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

Sampling of Culicoides with nontraditional methods provides unusual species composition and new records for southern Spain

BACKGROUND

Culicoides midges have been well-studied in Spain, particularly over the last 20 years, mainly because of their role as vectors of arboviral diseases that affect livestock. Most studies on Culicoides are conducted using suction light traps in farmed environments, but studies employing alternative trapping techniques or focusing on natural habitats are scarce.

METHODS

In the present study, we analyze Culicoides captured in 2023 at 476 sites in western Andalusia (southern Spain) using carbon dioxide-baited Biogents (BG)-sentinel traps across different ecosystems.

RESULTS

We collected 3,084 Culicoides midges (3060 females and 24 males) belonging to 23 species, including the new species Culicoides grandifovea sp. nov. and the first record of Culicoides pseudolangeroni for Europe. Both species were described with morphological and molecular methods and detailed data on spatial distribution was also recorded. The new species showed close phylogenetic relations with sequences from an unidentified Culicoides from Morocco (92.6% similarity) and with Culicoides kurensis. Culicoides imicola was the most abundant species (17.4%), followed by Culicoides grandifovea sp. nov. (14.6%) and Culicoides kurensis (11.9%). Interestingly, Culicoides montanus was the only species of the obsoletus and pulicaris species complexes captured, representing the first record of this species in southern Spain. A total of 53 valid Culicoides species have been reported in the area, with 48 already reported in literature records and 5 more added in the present study. Information on the flight period for the most common Culicoides species is also provided.

CONCLUSIONS

To the best of our knowledge, our study represents the most comprehensive effort ever done on nonfarmland habitats using carbon-dioxide baited suction traps for collecting Culicoides. Our data suggests that using carbon dioxide traps offers a completely different perspective on Culicoides communities compared with routinely used light traps, including the discovery of previously unrecorded species.

Field evaluation of newly developed 3D-printed ultraviolet and green light-emitting diode traps for the collection of Culicoides species in Thailand

Culcioides biting midges (Diptera: Ceratopogonidae) are vectors of various veterinary pathogens. Suction light traps are one of the most widely used tools for vector surveillance. The present aim was to compare the efficiency for the collection of Culicoides species between newly developed 3D-printed ultraviolet (Mahidol University (MU) UV LED) and green light-emitting diode (Mahidol University (MU) Green LED) traps baited with CO2 and UV LED Center for Disease Control (CDC) light trap (BioQuip 2770) baited with CO2. The experiment consisted of two replicates of a 3 × 3 Latin square design in each three sampling locations (Location 1, 2, 3 and 4, 5, 6), for 12 nights between 26th July and 7th August 2020 in Thailand. Results showed that efficiency of the MU UV LED light trap was equivalent to that of the BioQuip 2770 trap for the collection of Culicoides. Meanwhile, the efficiency of the MU Green LED light trap was lower than that of both UV LED light traps. In the analysis of Culicoides species composition and sex-age grading, a similar pattern was observed among three light traps except for Culicoides actoni Smith. The newly developed 3D-printed UV LED light trap demonstrated the following advantages over the commercial light trap: cost saving to obtain multiple units, ease of customization and standardization, and increased availability by end-users. Although further assessments in different environmental conditions are needed, this 3D-printed light trap design could minimize the constrains in vector surveillance programs worldwide.

Color preference of Sergentomyia minuta (Diptera: Phlebotominae) determined using Flebocollect Do It Yourself light traps based on LED technology

Whether phlebotomine sand flies show a preference for different light colors remains controversial. As light-capture methods are widely used to study sand flies, knowing the visual stimuli they respond to could help the design of novel control tools to prevent their attraction to hosts. We have detected a significant preference of male Sergentomyia minuta for green and red light sources. Accordingly, male S. minuta were 2.16 and 2.01 times more likely to be lured by Flebocollect model traps with green and red diode-lights, respectively, than the commercial CDC traps. Flebocollect traps are homemade light traps developed through citizen science. Dipterans are widely considered unable to distinguish the color red so this finding was unexpected. To our knowledge, this is the first description of a color preference in a species of the genus Sergentomyia. Our research also confirms the great potential of Flebocollect light traps for use in medical entomology studies.

