Bluetongue Vectors Research Articles

Description of breeding sites ofCulicoidesspecies (Diptera: Ceratopogonidae) in Turkey

The aim of this study was to describe the breeding sites of Culicoides species in Konya province, Turkey. The samples taken from 11 different habitats in Konya province were examined for Culicoides species. The collected adult Culicoides specimens were reared in plastic buckets in our laboratory. Among 2,798 specimens reared, 18 species were identified. Culicoides circumscriptus Kieffer, 1918 was the most abundant species reared in the samples taken from mud rich in organic matters near the water reservoirs; C. circumscriptus, C. nubeculosus (Meigen), 1830 and C. shaklawensis Khalaf, 1957 in moist soil with organic matter; C. geigelensis Dzhafarov, 1964 in moist soils, along watering channels and dripping waters; C. festivipennis Kieffer, 1914 and C. circumscriptus along sewage channel; C. festivipennis in reed sites and along garden watering channels; C. circumscriptus in rain pools; C. odiatus Austen, 1921 and C. circumscriptus in mud near the dams; C. geigelensis and C. kibunensis Tokunaga, 1937 from sites along the stream. No Culicoides was reared in the samples obtained from livestock dung and tree holes. It was observed that C. circumscriptus, C. festivipennis and C. shaklawensis preferred mud rich in organic matters near the water reservoirs. Culicoides imicola Kieffer, 1913, which is the main vector of bluetongue, was not detected in Konya province. The others vectors of bluetongue, C. obsoletus gr. (Meigen), 1818, C. schultzei gr. (Enderlein), 1908 and C. pulicaris (Linnaeus), 1758 were only obtained in little numbers.

Opinion of the Scientific Panel on Animal Health and Welfare (AHAW) on request from the Commission on bluetongue vectors and vaccines

Opinion of the Scientific Panel on Animal Health and Welfare (AHAW) on request from the Commission on bluetongue vectors and vaccines

Establishment of an early warning system against Bluetongue virus in Switzerland

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.

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.

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 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),...

Phylogenetic relationships of the subgenus Avaritia Fox, 1955 including Culicoides obsoletus (Diptera, Ceratopogonidae) in Italy based on internal transcribed spacer 2 ribosomal DNA sequences

Abstract. Biting midges of the genus Culicoides include vector species for orbiviral diseases, such as bluetongue and African horse sickness. Although the Afro‐Asiatic species C. imicola is the major vector of bluetongue in the Mediterranean basin, recent outbreaks in regions where C. imicola is absent has incriminated other Culicoides, including those belonging to the Obsoletus Complex of the subgenus Avaritia Fox, 1955. The classical taxonomy of this species complex is unclear and this stimulated the molecular analysis of twenty Culicoides populations sampled from eighteen localities across Italy. Ribosomal internal transcribed spacer 2 sequences were used to characterize the intra‐ and interspecific variation between Italian members of the Obsoletus Complex and related species, by means of an analysis of molecular variance and phylogenetic analyses. Although morphological differentiation is often extremely difficult, the molecular analysis clearly demonstrated a high degree of divergence between most species. The study showed that at least seven species of the subgenus Avaritia occur in Italy; these are C. obsoletus, C. scoticus, C. montanus, C. dewulfi, C. imicola and two species that could not be identified with certainty, but one of which is similar to C. chiopterus. Finally, a simple polymerase chain reaction assay was developed that rapidly discriminates between four members of the Obsoletus Complex in Italy, a prerequisite for vector identification.

Phylogenetic status and matrilineal structure of the biting midge, Culicoides imicola, in Portugal, Rhodes and Israel.

The biting midge Culicoides imicola Kieffer (Diptera: Ceratopogonidae) is the most important Old World vector of African horse sickness (AHS) and bluetongue (BT). Recent increases of BT incidence in the Mediterranean basin are attributed to its increased abundance and distribution. The phylogenetic status and genetic structure of C. imicola in this region are unknown, despite the importance of these aspects for BT epidemiology in the North American BT vector. In this study, analyses of partial mitochondrial cytochrome oxidase subunit I gene (COI) sequences were used to infer phylogenetic relationships among 50 C. imicola from Portugal, Rhodes, Israel, and South Africa and four other species of the Imicola Complex from southern Africa, and to estimate levels of matrilineal subdivision in C. imicola between Portugal and Israel. Eleven haplotypes were detected in C. imicola, and these formed one well-supported clade in maximum likelihood and Bayesian trees implying that the C. imicola samples comprise one phylogenetic species. Molecular variance was distributed mainly between Portugal and Israel, with no haplotypes shared between these countries, suggesting that female-mediated gene flow at this scale has been either limited or non-existent. Our results provide phylogenetic evidence that C. imicola in the study areas are potentially competent AHS and BT vectors. The geographical structure of the C. imicola COI haplotypes was concordant with that of BT virus serotypes in recent BT outbreaks in the Mediterranean basin, suggesting that population subdivision in its vector can impose spatial constraints on BT virus transmission.

