Influence of light and kairomone baiting systems on trap collections of biting midges in southern Sweden.

Effective surveillance is essential for protecting livestock from Culicoides biting midges and the viruses they transmit. The objective of this study was to determine how the baiting system used in traps (UV, incandescent light, incandescent light with CO2 , and incandescent light with CO2 and 1-octen-3-ol) influences estimates of midge population abundance, parity, and diel activity. This was achieved through a standardized trapping protocol conducted in three habitats in Sweden. UV light traps caught the most Culicoides species and more C. obsoletus complex females than incandescent light traps. Traps baited with CO2 plus 1-octen-3-ol caught more female C. impunctatus than incandescent light traps. No consistent effect of bait type was found on C. obsoletus parity rate, as estimated from the proportion of midges with presence or absence of pigmentation. Midge activity, as reflected by trap catches, peaked between -3 h and +3 h relative to sunset, with UV traps catching significantly more female C. obsoletus complex and C. impunctatus at and after sunset than before sunset. We conclude that baiting system can influence biting midge collections, even using identical traps. Effective surveillance may require more than one bait type and kairomones to attract species that do not feed exclusively on cattle.

Effects of ultraviolet LED versus incandescent bulb and carbon dioxide for sampling abundance and diversity of Culicoides in Florida.

Biting midges (Ceratopogonidae: Culicoides) are vectors of bluetongue virus and epizootic hemorrhagic disease virus which cause significant morbidity and mortality in ruminants. Recently, ultraviolet light emitting diodes (UV/LEDs) in conjunction with suction traps have been widely utilized for Culicoides spp. collections. Despite the use of these traps, limited work has been done comparing sampling variability associated with these light types with and without CO2. For this objective, mini-CDC light traps with four different attractant combinations were operated at eight sites across Florida between April and October 2017. Trap attractants included white-incandescent lights and UV/LEDs with and without CO2 to determine optimum combinations of light type and attractant for species richness, diversity, and abundance of Culicoides spp. in Florida. The results of the study demonstrate that traps with UV/LED light collect greater richness, diversity, and abundance of Culicoides species than traps with white-incandescent light. Addition of CO2 resulted in greater diversity in traps with UV/LED lights, but lower diversity in traps with white-incandescent light. Therefore, CO2 may be used to increase the abundance of Culicoides spp. collected by traps, regardless of light type, but the ability for CO2 to attract a higher number and diversity of species to traps varies by the light type used. Therefore, we suggest using CO2 primarily in conjunction with UV/LED light. When CO2 is not available, UV/LED light used alone can be substituted without a significant loss in species richness or diversity, although abundance of most Culicoides species will be significantly lower in the absence of CO2.

Comparison of different light sources for trapping Culicoides biting midges, mosquitoes and other dipterans.

The response of Culicoides biting midges, mosquitoes and other dipterans to different wavelengths was evaluated in a farm meadow in northern Spain. A total of 9449 specimens of 23 species of Culicoides, 5495 other ceratopogonids (non-biting midges), 602 culicids and 12428 other mixed dipterans were captured. Centers for Disease Control and Prevention (CDC) suction light traps fitted with five light emitting diodes (LEDs) (white, green, red, blue, ultraviolet) were run for 15 consecutive nights. Significantly more Culicoides were collected in those traps fitted with green, blue or ultraviolet (UV) lights than in red and white-baited LED traps for the most abundant species captured: C. punctatus (37.5%), C. cataneii (26.5%) and C. obsoletus/C. scoticus (20.4%). Similar results were obtained for non-Culicoides ceratopogonids, mosquitoes and other mixed dipterans. Wavelengths in green (570nm) resulted effective for targeting some Culicoides species, culicids and other midges. In a second trial, the effectiveness of 4-W white and UV tubes was compared to traps fitted with UV LED and a standard incandescent light bulb. More specimens of all taxa were collected with fluorescent black light (UV) traps than with the other light sources, except culicids, which were recovered in high numbers from fluorescent white light traps.