Comparison of surveillance trapping methods to monitor Culicoides biting midge activity in Trinidad, West Indies

Culicoides biting midges (Diptera: Ceratopogonidae) are biting nuisances and arbovirus vectors of both public health and veterinary significance in Trinidad. We compared sampling methods to define the behaviour and bionomics of adult Culicoides populations at a commercial dairy goat farm. Three static trap designs were compared: (a) Centre for Disease Control (CDC) downdraft UV trap; (b) CDC trap with an incandescent bulb and (c) CDC trap with semiochemical lure consisting of R-(-)-1-octen-3-ol and CO₂ (no bulb). Sweep netting was used to define diel periodicity. A total of 30,701 biting midges were collected using static traps, dominated by female Culicoides furens (>70% of trap collections across all three designs). There was no significant difference in the Margalef's index between the three traps; however, trap designs A and C collected a significantly greater number of individuals than trap B, and trap C gained highest species richness. The greatest species richness and abundance of Culicoides collected by sweep net was observed between 6:00 and 6:15 pm and notable differences in the crepuscular activity pattern of several species were identified. Comparative data on Culicoides species richness, abundance, sex and reproductive status is discussed and can be used to improve surveillance strategies, research designs and risk management.

The Effects of Light Wavelength and Trapping Habitat on Surveillance of Culicoides Biting Midges (Diptera: Ceratopogonidae) in Alabama

In the southeastern United States, biting midges transmit agents of hemorrhagic diseases that are enzootic among white-tailed deer (Odocoileus virginianus (Zimmermann), Artiodactyla: Cervidae). Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae), the only confirmed vector of epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) in the United States, is rarely collected in the Southeast, implying that other Culicoides Latreille species act as vectors. Despite multiple surveillance studies, the influence of trapping habitat and light wavelength on Culicoides sampling has yet to be investigated in Alabama. This study sampled Culicoides species at a deer research facility using CO2-baited CDC light traps with three distinct wavelengths. Traps were rotated within three habitats to examine impacts of habitat type and light wavelength on Culicoides abundance and parity status. For most species, midges were more abundant in a pine forest compared to a hardwood-forest riparian zone or a lightly wooded area adjacent to a seasonal pond. The pine forest generally had negative effects on parity status, suggesting that most females in this habitat were foraging for their first bloodmeal. Ultraviolet (UV) black-light (350 nm-360 nm) attracted more midges than incandescent light or UV LED light (385 nm-395 nm), but wavelength had less of an effect on parity than habitat. This study indicates that light wavelength and habitat significantly influence Culicoides sampling outcomes, and that when collecting parous females is desired (e.g., EHDV/BTV surveillance), targeting areas around oviposition sites may be a better strategy than trapping where midges are most abundant.

Preliminary Study on Comparative Efficacy of Four Light Sources for Trapping Culicoides spp. (Diptera: Ceratopogonidae) in Prachuap Khiri Khan Province, Thailand

The light trap is an important tool to determine the presence and abundance of vectors in the field. However, no one has studied the efficiency of light traps for collecting Culicoides in Thailand. In the present study, the efficacy of four light sources was evaluated in Prachuap Khiri Khan province, Thailand. Incandescent (INCND) light, white fluorescent (WHT-FLR) light, ultraviolet fluorescent (UV-FLR) light, and UV light-emitting diode (UV-LED) light were tested using commercial traps. In total, 30,866 individuals of Culicoides species were collected from November 2020 to June 2021, of which 21,016 were trapped on site 1 and 6,731 were trapped on site 2. The two most abundant Culicoides species were C. imicola (54%) and C. oxystoma (31.2%). UV-FLR was highly effective, followed by UV-LED light, WHT-FLR light, and INCND light, respectively, for Culicoides collection. Significantly, more Culicoides species were collected in those traps baited with UV-FLR light, UV-LED light, or WHT-FLR light than for INCND light traps. Traps equipped with UV-FLR lights can be recommended to trap Culcoides biting midges for monitoring purposes.