Prediction of bluetongue vector distribution in Europe and north Africa using satellite imagery

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.

Presence in the Balearic Islands (Spain) of the midges Culicoides imicola and Culicoides obsoletus group.

An outbreak of the livestock viral disease bluetongue (BT) was detected during September and October 2000 in the Balearic Islands, Spain. Due to the lack of information about the species of Culicoides (Diptera: Ceratopogonidae) reported in the affected area, six farms in Majorca, four in Minorca and one in Ibiza were selected to carry out surveillance of Culicoides adults using light traps. Here, for the first time, we report the presence in the Balearic Islands of Culicoides imicola Keiffer, the main vector of BT, and the Culicoides obsoletus Meigen group.

Air streams and the introduction of animal diseases borne on Culicoides (Diptera, Ceratopogonidae) into Israel.

The role of air streams and climatic conditions in the transport of biting midges (Culicoides spp.), the vectors of bluetongue and Akabane viruses, is known from other parts of the world. Knowledge of such climatic systems may enable predictions to be made on the occurrence of these diseases and may also assist in drawing up vaccination and control programmes. In this study, data on temperature, relative humidity, wind speed and direction have been analysed for the years 1964, 1966, 1969 and 1988, at altitudes of 0.5 km, 1 km and 1.5 km. The authors examine the relationship between these parameters and outbreaks of bluetongue and Akabane. The results show that outbreaks of bluetongue and most seroconversions did not occur before the season of the Persian trough air-stream system. This was despite the fact that the vector C. imicola was present in March and April, i.e. before this air-stream system began. Circumstantial evidence to indicate the introduction of infected midges by wind is stronger than the evidence against such an introduction. In addition, the amount of precipitation in the spring seasons of 1968 to 1986 could not be positively correlated to the number of bluetongue outbreaks. These results indicate that cooperation among the countries in the region of the Persian trough air system could provide an early warning system against wind-borne infected vectors. An outbreak of bluetongue in one country would be a warning to the next country along this route.

Culicoides (Diptera: Ceratopogonidae) Collected During Epizootics of Hemorrhagic Disease among Captive White-tailed Deer

To help determine specific vectors of epizootic hemorrhagic disease (EHD) and bluetongue (BT) viruses for white-tailed deer, Odocoileus virginianus Zimmermann, in the southeastern United States, Culicoides sp. midges were collected during epizootics of hemorrhagic disease among captive white-tailed deer in Georgia, Mississippi, and North Carolina. Culicoides variipennis (Coquillett), a confirmed vector of EHD and BT viruses, was present in low numbers in light-trap collections made at all sites. Collections from deer made in Georgia and North Carolina yielded only a single specimen of C. variipennis. Other Culicoides species present in far greater numbers during the epizootics included C. lahillei Lutz, C. paraensis (Goeldi), and C. stellifer (Coquillett) C. lahillei warrants particular attention as a potential vector because its readily feeds on white-tailed deer and was by far the predominant species collected from deer during the epizootics.

Apyrase activity and adenosine diphosphate induced platelet aggregation inhibition by the salivary gland proteins of Culicoides variipennis, the North American vector of bluetongue viruses

Salivary gland homogenates of Culicoides variipennis, the primary vector of bluetongue (BLU) viruses in North America, were analyzed for apyrase activity. Apyrase (ATP diphosphohyrolase, EC 3.6.1.5) is an anti-hemostatic and anti-inflammatory salivary enzyme of most hematophagous arthropods. The enzyme activity was measured by the release of orthophosphate using ATP, ADP, and AMP as substrates with Ca 2+ as the divalent cation. ATPase (11.5 ± 1 mU/pair of glands), ADPase (7.3 ± 0.7 mU/pair of glands), and insignificant ( P < 0.05) AMPase (0.07 mU/pair of glands) activities were detected in female salivary glands. Male salivary glands contained lower amounts of ATPase and ADPase activated by Mg 2+. Molecular and ADPase activities were greatest at pH 8.5, and were similarly activatedby Mg 2+. Molecular sieving HPLC of salivary gland homogenates generated a single peak which coincided with ATPase and ADPase, but no AMPase, activity; the protein has an estimated molecular mass of 35 000 Da. ATPase and ADPase activity, and total protein concentration, were reduced ( P < 0.05) in the salivary glands of females after taking a blood meal from a sheep. Salivary gland homogenates also inhibited ADP-induced platelet aggregation in vitro. It is concluded that the salivary ATPase and ADPase activities of C. variipennis reside in one enzyme, and that this enzyme is likely an apyrase. The apyrase activity is thought to be responsible for the inhibition of ADP-induced platelet aggregation, as indicated by the apparent discharge of apyrase from salivary glands into the host during blood feeding. This suggests that apyrase is one of the salivary proteins present in C. variipennis acting as antigens in the development of Colicoides hypersensitivity in ruminants and horses. Apyrase may inhibit an inflammatory response at the feeding site through the subsequent degradation of its end-product, AMP, to adenosine, a potent anti-inflammatory substance, by the ecto-5′ nucleotidase activity of neutrophils.

