Table 10.
Assessment of the conclusions from the EFSA opinion on bluetongue vectors and insecticides (EFSA, 2008), (left column), and their endorsement or the new modified version (right column)
| Conclusions from EFSA opinion (2008) | Endorsement or new version of the conclusions |
|---|---|
| The distribution of the main vector species is well known in each of the BTV affected countries | No precise distribution maps are yet available, but maps will be available in the framework of Vectornet projecta. However, there is still a need to know detailed distribution of the species included in the Obsoletus assemblage (C. obsoletus, C. scoticus, C. chiopterus and C. dewulfi) |
| The distribution of C. imicola is well documented in the southern European countries. | According to phylogeographical studies, this species has been present in the Mediterranean basin for 10,000 years and in southern Europe for at least 100 years. Therefore, the concept of recent invasion seems to be not valid for the European Mediterranean countries. The northward expansion of this species seems to be very limited in France, and inexistent in Italy |
| The distribution of C. obsoletus/C. scoticus includes all the countries in Europe, although it is relatively more abundant in the northern regions. In the southern regions of Europe, the distributions of C. imicola and C. obsoletus/C. scoticus overlap | This conclusion is still valid |
| C. dewulfi, C. chiopterus and C. pulicaris (sometimes not differentiated from C. lupicaris) are also widespread in Europe, especially in the northern countries. Nevertheless, their abundance as estimated on the basis of light traps has been always reported as being lower than C. obsoletus/C. scoticus, except in Mediterranean areas where C. imicola and/or C. newsteadi is usually dominant | This conclusion is still valid |
| Present data indicate that the biting activity of the majority of the vector species in Europe primarily occurs during the crepuscular and nocturnal hours | This conclusion is still valid |
| There are indications, however, that under suitable meteorological conditions and particularly during the latter part of the season, diurnal feeding activity of potential vector species of Culicoides may occur | This conclusion is still valid |
| The implications for BTV transmission of vector daylight activity are at present unclear as trapping programmes based only on light traps are not adequate to provide information regarding the daylight biting activity | Recent studies suggest that daylight biting activity is limited and not relevant compared to the crepuscular activity. However, in some scenarios day activity may underestimate BTV‐infected females which will be not captured by UV traps |
| Dispersion of vector species of Culicoides at the farm level is still very poorly understood, but assumed to be short distances from the breeding sites | The dispersion of Culicoides may be higher than originally thought |
| Long distance dispersion of vector Culicoides on winds over scores or even hundreds of km has been reported by several workers but the proportion of a population that are involved is thought to be very small. | This conclusion is still valid |
| Distribution and abundance data almost solely obtained by only using UV light traps may underestimate some species important for the transmission of BTV | This conclusion is still valid |
| Northern Palaearctic species of Culicoides are able to transmit BTV | This conclusion is still valid |
| To date, the specific vector(s) of BTV in these areas have not been identified, although strong circumstantial evidence implicates C. obsoletus, C. scoticus, C. dewulfi, C. chiopterus and species of the Pulicaris assemblage as the likeliest candidates. This list is probably not exhaustive and the identification of additional vector species is likely | Further studies (PCR detection) have given more evidence of the role as vectors of the Obsoletus and Pulicaris assemblages |
| To date, standardised and appropriate testing protocols to determine the vector competence levels of Culicoides species for BTV in Europe have not been applied. In northern Europe this has led to the use of pool‐based real‐time RT‐PCR investigations on field‐caught parous female midges to imply vector competence levels | This conclusion is still valid for all EU (north and south) |
| These methods have several technical drawbacks and do not provide a measure of vector transmission in the field. Similarly, studies from southern Europe, based around cell‐based isolation of virus, while superior to those using real‐time RT‐PCR, are still difficult to interpret due to the use of pool‐based isolation methods and an inability to accurately assess viral dissemination levels | This conclusion is still valid |
| Recent publications that allow high‐throughput processing of Culicoides for virus isolation may allow some of these issues to be addressed and also enable standardisation between laboratories | This conclusion is still valid |
| Laboratory‐based studies on vector competence remain time consuming and difficult to perform outside the areas of BTV transmission as they require specialist laboratory accommodation | This conclusion is still valid |
| Vector competence is just one element of the vector capacity of a species for BTV transmission. Other elements some of which have been assessed in southern Europe include host preferences, biting rates, vector survival, location of breeding sites, temporal and spatial distribution, and abundance | Host preferences, biting rates, location of breeding sites, temporal distribution and abundance are currently known for the major vector species in whole Europe. More updated spatial distribution of vectors will be available from the work done by the Vectornet project |
| An integrated assessment of all of these elements is required to gain a realistic idea of the importance of each potential vector species | This conclusion is still valid |