Trap placement and attractant choice affect capture and create sex and parity biases in collections of the biting midge, Culicoides sonorensis.

Culicoides sonorensis Wirth & Jones (Diptera: Ceratopogonidae) is the primary North American vector of bluetongue virus (BTV), which can cause high morbidity and mortality in ruminant livestock or wildlife. Worldwide, most Culicoides surveillance relies on light (usually UV) traps typically placed near animals or larval development sites. However, the trapping method can cause sex, species and parity biases in collections. We collected C. sonorensis from three dairies in California using suction traps baited with CO2 , UV light or CO2 + UV placed near animals, wastewater ponds, or in fields. Higher numbers of parous females were collected using CO2 + UV traps, although this difference was only significant on one dairy. UV traps were poor at collecting nulliparous females, but the addition of UV to a trap increased the abundance of males in a collection. Traps set in open fields collected significantly higher numbers of males and females than in either of the other two locations. In some cases, there was a significant interaction between the trap type and site. We discuss the limitations of traditional trapping methodologies for C. sonorensis and make suggestions for vector surveillance.

A comparison of commercial light-emitting diode baited suction traps for surveillance of Culicoides in northern Europe.

BACKGROUND: The response of Culicoides biting midges (Diptera: Ceratopogonidae) to artificial light sources has led to the use of light-suction traps in surveillance programmes. Recent integration of light emitting diodes (LED) in traps improves flexibility in trapping through reduced power requirements and also allows the wavelength of light used for trapping to be customized. This study investigates the responses of Culicoides to LED light-suction traps emitting different wavelengths of light to make recommendations for use in surveillance. METHODS: The abundance and diversity of Culicoides collected using commercially available traps fitted with Light Emitting Diode (LED) platforms emitting ultraviolet (UV) (390 nm wavelength), blue (430 nm), green (570 nm), yellow (590 nm), red (660 nm) or white light (425 nm - 750 nm with peaks at 450 nm and 580 nm) were compared. A Centre for Disease Control (CDC) UV light-suction trap was also included within the experimental design which was fitted with a 4 watt UV tube (320-420 nm). Generalised linear models with negative binomial error structure and log-link function were used to compare trap abundance according to LED colour, meteorological conditions and seasonality. RESULTS: The experiment was conducted over 49 nights with 42,766 Culicoides caught in 329 collections. Culicoides obsoletus Meigen and Culicoides scoticus Downes and Kettle responded indiscriminately to all wavelengths of LED used with the exception of red which was significantly less attractive. In contrast, Culicoides dewulfi Goetghebuer and Culicoides pulicaris Linnaeus were found in significantly greater numbers in the green LED trap than in the UV LED trap. The LED traps collected significantly fewer Culicoides than the standard CDC UV light-suction trap. CONCLUSIONS: Catches of Culicoides were reduced in LED traps when compared to the standard CDC UV trap, however, their reduced power requirement and small size fulfils a requirement for trapping in logistically challenging areas or where many traps are deployed at a single site. Future work should combine light wavelengths to improve trapping sensitivity and potentially enable direct comparisons with collections from hosts, although this may ultimately require different forms of baits to be developed.

The range of attraction for light traps catching Culicoides biting midges (Diptera: Ceratopogonidae).

BACKGROUND: Culicoides are vectors of e.g. bluetongue virus and Schmallenberg virus in northern Europe. Light trapping is an important tool for detecting the presence and quantifying the abundance of vectors in the field. Until now, few studies have investigated the range of attraction of light traps. METHODS: Here we test a previously described mathematical model (Model I) and two novel models for the attraction of vectors to light traps (Model II and III). In Model I, Culicoides fly to the nearest trap from within a fixed range of attraction. In Model II Culicoides fly towards areas with greater light intensity, and in Model III Culicoides evaluate light sources in the field of view and fly towards the strongest. Model II and III incorporated the directionally dependent light field created around light traps with fluorescent light tubes. All three models were fitted to light trap collections obtained from two novel experimental setups in the field where traps were placed in different configurations. RESULTS: Results showed that overlapping ranges of attraction of neighboring traps extended the shared range of attraction. Model I did not fit data from any of the experimental setups. Model II could only fit data from one of the setups, while Model III fitted data from both experimental setups. CONCLUSIONS: The model with the best fit, Model III, indicates that Culicoides continuously evaluate the light source direction and intensity. The maximum range of attraction of a single 4W CDC light trap was estimated to be approximately 15.25 meters. The attraction towards light traps is different from the attraction to host animals and thus light trap catches may not represent the vector species and numbers attracted to hosts.