UV Light-Emitting-Diode Traps for Collecting Nocturnal Biting Mosquitoes in Urban Bangkok

Simple Summary

This study was conducted to evaluate the efficacy of six ultraviolet light-emitting diodes (UV-LED) traps and a fluorescent light trap for sampling urban nocturnal mosquitoes. Results demonstrated that the fluorescent light trap outperformed all the UV-LED traps throughout the 72 sampling nights and between wet and dry seasons. Among the UV-LED traps, the LED375 trapped the highest number of mosquitoes. Additional field trials are needed to validate these findings in different ecological settings.

Abstract

Well-designed surveillance systems are required to facilitate a control program for vector-borne diseases. Light traps have long been used to sample large numbers of insect species and are regarded as one of the standard choices for baseline insect surveys. The objective of this study was to evaluate the efficacy of six ultraviolet light-emitting diodes and one fluorescent light for trapping urban nocturnal mosquito species within the Kasetsart University (KU), Bangkok. Ultraviolet light-emitting diodes (UV-LEDs), (LED365, LED375, LED385, LED395, and LED405) and a fluorescent light were randomly assigned to six different locations around the campus in a Latin square design. The traps were operated continuously from 18:00 h to 06:00 h throughout the night. The traps were rotated between six locations for 72 collection-nights during the dry and wet seasons. In total, 6929 adult mosquitoes were caught, with the most predominant genus being Culex, followed by Aedes, Anopheles, Armigeres and Mansonia. Among the Culex species, Culex quinquefasciatus (n = 5121: 73.9%) was the most abundant followed by Culex gelidus (n = 1134: 16.4%) and Culex vishnui (n = 21: 0.3%). Small numbers of Aedes, Armigeres, and Anopheles mosquitoes were trapped [Aedes albopictus (n = 219: 3.2%), Aedes pocilius (n = 137: 2.0%), Armigeres subalbatus (n = 97: 1.4%), Anopheles vagus (n = 70: 1.0%), Aedes aegypti (n = 23: 0.3%)]. There were 2582 specimens (37.2%) captured in fluorescent light traps, whereas 942 (13.6%), 934 (13.5%), 854 (12.3%), 820 (11.8%), and 797 (11.5%) were captured in the LED375, LED405, LED395, LED365, and LED385 traps, respectively. None of the UV-LED light traps were as efficacious for sampling nocturnal mosquito species as the fluorescent light trap. Among the five UV-LED light sources, LED375 trapped the greatest number of mosquitoes. Additional field trials are needed to validate these findings in different settings in order to substantially assess the potential of the LEDs to trap outdoor nocturnal mosquitoes.

Postharvest Ultraviolet Radiation in Fruit and Vegetables: Applications and Factors Modulating Its Efficacy on Bioactive Compounds and Microbial Growth

Ultraviolet (UV) radiation has been considered a deleterious agent that living organisms must avoid. However, many of the acclimation changes elicited by UV induce a wide range of positive effects in plant physiology through the elicitation of secondary antioxidant metabolites and natural defenses. Therefore, this fact has changed the original UV conception as a germicide and potentially damaging agent, leading to the concept that it is worthy of application in harvested commodities to take advantage of its beneficial responses. Four decades have already passed since postharvest UV radiation applications began to be studied. During this time, UV treatments have been successfully evaluated for different purposes, including the selection of raw materials, the control of postharvest diseases and human pathogens, the elicitation of nutraceutical compounds, the modulation of ripening and senescence, and the induction of cross-stress tolerance. Besides the microbicide use of UV radiation, the effect that has received most attention is the elicitation of bioactive compounds as a defense mechanism. UV treatments have been shown to induce the accumulation of phytochemicals, including ascorbic acid, carotenoids, glucosinolates, and, more frequently, phenolic compounds. The nature and extent of this elicitation have been reported to depend on several factors, including the product type, maturity, cultivar, UV spectral region, dose, intensity, and radiation exposure pattern. Even though in recent years we have greatly increased our understanding of UV technology, some major issues still need to be addressed. These include defining the operational conditions to maximize UV radiation efficacy, reducing treatment times, and ensuring even radiation exposure, especially under realistic processing conditions. This will make UV treatments move beyond their status as an emerging technology and boost their adoption by industry.

