Vector monitoring at Belgian outbreak sites during the bluetongue epidemic of 2006

In response to the first bluetongue outbreak in Belgium a monitoring programme was started at the end of August 2006 to identify possible vectors transmitting the disease. Black light traps were deployed at 36 outbreak sites and captured 1959 Culicoides specimens belonging to 16 different species. Eighty four percent of the biting midges captured belonged to the C. obsoletus complex, among them C. obsoletus s.s., C. dewulfi and C. scoticus, three suspected bluetongue vectors. The Veterinary and Agrochemical Research Centre detected viral RNA in pools of individuals belonging to this complex. Culicoides pulicaris, a potential bluetongue vector in Italy, should yet not be excluded as a possible vector in Belgium as this species was frequently found around outbreak sites, notwithstanding this species is not easily captured with the trapping techniques used during this survey.     

Indoor activity of Culicoides associated with livestock in the bluetongue virus (BTV) affected region of northern France during autumn 2006

In August 2006, bluetongue virus (BTV) was detected in the Netherlands, Belgium, western Germany, Luxembourg and northern France for the first time. Consequently, a longitudinal entomological study was conducted in the affected region of northern France (Ardennes) throughout the autumn of 2006. Data on the spatio-temporal distribution of Culicoides (Diptera: Ceratopogonidae) associated with livestock were collected and an attempt was made to identify the vector(s) involved in BTV transmission by means of virus detection in wild-caught biting midges. Weekly sampling using standardized Onderstepoort-type blacklight traps were performed simultaneously both outdoors and indoors in one BTV-free and three BTV-affected farms between September and December 2006. Culicoides were sorted according to farm, location (outdoors vs. indoors), time point (in weeks), species and physiological stage. BTV detection was conducted by RT-PCR on monospecific pools of non-bloodfed parous female Culicoides. The principal results showed: (i) the absence of the Mediterranean vector, C. imicola, (ii) the relatively low abundance of C. dewulfi and C. pulicaris, (iii) the widespread occurrence and abundance of C. obsoletus/C. scoticus with longevity and behaviour compatible with BTV transmission, and (iv) all Culicoides pools tested for BTV were negative. In France, the very low levels of BTV-8 circulation were probably due to the limited introduction of the virus from affected neighbouring countries, and not due to the absence of local vector populations. A key finding has been the substantiation, for the first time, that Culicoides, and particularly the potential vectors C. obsoletus/C. scoticus and C. dewulfi, can be active at night inside livestock buildings and not only outside, as originally believed. The endophagic tendencies of members of the Obsoletus group are discussed in light of the prolonged period of BTV transmission during the autumn of 2006 and the risk of BTV overwintering and resurgence in the spring of 2007. Overall, there is an urgent need to improve our knowledge on the ecology of local Culicoides species before any clear, effective and reliable recommendations can be provided to the veterinary authorities in terms of prevention and control.     

Seasonal dynamics of biting midges (Diptera: Ceratopogonidae: Culicoides), the potential vectors of bluetongue virus, in Sweden

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).     

Rapid diagnostic PCR assays for members of the Culicoides obsoletus and Culicoides pulicaris species complexes, implicated vectors of bluetongue virus in Europe

Biting midges of the Culicoides obsoletus Meigen and Culicoides pulicaris L. species complexes (Diptera: Ceratopogonidae) are increasingly implicated as vectors of bluetongue virus in Palearctic regions. However, predicting epidemiological risk and the spread of disease is hampered because whilst vector competence of Culicoides is expressed only in adult females, morphological identification of constituent species is only readily applicable to adult males and some species distinguishing traits have overlapping character states. Furthermore, adult males are typically rare in field collections, making characterisation of Culicoides communities impossible. Here we highlight the utility of mitochondrial cytochrome oxidase subunit I (COI) DNA sequences for taxonomic resolution and species identification of all species within C. obsoletus and C. pulicarus complexes. Culicoides were collected from 18 sites in the UK and Continental Europe, and identified to species level, or species complex level, based on morphological characters. The sample comprised four species from the C. obsoletus complex (n = 88) and five species from the C. pulicaris complex (n = 39). The DNA sequence of the 5' end of the COI gene was obtained from all individuals. Each member species formed a well-supported reciprocally monophyletic clade in a maximum likelihood phylogeny. Levels of DNA sequence divergence were sufficiently high between species to allow the design of species-specific PCR primers that can be used in PCR for identification of members of the C. pulicaris complex or in a multiplex PCR to identify members of the C. obsoletus complex. This approach provides a valuable diagnostic tool for monitoring species composition in mixed field collections of Culicoides.     

