected northern shift of Culicoides imicola, but in addition an increasing vector competence of domestic Culicoides species. We therefore recommend the storage of vaccines as well as conducting ecological studies analysing the presence of Culicoides vectors. Using the data from these studies, it will be possible to produce updated quantitative risk assessment via GIS.  相似文献   

7.
In August 2000 bluetongue (BT) disease appeared amongst sheep on the island of Sardinia spreading later to Sicily and to mainland Italy. The majority of areas affected by BT were surveyed for Culicoides imicola, the only proven vector of the disease known to occur in the Mediterranean region. The data from 1456 light-trap collections, made in months with a mean temperature of 12.5 degrees C, were used to test the accuracy of current models predicting the prevalence and abundance of C. imicola across the region. For Italy, the distribution of C. imicola was found to be very irregular and did not fit the modelled predictions. The possible reasons for this are discussed, and suggestions made as to which variables may improve this fit in the development of future risk models. In Italy, past surveys failed to reveal the presence of C. imicola, and so could be construed as evidence of its recent invasion, and thus rampant spread northwards. Although equivocal, historical records indicate that C. imicola was overlooked in the past. Six recommendations are made as to the possible future course of Culicoides research in southern Europe.  相似文献   

8.
蓝舌病是由蓝舌病毒(BTV)引起的一种非接触性传染病,主要侵害反刍动物,库蠓是蓝舌病毒传播最重要的媒介生物。本研究基于尖喙库蠓地理分布数据及环境数据,利用最大熵生态位模型(MaxEnt)对尖喙库蠓在中国大陆的分布情况进行了预测,并评估了环境变量对尖喙库蠓分布的影响。结果显示,最适合尖喙库蠓生存的地区主要分布在中国的西北和东北部分地区,以及南方的大部分地区;Jackknife分析结果显示,土壤有效水含量(25%)、最冷月最低温(18.1%)、最干月降雨量(18%)、平均最大风速(13.2%)是影响尖喙库蠓分布最主要的4个环境因子,其中最干月降雨量是模型中影响尖喙库蠓分布的最重要环境变量。本研究首次将这种生态位模型用于预测中国库蠓的分布,为蓝舌病的预防控制工作提供参考依据,同时也为库蠓监测管理提供信息。  相似文献   

9.
Changes in the distribution and abundance of insects are likely to be amongst the most important and immediate effects of climate change. We review here the risk that climate change poses to the UK's livestock industry via effects on Culicoides biting midges, the vectors of several arboviruses, including those that cause bluetongue (BT) and African horse sickness (AHS). The major old-world vector of BT and AHS viruses, C. imicola, occurs in southern Europe and will spread further north as global temperatures increase. It is unlikely, however, that in the foreseeable future it will reach and become established in the UK. As the distribution of C. imicola moves north, however, it may bring BT and AHS viruses into the range of other Culicoides species that are known to be competent vectors and which occur much further north. Once infected via this 'baton effect', these species may be able to spread the viruses over much of Europe, including the UK. Climate change may increase their vector competence further and will also increase the likelihood of viruses surviving from one year to the next. An additional risk is that the predicted increase in the frequency of short periods of hot temperatures may lead to the creation of novel vector species, by removing the barriers that in colder conditions make them refractory to viral infection.  相似文献   

10.
The identification of premises that may play an important role in the introduction or spread of animal diseases is fundamental to the development of risk-based surveillance and control programs. A combination of geo-statistical and cluster analysis methods was used to identify geographical areas and periods of time at highest risk for introduction of the African horse sickness virus (AHSV) into the Castile and Leon (CyL) region of Spain. Risk was estimated based on the predicted premises-specific abundance of Culicoides spp., a vector for AHSV, and on the frequency of equine introductions from outside regions. The largest abundance of Culicoides spp. was observed between May and September in the northern region of CyL. Six significant (P-value <0.01) space-time clusters of equine premises were found, at which presence of Culicoides spp. was predicted and live equidae were introduced from outside CyL. The clusters included 37 equine premises and took place between April and December. These results will contribute to updating plans for prevention of AHSV introduction and spread in Spain. The methodological approach developed here may be adapted and applied to design and establish risk-based surveillance and control programs for Spain and other European countries.  相似文献   