Does the roof type of a house influence the presence of adult Anopheles stephensi, urban malaria vector? - evidence from a few slum settings in Chennai, India

In an urban setting, it is a difficult task to collect adult Anopheles stephensi, unlike the immature stages, due to various reasons. A longitudinal study was undertaken from January 2016 to April 2017, with CDC light traps to collect adult Anopheles stephensi and other mosquito species in houses located in a few slums of Chennai, India. A total of 203 trap collections were made indoors from human dwellings having different roof types, as well as outdoors. Three to four trap collections were made at night (18:00 to 06:00 h) once a week. Overall, Culex quinquefasciatus (64%) was the predominant mosquito species captured, followed by An. stephensi (24%). In 98 of the 203 trap collections (48.3%), at least one female An. stephensi was trapped. In all, 224 female An. stephensi were trapped, of which the majority were collected during monsoon and winter seasons. Compared to outdoors, 10% more An. stephensi, the majority of them unfed, were collected indoors, with relatively more contribution coming from asbestos-roofed houses (71.4%), followed by thatched-roof houses (47.3%). Overall, 2.2% positivity for Plasmodium vivax was detected in An. stephensi through Circumsporozoite-ELISA. Binary logistic regression model indicated that season (winter and monsoon), asbestos-roofed dwelling, lesser number of rooms in a house, and more members in a family were significant predictor variables for the odds of trapping an An. stephensi. The study brought out significant factors associated with the presence of An. stephensi in urban slums setting in Chennai, where malaria is declining. The findings would help in devising targeted, effective vector control interventions for malaria elimination in urban settings.

A comparison of BG Sentinel and CDC trap attractants for mosquito surveillance in urban and suburban areas of Montgomery and Prince George's Counties, Maryland, U.S.A

Monitoring mosquito populations is crucial for vector-borne disease surveillance. Routine mosquito surveillance in many regions of the United States is performed either by vector abatement districts or public health departments. These surveillance programs often use multiple trap types and attractants to target key mosquito species, however setting different traps with varying attractants can be expensive and labor intensive. Because funding for mosquito control is highly variable throughout the U.S., some programs may be limited in their surveillance capabilities. To determine whether a single trap-attractant combination could provide specificity for key vector and nuisance species, as well as sensitivity for rare species, we compared the BG-Sentinel 2 and CDC miniature light traps paired with CO₂, UV-LED, BG Lure, BG Sweetscent, octenol, or chicken feathers. Trapping was conducted biweekly from June/July-October 2019 and 2020 in Montgomery and Prince George's County, MD. BG traps collected significantly more Aedes albopictus than CDC traps when paired with BG Lure, Sweetscent, or octenol. BG/CO₂ traps collected both the greatest number of total mosquitoes and Culex pipiens. BG/CO₂, CDC/CO₂, and CDC/UV traps provided the most diverse collections. Trapping with the CO₂-baited BG-Sentinel is recommended as an effective strategy for general mosquito surveillance when resources are limited.

Comparing Light-Emitting-Diodes Light Traps for Catching Anopheles Mosquitoes in a Forest Setting, Western Thailand

Simple Summary

A field study was conducted in a forest to compare the effectiveness of light traps fitted with different bulbs across the wavelength spectrum. Ultraviolet (UV) fluorescent light was found to be most effective to collect adult Anopheles mosquitoes from 21:00 h to the pre-dawn hours in the dry season. These findings have important implications for monitoring vector density in the endemic malaria areas where other methods cannot be executed. A more comprehensive and systematic study of how mosquitoes respond to light would benefit Thailand’s national control program. Their potential for more precisely sampling vectors holds promise as a tool for mosquito monitoring endemic malaria areas and outbreak hotspots.