The 2006 outbreak of bluetongue in northern Europe--the entomological perspective

After bluetongue (BT) appeared in northern Europe in August 2006 entomological studies were implemented in all five affected Member States (MSs) to establish which species of Culicoides had acted as vectors. The findings can be summarised as follows: (i) C. imicola the principal southern European/African vector of BTV has not penetrated into northern Europe, (ii) three pools of C. obsoletus/C. scoticus and one of C. dewulfi assayed RT-PCR-positive to BTV-8, (iii) in support of these results it was found that both potential vectors had also high parity rates (approximately 40%) indicating increased longevity favouring BTV virogenesis and transmission, (iv) furthermore, C. obsoletus/C. scoticus and C. dewulfi occurred also widely and abundantly on sheep and cattle holdings across the entire affected region, (v) and during the latter part of the season showed strong endophily readily entering livestock buildings in significant numbers to bite the animals inside (endophagy), (vi) which demonstrates that housing at best offers only limited protection to livestock from Culicoides attacks, (vii) in contrast the potential vector C. pulicaris sensu stricto was restricted geographically, was captured rarely, had a low parity rate (10%) and was exophilic indicating it played no role in the outbreak of BT, (viii) the incrimination of C. dewulfi as a novel vector is significant because it breeds in cattle and horse dung this close association raising its vectorial potential, but (ix) problems with its taxonomy (and that of the Obsoletus and Pulicaris species complexes) illustrates the need for morphological and molecular techniques to become more fully integrated to ensure progress in the accurate identification of vector Culicoides, (x) midge densities (as adjudged by light traps) were generally low indicating northern European Culicoides to have a high vector potential and/or that significant numbers of midges are going undetected because they are biting (and transmitting BTV) during the day when light traps are not effective, and (xi) the sporadic capture of Culicoides in the winter of 2007 invites re-examination of the current definition of a vector-free period. The re-emergence of BT over a wide front in 2007 raises anew questions as to precisely how the virus overwinters and asks also that we scrutinise our monitoring systems in terms of their sensitivity and early warning capability.     

Molecular characterization of Swiss Ceratopogonidae (Diptera) and evaluation of real-time PCR assays for the identification of Culicoides biting midges

Biting midges of the genus Culicoides (Diptera, Ceratopogonidae) are vectors of several viruses of veterinary relevance, and they can cause insect bite hypersensitivity. As the morphological identification of these tiny insects is a difficult task in many cases, alternative approaches are expedient. With the aim to develop real-time PCRs, we determined partial mitochondrial cytochrome oxidase I gene (mt COI) sequences from 380 Culicoides midges representing three regions of Switzerland, namely the Alps, Midland north of the Alps (Atlantic climate), and South of the Alps (Mediterranean climate). The same region was also sequenced from non-biting midges of the genera Atrichopogon, Brachypogon, Dasyhelea, Forcipomyia and Serromyia. A total of 21 Culicoides species were identified by morphology. Sequence variability (haplotypes) was observed in all species. For each of C. grisescens and C. obsoletus, a novel cryptic species was identified. Whereas all individuals of C. grisescens and of the cryptic C. obsoletus species (O2) originated only from Alpine sites, the known C. obsoletus (O1) species was found in all three regions. Further, a sister taxon to C. pulicaris was identified based on the mt COI sequences and named Culicoides sp. Alignments of available mtCOI sequences from Ceratopogonidae (GenBank, this study) were used to design real-time PCR primers and probes to distinguish C. chiopterus, C. deltus, C. dewulfi, C. grisescens (including the cryptic species), C. imicola, C. lupicaris, C. obsoletus O1, C. obsoletus O2, C. pulicaris, C. scoticus and Culicoides sp. Specificities of primers and probes was tested with cloned targets representing 1 to 4 haplotypes of 18 Culicoides spp. and 1 haplotype each from 4 other Ceratopogonidae. No cross-reactivity was observed when plasmid template representing 5 × 10(6) gene copies was tested, but it was evident (Ct values ≤ 30) in few instances when plasmid template representing 5 × 10(9) gene copies was utilized, the latter corresponding to the total gene copy number (as determined in this study) in 20 insects. The sensitivities of two assays (C. imicola, C. grisescens) were tested by spiking single insects into pools of 99 or 999, randomly selected non-target Ceratopogonidae (with approx. 90% Culicoides specimens). In the pools of 100, Ct values were in the range of those obtained with single insects when employing 1% of the isolated DNA, whereas the sensitivity with the pools of 1000 was low, presumably due to the low DNA concentrations obtained with a protocol that seems inadequate for these larger pools. Thus, the assays as described are applicable for the specific identification of biting midges in small pools. Primers and probes of this study were devised to be suitable for multiplexed assays but these evaluations await to be performed.     