11.
Swiss Bluetongue surveillance from mid 2007 to mid 2008 was a combination of monthly bulk milk testing of 200 cattle herds in zones of higher risk for vector presence and intensification of passive clinical surveillance. The spatial scan statistic and Moran's I statistic were used to determine clustering of surveillance data. The results show a high level of surveillance intensity for BT in Switzerland in 2007. In the region encompassing the Cantons of Aargau, Basel-Landschaft, Basel-Stadt and Solothurn, where cases were detected in 2007, the surveillance was significantly higher than in the rest of Switzerland. Six cases of Bluetongue were detected within the surveillance system. The prevalence estimates 9.62% (95% CI = 3.25%-18.85% versus 0.98% (95% CI = 0.2%-2.22%) were also significantly higher in the area with higher surveillance intensity. Spatial variation in surveillance data should to be considered if a disease event is analysed on a national scale. The spatial variation of prevalence estimates should be considered in future Bluetongue surveillance in Switzerland.  相似文献   

12.
Bluetongue is an infectious, non-contagious arboviral disease thought to infect all known ruminant species. Since 1998, an unprecedented epizootic of the disease has occurred in the Mediterranean region, resulting in the deaths of over 800,000 sheep to date. Bluetongue virus (BTV) is transmitted by biting midges of which one species, Culicoides imicola, is the major vector in the old world. C. imicola was trapped for 2 years at 87 sites across Portugal and models were developed for predicting the presence and abundance of the midge at these sites. Discriminant analysis was used to identify the best models from 40 temporally Fourier-processed 1 km spatial resolution remotely-sensed variables. The best models correctly predicted presence and absence at 83 of the 87 sites, and abundance at 76 sites. The models were then used to predict C. imicola presence and abundance elsewhere across Europe and north Africa. C. imicola was predicted to be present and in high abundance at the majority of areas affected in the recent bluetongue epizootic, including the Balearics, Sardinia, Corsica, Sicily, areas of mainland Italy, large areas of Greece, western Turkey and northern Algeria and Tunisia.  相似文献   

13.
ABSTRACT: African horse sickness is an economically highly important non-contagious but infectious Orbivirus disease that is transmitted by various species of Culicoides midges. The equids most severely affected by the virus are horses, ponies, and European donkeys; mules are somewhat less susceptible, and African donkeys and zebra are refractory to the devastating consequences of infection. In recent years, Bluetongue virus, an Orbivirus similar to African horse sickness, which also utilises Culicoides spp. as its vector, has drastically increased its range into previously unaffected regions in northern Europe, utilising indigenous vector species, and causing widespread economic damage to the agricultural sector. Considering these events, the current review outlines the history of African horse sickness, including information concerning virus structure, transmission, viraemia, overwintering ability, and the potential implications that an outbreak would have for Ireland. While the current risk for the introduction of African horse sickness to Ireland is considered at worst 'very low', it is important to note that prior to the 2006 outbreak of Bluetongue in northern Europe, both diseases were considered to be of equal risk to the United Kingdom ('medium-risk'). It is therefore likely that any outbreak of this disease would have serious socio-economic consequences for Ireland due to the high density of vulnerable equids and the prevalence of Culicoides species, potentially capable of vectoring the virus.  相似文献   

14.
A light-trap survey was undertaken of the species composition, seasonal abundance and parity of Culicoides at Roma, Lesotho, to establish whether the likely vectors for bluetongue and African horse sickness occur in this area as well as the chance of transmission. A total of 34 catches was made between 21 September 1985 and 24 September 1986; 32,819 Culicoides were caught belonging to 19 species. Culicoides numbers rapidly built up from December to a peak in February which implies that this may also be the optimum time for virus transmission. The number of Culicoides dropped sharply in April with the onset of cooler conditions. C. zuluensis was the dominant species forming 69.6% of the totalled catches, followed by C. pycnostictus with 11.7%. C. imicola, the only proven vector of bluetongue, was never abundant representing only 4.4% of the midges caught. The parous rate for each of the 2 commonest species was low, implying a low vector capacity.  相似文献   