Abstract

Light traps are a common method for attracting and collecting arthropods, including disease vectors such as mosquitoes. Various types of traps have been used to monitor mosquitoes in a forest in Western Thailand. In this study, four Light Emitting Diodes (LED) light sources (UV, blue, green, and red) and two fluorescent lights (white and UV) were used to trap nocturnal adult mosquitoes. These traps were used with light alone and not any additional attractant. The experiment was conducted from 18:00 to 06:00 h. on six consecutive nights, every two months, across dry, wet, and cold seasons. All specimens were first identified by morphological features and subsequently confirmed by using PCR. We collected a total of 873 specimens of 31 species in four genera, Anopheles, Aedes, Culex, and Armigeres. Anopheles harrisoni was the predominant species, followed by Aedes albopictus, Culex brevipalpis, Culex nitropunctatus, and Armigeres (Leicesteria) longipalpis. UV fluorescent light was the most effective light source for capturing forest mosquitoes, followed by UV LED, blue LED, green LED, white fluorescent, and red LED. The optimal times for collection were from 21:00 to 03:00 h in the dry season. Our results demonstrate that appropriate sampling times and light sources should be selected for optimal efficiency in vector surveillance programs.

Evaluation of light emitting diode suction traps for the collection of livestock-associated Culicoides species in South Africa

Risk analysis of pathogens transmitted by Culicoides (Diptera; Ceratopogonidae) depends on the ability to detect all potential vectors attacking livestock in an area. Onderstepoort 220-V ultraviolet (UV) down-draught light traps are considered the gold standard for this purpose. To improve the flexibility of this trap in the field, in the absence of 220-V power, the possibility of using low-energy light emitting diodes (LEDs) was assessed. The efficiency of a standard 220-V Onderstepoort trap (30 cm 8 W fluorescent UV light tube) was compared to that of 220-V Onderstepoort traps fitted with either two, four or eight individual white LEDs. The Onderstepoort 220-V trap was also compared to a 12-V Onderstepoort trap fitted with an 8 W fluorescent UV light tube, a 12-V Onderstepoort trap with 12 individual white LEDs and 12-V and 220-V Onderstepoort traps fitted with 12 individual UV LEDs. Higher numbers of Culicoides as well as species diversity were collected with a brighter light source. The use of UV LEDs in both the 12-V and 220-V combinations was comparable to the Onderstepoort 220-V light trap with ration to species diversity collected. The Onderstepoort 220-V light trap is recommended if large numbers of Culicoides need to be collected.

Transmitted Light as Attractant with Mechanical Traps for Collecting Nocturnal Mosquitoes in Urban Bangkok, Thailand

Mosquito surveillance is the cornerstone for determining abundance, species diversity, pathogen infection rates, and temporal and spatial distribution of different life stages in an area. Various methods are available for assessing adult mosquito populations, including mechanical trap devices using different forms of attractant cues (chemical and visual) to lure mosquitoes to the trap. So-called "light traps" use various electromagnetic wavelengths to produce a variety of visible spectral colors to attract adult mosquitoes. However, this type of trapping technology has not been widely used in Thailand. This study compared the efficacy of 4 light-emitting diodes (LEDs) (blue, green, yellow, and red) and 2 fluorescent (ultraviolet [UV] and white) lights for collecting mosquitoes in urban Bangkok. Using a Latin square experimental design, 6 light traps equipped with different lights were rotated between 6 trap site locations within the Kasetsart University (KU) campus. Each location received 6 replicate collections (6 consecutive trap-nights represented 1 replicate) over 36 collection nights for a total of 216 trap-nights. Traps were operated simultaneously (1800 to 0600 h), with captured mosquitoes removed at 3-h intervals. In total, 2,387 mosquitoes consisting of 11 species across 5 genera (Aedes, Anopheles, Armigeres, Culex, and Mansonia) were captured. Collectively, Culex species represented the predominant group sampled (2,252; 94.4%). The UV light source captured 1,544 (64.7%) of the total mosquitoes collected, followed by white 389 (16.3%), with the 4 LED sources collecting between 6.8% (blue) and 1.9% (yellow). Traps equipped with UV light were clearly the most effective for capturing nocturnally active mosquito species on the KU campus.