Bluetongue virus isolations from midges belonging to the Obsoletus complex (Culicoides, Diptera: Ceratopogonidae) in Italy

Between July and September 2002 there were outbreaks of bluetongue on three sheep holdings in the communities of San Gregorio Magno (Salerno, Campania), Laviano (Salerno, Campania) and Carpino (Foggia, Puglia), and the involvement of bluetongue virus (btv) was confirmed serologically and virologically. The mortality rate was at least 11 per cent and involved btv serotype 2 (btv-2) and serotype 9 (btv-9). These holdings were also surveyed for the Culicoides (Diptera: Ceratopogonidae) vectors; approximately 10,000 midges belonging to 15 species were captured, but they did not include a single specimen of the classical Afro-Asiatic bluetongue vector, Culicoides imicola. Species belonging to the Obsoletus complex dominated the light-trap collections, and Culicoides obsoletus Meigen, Culicoides scoticus Downes and Kettle and Culicoides dewulfi Goetghebuer constituted 90 per cent of all the Culicoides species captured. Fifty-six pools of the Obsoletus complex (excluding C dewulfi), each containing 100 individual midges and containing only parous and gravid females, were assayed for virus. btv-2 was isolated from three pools from San Gregorio Magno and Carpino, and btv-9 was isolated from one pool from Laviano. These results indicate that a species other than C imicola is involved in the current re-emergence of bluetongue in the Mediterranean Basin, but whether it is C obsoletus sensu stricto or C scoticus, or both, is uncertain.     

Culicoides vectors of bluetongue virus in Chester Zoo

On four nights in June 2008, light traps were operated for Culicoides biting midges, the vector species for bluetongue virus (BTV), at five sites in Chester Zoo in north-west England. Over 35,000 Culicoides midges, of 25 species, were captured, including high densities inside animal enclosures. Over 94 per cent of all the Culicoides trapped were females of the Obsoletus group, which is implicated as the vector of BTV serotype 8 in northern Europe. The mean catch of this group per trap per night was over 1500, suggesting a potential risk of BTV transmission if the virus is introduced to Chester Zoo in the animals or midges in the summer.     

Efficacy of Flectron-eartags (cypermethrin) for control of midges (Culicoides) as the vectors of bluetongue virus in cattle: field studies and biossays

When in 2006 infection with bluetongue for the first time occurred in Germany the registered and already against flies and tabanids in cattle proofed Flectron ear tags were used against the blood feeding vector midges (Culicoides) also. However, the efficacy against gnats was not yet proofed. The efficacy of 1 and 2 ear tags (1,067 g cypermethrin per ear tag) per animal was investigated in North Germany with 237 heifers and dairy cows. Midges were caught in suction light traps close to the cattle on pasture or became trapped by mouth operated aspirators directly at the skin of the animal bodies. Within 12,051 specimens of midges 12 species of Culicoides could be identified. On grasslands 3 species, C. obsoletus, C. pulicaris and C. dewulfi were found to be dominant. These 3 species are also known to be vectors of BTV. The toxic efficacy was found for 14 days with 1 ear tag and up to 21 days with 2 ear tags. This duration of efficacy was confirmed in the laboratory with hair clippings from the dorsal line and the ventral abdomen (bioassay). In accordance with workers in the U.S.A. it is concluded that insecticide-impregnated ear tags will reduce the number of biting midges, and by this way the risk of infection with BTV in herds of treated cattle will be reduced as well as in other cattle of a particular region. It is concluded that ear tags are of considerable value as part of an integrated control program for BT, e.g. vaccination.     