Quantifying the spatial dependence of Culicoides midge samples collected by Onderstepoort-type blacklight traps: an experimental approach to infer the range of attraction of light traps.

The emergence of bluetongue disease in Europe has led several countries to rapidly establish large-scale entomological surveys of its vectors, which are midges belonging to the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae). These surveys have largely been based on the use of Onderstepoort-type blacklight traps. However, the range of attraction of the traps and the spatial dependence of the samples they provide are unknown, which somewhat complicates subsequent analyses. This paper investigates spatial interaction between Onderstepoort-type blacklight traps based on catches at a central trap placed close to two traps set in consecutive on/off modes. The spatial interaction is inferred from the drop in the number of midges collected in the central trap when nearby traps positioned at 50 m, 100 m or 200 m are turned on. The results showed a significant spatial interaction between traps separated by 50 m for female Culicoides obsoletus/Culicoides scoticus and Culicoides dewulfi. No significant interaction was found for female Culicoides of other species, for male Culicoides, or for traps spaced at ≥100 m. Based on the experimental design geometry and on simple assumptions on the distribution of Culicoides midges in the neighbourhood of the traps, the paper also presents a method to infer the range of attraction of the traps.

The influence of host number on the attraction of biting midges, Culicoides spp., to light traps.

A preliminary study was undertaken to investigate how the number of sheep below a light-suction trap affects the number of female Culicoides obsoletus Meigen (Diptera: Ceratopogonidae) caught. As the number of sheep increased from zero to three, the number of midges caught increased, but there appeared to be no further increase when six sheep were used. The lack of increase between three and six sheep is attributable to different activity rates on certain nights, perhaps in response to weather, and suggests, therefore, that catches in light traps increase linearly with sheep numbers, at least for small host numbers.

Response of biting midges (Diptera: Ceratopogonidae) to carbon dioxide, octenol, and light in southeastern Queensland, Australia.

The effect of 1-octen-3-ol (octenol) on catches of estuarine biting midges in encephalitis vector surveillance (EVS) traps was examined in southeastern Queensland. Octenol by itself was not attractive but appeared to act as a synergist with CO2 to increase catches of most species. For four of six species tested, a medium (about 6 mg/h) release rate of octenol captured the most individuals. Addition of light also increased the catch size of most species. Octenol in combination with CO2 could be used to enhance biting midge catch size, improving the sensitivity of surveillance for midges and the pathogens they vector.

Effect of light trap height on catch of Culicoides (Diptera: Ceratopogonidae) in Israel.

Vertical suction light trapping was conducted in 1981 at two dairy farms, Bet Dagan (traps at 1.4 and 26 m above ground) and Bet Alfa (traps at 1.5 and 20 m). Of the nine Culicoides species caught in both localities, only C. circumscriptus Kieffer and C. cataneii Clastrier showed a significant difference in abundance related to trap height; C. imicola Kieffer and C. schultzei sp. gp. also demonstrated a height preference, but catch sizes did not differ statistically. C. circumscriptus and C. cataneii, both avian feeders, and C. imicola, a mammalian feeder, were caught in greater numbers in the higher than in the lower traps. In contrast, more C. schultzei sp. gp. females were caught in lower than higher traps. Species collected more frequently in higher traps may be more prone to carriage for long distances by air currents and therefore are more likely to be important as dispersal vectors.