Culicoides biting midges and mosquito fauna at three dog and cat shelters in rural and periurban areas in Northern Spain

The diversity and abundance of Culicoides (Diptera: Ceratopogonidae) and mosquitoes (Diptera: Culicidae) were studied in three animal protection centres (APCs) in Northern Spain between 1 July and 31 October 2018. Four miniature suction CDC light traps (two UV and two standard incandescent bulb traps, both types baited and non-baited with CO₂ ) were placed in each APC to compare their efficiency in the collection of these Diptera groups. A total of 1176 biting midges (14 species), 224 mosquitoes (8 species) and 1 black fly were collected and identified by both morphological and molecular approaches. The Culicoides obsoletus complex (C. obsoletus/C. scoticus) accounted for 58.2% of the total collection within the Ceratopogonidae family, whereas Culex pipiens/Cx. torrentium comprised 76.8% of the Culicidae. The input of CO₂ in light traps proved largely ineffective in improving the collections of both Diptera groups. UV-light traps were 7.8 and 2.2 times more effective than incandescent light traps in trapping Culicoides and mosquitoes, respectively. Seasonal dynamics differed between both Diptera taxa but captures of both taxa were significantly larger at the beginning of the summer. The epidemiological relevance of the most prevalent species is also discussed.

Biting Midges in Jamari National Forest, in the Brazilian Amazon, With 12 New Records of Culicoides Species (Diptera: Ceratopogonidae) for the State of Rondônia

Culicoides biting midges are small hematophagous flies, some species of which transmit pathogens to livestock and humans. In the Brazilian Amazon Basin, Culicoides diversity has remained largely unexamined. Jamari National Forest (JNF) is a conservation area in Rondônia State where research and environmental education are conducted in conjunction with the protection of natural resources, and the recovery of degraded areas. The present study augments our knowledge of Culicoides diversity in JNF. The survey collected 640 individuals from 41 species; 632 individuals were collected by HP light trap and 8 were collected by the BG Sentinel trap. Twelve species are first-time records for Rondônia: Culicoides acotylus Lutz, Culicoides albuquerquei Wirth & Blanton, Culicoides baniwa Felippe-Bauer, Culicoides bricenoi Ortiz, Culicoides brownei Spinelli, Culicoides carsiomelas Wirth & Blanton, Culicoides debilipalpis Lutz, Culicoides forattinii Ortiz, Culicoides ginesi Ortiz, Culicoides profundus Santarém, Felippe-Bauer & Trindade, Culicoides pseudoreticulatus Santarém, Felippe-Bauer & Castellón, and Culicoides spurius Santarém, Felippe-Bauer & Trindade. The most abundant species were Culicoides glabrior Macfie, Culicoides pseudodiabolicus Fox, Culicoides debilipalpis, Culicoides quasiparaensis Clastrier, and Culicoides brownei Spinelli. The present study updates the Culicoides species count in Rondônia to 55, and highlights the importance of JNF as a hotbed for biting midge diversity.