Culicoides trapping with Rothamsted suction traps before and during the bluetongue epidemic of 2006 in Belgium

The collection of biting midges was taking place some months before the first bluetongue outbreak in Belgium in August 2006. The Walloon Agricultural Research Centre had been monitoring aphid populations at two sites annually in Belgium (Gembloux and Libramont), using two stationary '12-m' Rothamsted suction traps. For the Gembloux trap, collections of insects captured daily from 11 May 2006 onwards were already available at the time of the outbreak. An examination of these samples revealed the presence of Culicoides, some species of which are considered as potential vectors of the bluetongue virus (BTV). The trapping was therefore extended beyond the normal aphid activity period and the Culicoides captured were identified to species level. From 11 May to 31 December 2006, the Gembloux trap caught 664 Culicoides specimens belonging to 19 species comprising known BTV-vectors. The second trap, at Libramont, was reactivated from 12 September to 13 October and caught 97 specimens belonging to nine species, all of which had been found at the Gembloux site. Among the 19 species identified, four were new to Belgian fauna: Culicoides achrayi, C. deltus, C. lupicaris and C. newsteadi. This paper examines the overall phenology and the physiological status of Culicoides in 2006 before and during the bluetongue epidemic. It discusses the potential of the Rothamsted suction trap to monitor Culicoides.     

Culicoides species attracted to horses with and without insect hypersensitivity

The aims of this study were to determine (1) which species of Culicoides is most commonly attracted to horses, (2) whether horses suffering insect hypersensitivity attract more Culicoides spp. than unaffected horses, and (3) the times when Culicoides spp. are most active. Horses affected by insect hypersensitivity and unaffected horses were placed inside mosquito netting tents for 30 min at different times of the day. All Culicoides spp. trapped inside the tents were collected and identified. C. obsoletus was the most common species found, followed by C. pulicaris. Healthy horses attracted slightly more midges than horses that were affected with insect hypersensitivity. All of the Culicoides species were most active at sunset, less so at sunrise and very few or no midges were trapped in the afternoon or at night.     

Emergence of Culicoides obsoletus from indoor and outdoor breeding sites

Culicoides obsoletus (Diptera: Ceratopogondae) is considered as the probable main vector of Bluetongue virus (BTV) in northern Europe. Its breeding sites are poorly documented at the present time. We report numerous emergences of C. obsoletus s. str. from soil samples collected in two holdings between August and September 2010. Specimens were collected regularly in the laboratory during 80 days. In one holding, 1584 C. obsoletus midges emerged from used litter collected inside a dairy cow building and 211 C. obsoletus midges emerged from manure left outside the farm buildings. In the second holding, the number of emergences observed was much lower, especially for indoor samples. We discuss the impact of the farming practices on the abundance of emergence between both holdings on one side and between indoor and outdoor breeding sites on the other side. The observation of a peak in emergence and high emergence rates recorded in the laboratory for indoor samples let us assume that these breeding sites are of great importance, especially when it comes to understand the biology of this widespread species and its role in the transmission of BTV.     

Intradermal challenge of Icelandic horses with extracts of four species of the genus Culicoides

Twenty-three Icelandic horses were challenged with extracts of four species of biting midges: Culicoides pulicaris, C chiopterus, C obsoletus and C impunctatus. Fourteen of the tested horses were affected with summer eczema. The horses were challenged intradermally with 0.1 ml of whole-body extracts of midges at a concentration of 0.01 or 0.005 per cent weight/volume. The skin reactions were measured after 30 minutes, 60 or 180 minutes and four, 24 and 48 hours after injection. Antigen titration showed that the reaction was dependent on the antigen concentration. Eight of nine unaffected horses failed to respond to any of the four antigens; the remaining animal responding to two of the four antigens. Ten of the 14 affected horses responded to at least three of the four antigens, while two of the animals in this group failed to respond to any. The mean responses to C chiopterus, C obsoletus and C impunctatus, read after 30 minutes, 60 minutes and four hours were significantly higher in the affected horses than in the unaffected horses. A significant difference was also found in the mean response to C chiopterus and C impunctatus, read after 24 hours.     