Culicoides vectors of bluetongue and African horse sickness viruses in Mauritius.

Culicoides vectors of bluetongue and African horse sickness viruses in Mauritius.

Parity and Voltinism of Several Culicoides spp. (Diptera: Ceratopogonidae) in Israel, as Determined by Two Trapping Methods

Numbers of nulliparous and parous females of several species of Culicoides were studied through the flight season at Bet-Dagan, Israel, by means of suction traps and light traps. Traps were placed in various situations inside a calf shed and at low and high levels in a nearby tree. Voltinism in these species was determined on the basis of numbers of nulliparous females, supported by the peaks in the male populations. In Culicoides circumscriptus Kieffer, an ornithophilic species, more were caught at 26 m than at the base of the tree or in the calf shed. C. distinctipennis Austen, another ornithophilic species, preferred the enclosure (i.e., calf shed) to the tree despite the presence of birds at both sites. The putative bird feeders C. cataneii Clastrier, C. saevanicus Dzhafarov, and C. univittatus Vimmer were caught only in tree traps. The mammalian feeders C. imicola Kieffer and C. oxystoma Kieffer were more abundant in the calf shed than in the tree. Monks Wood traps equipped with blacklights were found to be equally attractive for nulliparous and parous female C. imicola, C. newsteadi Austen, C. obsoletus Meigen, and C. oxystoma. Catches of male and nulliparous female C. distinctipennis, C. imicola, and C. oxystoma were not affected by moon phase. C. imicola, the principal bluetongue vector in Israel, underwent 11 generations during the year, 8 in July–December (the bluetongue season). C. oxystoma, which ranks third as a potential vector of bluetongue, was present and completed five generations, mainly between August and December. C. distinctipennis underwent four generations between September and December.

Preliminary studies on the [formula omitted] spp. as potential vectors of bluetongue in the Caribbean region

Ten species of Culicoides , namely C. pusillus, C. furens, C. foxi, C. jamaicensis, C. phlebotomus, C. trilineatus, C. borinqueni, C. paraensis and C. hoffmani were collected by light trap near livestock in Puerto Rico, St. Croix, and Barbados. Culicoides insignis and C. pusillus were the most numerous species collected, were collected from all three islands, and were at their peak populations during the time that most sentinel calves seroconverted to bluetongue virus in Puerto Rico. Therefore, they must be considered prime candidates as vectors of bluetongue virus in the region.

Potential vectors of bluetongue in Lesbos, Greece.

Potential vectors of bluetongue in Lesbos, Greece.

The susceptibility of the sandfly Lutzomyia longipalpis (Lutz & Neiva), diptera, phlebotomidae, to laboratory infection with bluetongue virus.

Bluetongue virus multiplied in the sandfly Lutzomyia longipalpis after intrathoracic inoculation but not after oral ingestion of virus. The level of virus multiplication was lower than that observed in similar experiments with the North American vector of bluetongue, Culicoides variipennis. Inoculated sandflies did not transmit virus after 6 to 9 days incubation at 25 degrees C. It is unlikely that L. longipalpis would be important in the maintenance of bluetongue virus in the wild.

Biology and Bionomics of Bloodsucking Ceratopogonids

In recent years there has been increasing attention paid to three genera [Culicoides, Leptoconops, Forcipomyia (Lasiohelea)] of ceratopogonids, whose females feed on warm-blooded vertebrates. This habit makes them pests of man and livestock. They are a nuisance to humans living on the coast and in poorly drained inland areas, but they are most important as vectors of virus diseases that are transmitted to domestic animals. Culicoides are proven vectors of bluetongue to sheep and cattle (93) and have been incriminated in the transmission of horse sickness to equines and ephemeral fever to cattle (26). The involvement of bloodsucking ceratopogonids in the transmission of human and animal diseases was reviewed in 1965 (60) and their bionomics and control in 1962 (59) and 1969 (61). The present review refers only to work covered in the latter two articles where necessary for the appreciation of more recent research. Current interest in ceratopogonids has been fostered by a biannual news letter, Ceratopogonid Information Exchange, edited by J. Boorman, Animal Virus Research Institute, Pirbright, Woking, Surrey, U.K.

Blood feeding of Culicoides (Diptera, Ceratopogonidae) in Kenya in relation to the epidemiology of bluetongue and ephemeral fever

AbstractEngorged Culicoides specimens were collected in light-traps from 16 sites in Kenya. The precipitin test was used to identify the blood-meal source of 682 specimens of 21 species over a period of five years. Culicoides pallidipennis C, I. &amp; M. and C. schultzei (End.) were shown to feed mainly on cattle and to a lesser extent on sheep, and thus could be involved in the transmission of bluetongue virus. C. cornutus De Meillon, C. milnei Aust. and C. zuluensis De Meillon are probably not common enough as feeders on cattle and sheep to play more than an incidental role as vectors of bluetongue. C. schultzei is probably also important in the transmission of ephemeral fever. No groups of vertebrates other than Bovidae were implicated as virus reservoirs.