Artificial light and biting flies: the parallel development of attractive light traps and unattractive domestic lights

Light trapping is an important tool for monitoring insect populations. This is especially true for biting Diptera, where light traps play a crucial role in disease surveillance by tracking the presence and abundance of vector species. Physiological and behavioural data have been instrumental in identifying factors that influence dipteran phototaxis and have spurred the development of more effective light traps. However, the development of less attractive domestic lights has received comparatively little interest but could be important for reducing interactions between humans and vector insects, with consequences for reducing disease transmission. Here, we discuss how dipteran eyes respond to light and the factors influencing positive phototaxis, and conclude by identifying key areas for further research. In addition, we include a synthesis of attractive and unattractive wavelengths for a number of vector species. A more comprehensive understanding of how Diptera perceive and respond to light would allow for more efficient vector sampling as well as potentially limiting the risk posed by domestic lighting.

Preferential attraction of different colours of light emitting diodes for Culicoides species in West Bengal, India

The preferential attraction of adult Culicoides (Diptera: Ceratopogonidae) to specific wavelengths was studied in West Bengal, India. A total of 280 collections were made with suction light traps fitted with various colours of light emitting diodes (LEDs) placed at cattle sheds during June, August and November in 2017. In addition, the numbers that have been collected in the evening and morning were compared. Locally manufactured suction light traps fitted with ultra violet (UV), blue, green, yellow, pink, red and white LEDs were compared. UV light attracted the highest number of midges followed by blue and then green LED. Culicoides peregrinus Kieffer and Culicoides oxystoma Kieffer were the most abundant followed by Culicoides fulvus Sen and Das Gupta, Culicoides innoxius Sen and Das Gupta, Culicoides anophelis Edwards and Culicoides huffi Causey. The species composition remained similar across the wavelengths. Although significant variations in midge population have been observed across the months, no significant difference in dusk and dawn abundance was noticed. The females showed a mixed population with less parous individuals.

Sampling Considerations for Adult and Immature Culicoides (Diptera: Ceratopogonidae)

Developing sampling programs for Culicoides can be challenging due to variation in ecology and behavior of the numerous species as well as their broad distributions and habitats. In this paper, we emphasize the need to clearly define research goals to select appropriate sampling methods. This includes not just the choice of sampling device, but also choice of attractant, site, number of traps per site, the duration and frequency of sampling, and the number of traps per unit area. Animal-baited trapping using enclosure traps and direct animal aspiration is more labor-intensive but yields information on species attracted to specific hosts as well as their biting rates. Sampling immatures is discussed with respect to choosing collection sites in semiaquatic mud, soil, and rich organic habitats. Sorting and extracting larvae using emergence traps, flotation, and Berlese funnels is also discussed.

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.

Diagnosing bluetongue virus in domestic ruminants: current perspectives

This review provides an overview of current and potential new diagnostic techniques against bluetongue virus (BTV), an Orbivirus transmitted by arthropods that affects ruminants. Bluetongue is a disease currently notifiable to the World Organization for Animal Health (OIE), causing great economic losses due to decreased trade associated with bluetongue outbreaks and high mortality and morbidity. BTV cross-reacts with many antigenically related viruses including viruses that causes African Horse sickness and epizootic haemorrhagic disease of deer. Therefore, reliable diagnostic approaches to detect BTV among these other antigenically related viruses are used or being developed. The antigenic determinant for differentiation of virus species/serogroups among orbiviruses is the VP7 protein, meanwhile VP2 is serotype specific. Serologically, assays are established in many laboratories, based mainly on competitive ELISA or serum neutralization assay (virus neutralization assay [VNT]) although new techniques are being developed. Virus isolation from blood or semen is, additionally, another means of BTV diagnosis. Nevertheless, most of these techniques for viral isolation are time-consuming and expensive. Currently, reverse-transcription polymerase chain reaction (RT-PCR) panels or real-time RT-PCR are widely used methods although next-generation sequencing remains of interest for future virus diagnosis.