15.
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16.
Bluetongue (BT) can cause severe livestock losses and large direct and indirect costs for farmers. To propose targeted control strategies as alternative to massive vaccination, there is a need to better understand how BT virus spread in space and time according to local characteristics of host and vector populations. Our objective was to assess, using a modelling approach, how spatiotemporal heterogeneities in abundance and distribution of hosts and vectors impact the occurrence and amplitude of local and regional BT epidemics. We built a reaction–diffusion model accounting for the seasonality in vector abundance and the active dispersal of vectors. Because of the scale chosen, and movement restrictions imposed during epidemics, host movements and wind-induced passive vector movements were neglected. Four levels of complexity were addressed using a theoretical approach, from a homogeneous to a heterogeneous environment in abundance and distribution of hosts and vectors. These scenarios were illustrated using data on abundance and distribution of hosts and vectors in a real geographical area. We have shown that local epidemics can occur earlier and be larger in scale far from the primary case rather than close to it. Moreover, spatial heterogeneities in hosts and vectors delay the epidemic peak and decrease the infection prevalence. The results obtained on a real area confirmed those obtained on a theoretical domain. Although developed to represent BTV spatiotemporal spread, our model can be used to study other vector-borne diseases of animals with a local to regional spread by vector diffusion.  相似文献   

17.
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18.
Bluetongue is an economically important arboviral disease of ruminants that is transmitted by hematophagous Culicoides midges. In light of dramatic recent changes in the global distribution of bluetongue virus (BTV), the goals of this study were to re-evaluate the prevalence of BTV infection of cattle and abundance of Culicoides midges on individual dairy farms in California. A serosurvey of adult dairy cattle confirmed that BTV infection is prevalent throughout much of the state, although the coastal northwestern region remains free of infection and prevalence varies markedly among farms in the remainder of the state. Intensive sampling for one year of 4 farms in the northern Central Valley of California showed that the abundance of Culicoides midges was markedly different and coincided with the prevalence of BTV infection of sentinel cattle on each farm. Mean maximum and minimum temperatures and other meteorological parameters were similar on all 4 farms, thus we speculate that particular management practices were responsible for both the increased midge abundance and prevalence of BTV infection of cattle at individual farms. Specifically, it is concluded that variation in vector abundance at individual farms most likely is the result of waste-water lagoon and irrigation management practices, leading to higher BTV infection rates among livestock held on farms with more waste-water lagoons and greater acreage of land for waste-water irrigation.  相似文献   

19.
The outbreak of bluetongue (BT) in northern Europe 2006 initiated the monitoring of vectors, biting midges of the genus Culicoides in Sweden. In order to determine the diversity, distribution and seasonal dynamics of Culicoides, weekly collections were made during 2008 and during March-December 2009 using the Ondestepoort Veterinary Institute black light trap. Twenty sampling sites were selected in 12 provinces. In total of 30,704 Culicoides were collected in 2008 and 32,252 in 2009. The most abundant species were the potential vectors of BTV Culicoides obsoletus/C. scoticus that comprised of 77% of the total catches. Other biting midges collected were Culicoides impunctatus (9%), Culicoides grisescens (3%), Culicoides punctatus (2%), Culicoides chiopterus (2%) and Culicoides pulicaris (2%). Culicoides obsoletus/C. scoticus were most abundant during May-June and August-September. The majority of the species were active from March to November in 2008 and April to October in 2009. Species considered as potential vectors of bluetongue virus (BTV) occurred as far north as latitude 65°N (Kalix).  相似文献   

20.
Bluetongue is an infectious disease of ruminants caused by a virus transmitted by biting midges, one species of which, Culicoides imicola, is the major vector in the Old World. Following an epizootic of African horse sickness,a related disease, in Iberia and Morocco between 1987 and 1991, C imicola was trapped for two years at 44 sites in the affected region and models were developed for predicting the abundance of C imicola at these sites. Discriminant analysis was applied to identify the best model of three levels of abundance from 40 Fourier-processed remotely sensed variables and a digital elevation model. The best model correctly predicted the abundance level at 41 of the 44 sites. The single most important variable was the phase of the annual cycle of the normalised difference vegetation index. The model was used to predict the abundances of C imicola elsewhere around the Mediterranean and predicted high levels of abundance in many areas recently affected by bluetongue, including the Balearics, Sardinia, Sicily, eastern Greece, western Turkey, Tunisia and northern Algeria. The model suggests that eastern Spain, the island of Ibiza, the provinces of Lazio and Puglia in Italy, the Peloponnese and parts of northern Algeria and Libya may be at risk of bluetongue in 2001.  相似文献   

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