Distribution and abundance of Bluetongue vectors in Sardinia: comparison of field data with prediction maps

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.     

The phenology and population dynamics of Culicoides spp. in different ecosystems in The Netherlands

The Netherlands has enjoyed a relatively free state of vector-borne diseases of economic importance for more than one century. Emerging infectious diseases may change this situation, threatening the health of humans, domestic livestock and wildlife. In order to be prepared for the potential outbreak of vector-borne diseases, a study was undertaken to investigate the distribution and seasonal dynamics of candidate vectors of infectious diseases with emphasis on bluetongue vectors (Culicoides spp.). The study focused primarily on the relationship between characteristic ecosystems suitable for bluetongue vectors and climate, as well as on the phenology and population dynamics of these vectors. Twelve locations were selected, distributed over four distinct habitats: a wetland area, three riverine systems, four peat land areas and four livestock farms. Culicoides populations were sampled continuously using CO(2)-baited counterflow traps from July 2005 until August 2006, with an interruption from November 2005 to March 2006. All vectors were identified to species level. Meteorological and environmental data were collected at each location. Culicoides species were found in all four different habitat types studied. Wetland areas and peat bogs were rich in Culicoides spp. The taxonomic groups Culicoides obsoletus (Meigen) and Culicoides pulicaris (Linnaeus) were strongly associated with farms. Eighty-eight percent of all Culicoides consisted of the taxon C. obsoletus/Culicoides scoticus. On the livestock farms, 3% of Culicoides existed of the alleged bluetongue vector Culicoides dewulfi Goetghebuer. Culicoides impunctatus Goetghebuer was strongly associated with wetland and peat bog. Many Culicoides species were found until late in the phenological season and their activity was strongly associated with climate throughout the year. High annual variations in population dynamics were observed within the same study areas, which were probably caused by annual variations in environmental conditions. The study demonstrates that candidate vectors of bluetongue virus are present in natural and livestock-farm habitats in the Netherlands, distributed widely across the country. Under favourable climatic conditions, following virus introduction, bluetongue can spread among livestock (cattle, sheep and goats), depending on the nature of the viral serotype. The question now arises whether the virus can survive the winter conditions in north-western Europe and whether measures can be taken that effectively halt further spread of the disease.     

Simultaneous quantification of the relative abundance of species complex members: application to Culicoides obsoletus and Culicoides scoticus (Diptera: Ceratopogonidae), potential vectors of bluetongue virus

The two sympatric sibling species Culicoides obsoletus (Meigen) and Culicoides scoticus Downes and Kettle (Diptera: Ceratopogonidae), are known to be competent vectors for bluetongue virus in the Palaearctic region. However, morphological identification of constituent species is only readily applicable to adult males and these two species distinguishing traits have overlapping character states. As their vector competence may differ in space and time, the correct identification and quantification of specimens of both species are essential for understanding bluetongue epidemiology. However, no molecular tools are available for high-throughput identification of the two species. We therefore developed a quantitative duplex real-time PCR assay to determine the relative abundance of each sibling species in a sample using TaqMan probes. For each species, standard curves were constructed from serial dilutions of purified plasmid DNA containing ITS1-5.8S-ITS2 (rDNA) in the range of 10(-1) to 10(-5)ng/μL. Standard curves were used to quantify samples of mixed C. obsoletus/C. scoticus specimens. Specificity was evaluated with 5156 specimens representing 62 species. Based on the DNA quantities detected according to the standard curves, a quadratic model developed on 1100 males and validated on 555 females was able to predict the relative abundance of each species simultaneously in a one-shot reaction (Pearson coefficient of 0.999). Our assay showed a requirement of two specimens or less for 95% of the predictions, making it highly applicable to field collections. Extensive use of this real-time PCR assay will provide a better understanding of geographical distribution, dynamics, and bionomics on a species level, which is essential for risk assessment. This approach is an important contribution to medical entomology for investigating the vector role of arthropod sibling species.     

Endophily in Culicoides associated with BTV-infected cattle in the province of Limburg, south-eastern Netherlands, 2006

Culicoides were captured at a BTV-infected dairy near Gulpen in the province of Limburg (south-east Netherlands) between 14 September and 4 October 2006. Onderstepoort-type blacklight traps were used to sample Culicoides both inside and outside a partially open shed housing 11 cattle. A total of 28 light trap collections were made at the shed and yielded:

• 9371 Culicoides representing 11 species; >90% comprised five potential vectors of BTV and in order of abundance were Culicoides obsoletus and Culicoides scoticus (of the Obsoletus Complex), Culicoides dewulfi, Culicoides pulicaris and Culicoides chiopterus; Culicoides imicola, the principal Mediterranean (and African) vector of BTV, was absent.

• 2339 Culicoides representing seven species were captured inside (endophily) the cattle shed; >95% comprised the Obsoletus Complex and C. dewulfi. Conversely, the Pulicaris Complex, represented by five species and including C. pulicaris, showed strong exophily with >97% captured outside the shed.

• 7032 Culicoides were captured outside the shed, approximately threefold more than inside. This trend was reversed on an overcast day, when eightfold more Culicoides were captured inside; this indicates that when the light intensity outdoors is low Culicoides will attack (i) earlier in the day while cattle are still at pasture, and (ii) might follow cattle into the sheds in the late afternoon leading to elevated numbers of biting midges being trapped inside the shed during the subsequent hours of darkness.

• Culicoides were captured inside the shed on all 14 sampling nights. On occasion up to 33% were freshly blood fed indicating they had avidly attacked the cattle inside (endophagy); because half the cattle had seroconverted to BTV, and because no cattle were left outdoors at night, the data indicate that (i) the housing of animals in partially open buildings does not interrupt the transmission of BTV, and/or (ii) BTV is being transmitted while cattle are grazing outdoors during the day.

• The capture of partially engorged midges inside the shed shows they are being disturbed while feeding; this may lead to cattle being attacked repeatedly, and if these attacks include older parous BTV-infected Culicoides, may enhance virus dissemination (particularly in sheds where cattle stand close together).

• Endo- and exophagy by potential vector Culicoides – coupled to increased adult longevity and multiple feeding events in single (potentially) infected midges – would ensure an R₀ of >1, resulting in the continued maintenance and spread of BTV within local vertebrate populations.

• Four light trap collections made additionally in a mature deciduous forest 70 m from the shed yielded a high proportion (48%) of gravid females amongst which 10% had incompletely digested blackened blood meals in their abdomens; the absence of this age category in Culicoides captured at the sheds indicates that all Culicoides, after engorgement, exit the buildings to undergo oogenesis elsewhere.

In Europe, the blacklight trap is used widely for the nocturnal monitoring of Culicoides; a drawback to this approach is that this trap cannot be used to sample midges that are active during the day. Because diurnal biting in vector Culicoides may constitute a significant and underestimated component of BTV transmission a novel capture methodology will be required in future and is discussed briefly.     

Endophily in Culicoides associated with BTV-infected cattle in the province of Limburg, south-eastern Netherlands, 2006

Culicoides were captured at a BTV-infected dairy near Gulpen in the province of Limburg (south-east Netherlands) between 14 September and 4 October 2006. Onderstepoort-type blacklight traps were used to sample Culicoides both inside and outside a partially open shed housing 11 cattle. A total of 28 light trap collections were made at the shed and yielded: In Europe, the blacklight trap is used widely for the nocturnal monitoring of Culicoides; a drawback to this approach is that this trap cannot be used to sample midges that are active during the day. Because diurnal biting in vector Culicoides may constitute a significant and underestimated component of BTV transmission a novel capture methodology will be required in future and is discussed briefly.