The efficiency of light-emitting diode suction traps for the collection of South African livestock-associated Culicoides species

Culicoides biting midges (Diptera: Ceratopogonidae) are vectors of a range of orbiviruses that cause important veterinary diseases such as bluetongue and African horse sickness. The effective monitoring of Culicoides species diversity and abundance, both at livestock and near potential wildlife hosts, is essential for risk management. The Onderstepoort 220-V ultraviolet (UV) light trap is extensively used for this purpose. Reducing its power requirements by fitting low-energy light-emitting diodes (LEDs) can lead to greater flexibility in monitoring. A comparison of the efficiency of the 220-V Onderstepoort trap (8-W fluorescent UV light) with the efficiency of the 220-V or 12-V Onderstepoort traps fitted with red, white, blue or green LEDs or a 12-V fluorescent Onderstepoort trap demonstrated the 220-V Onderstepoort trap to be the most efficient. All the results showed nulliparous Culicoides imicola Kieffer females to be the dominant grouping. Despite the lower numbers collected, 12-V traps can be used in field situations to determine the most abundant species.

Culicoides paolae and C. circumscriptus as potential vectors of avian haemosporidians in an arid ecosystem

BACKGROUND

Haemosporidians are the most important vector-borne parasites due to their cosmopolitan distribution and their wide range of hosts, including humans. Identification of their vectors is critical to highlight ecologically and epidemiologically relevant features such as host specificity or transmission routes. Biting midges of the genus Culicoides are considered the main vectors of Haemoproteus spp., yet important information on aspects such as vector feeding preferences or vector-host specificity involving haemosporidian parasites is frequently missing.

METHODS

We assessed the abundance of Culicoides circumscriptus and C. paolae and blood sources of the latter at the nests of cavity-nesting bird species (mainly the European roller Coracias garrulus) and in their surroundings. We also explored the prevalence and genetic diversity of avian haemosporidians in parous females of both species.

RESULTS

Both C. circumscriptus and C. paolae were abundant in the study area and common at European roller nests. Culicoides paolae had a diverse ornithophilic diet, feeding on at least seven bird species. Human DNA was also detected in the blood meal of some individuals. Four Haemoproteus lineages, including a new one reported here for the first time, were isolated from parous females of both biting midges.

CONCLUSIONS

Culicoides circumscriptus and C. paolae can play a locally important role in the transmission dynamics of Haemoproteus parasites in a community of cavity-nesting bird species in an arid ecosystem.

Oropouche Fever: A Review

Oropouche fever is an emerging zoonotic disease caused by Oropouche virus (OROV), an arthropod transmitted Orthobunyavirus circulating in South and Central America. During the last 60 years, more than 30 epidemics and over half a million clinical cases attributed to OROV infection have been reported in Brazil, Peru, Panama, Trinidad and Tobago. OROV fever is considered the second most frequent arboviral febrile disease in Brazil after dengue fever. OROV is transmitted through both urban and sylvatic transmission cycles, with the primary vector in the urban cycle being the anthropophilic biting midge Culicoides paraensis. Currently, there is no evidence of direct human-to-human OROV transmission. OROV fever is usually either undiagnosed due to its mild, self-limited manifestations or misdiagnosed because its clinical characteristics are similar to dengue, chikungunya, Zika and yellow fever, including malaria as well. At present, there is no specific antiviral treatment, and in the absence of a vaccine for effective prophylaxis of human populations in endemic areas, the disease prevention relies solely on vector control strategies and personal protection measures. OROV fever is considered to have the potential to spread across the American continent and under favorable climatic conditions may expand its geographic distribution to other continents. In view of OROV's emergence, increased interest for formerly neglected tropical diseases and within the One Health concept, the existing knowledge and gaps of knowledge on OROV fever are reviewed.

The Dark Side of Light Traps

Light-baited suction traps are one of the most widely used tools for vector surveillance. Their popularity stems from ease of use even in remote locations, range and abundance of species caught, and low cost. The availability of smaller, portable models, like the CDC miniature light trap, have further increased their ubiquity in entomological field studies. However, when researchers have looked, light trap collections are usually biased in ways that may affect data interpretation for epidemiological studies. If used alone, light traps may fail to collect important or infected vectors, and light traps are inefficient or ineffective when competing ambient light is present. In this article, we discuss these biases and limitations in terms of their effect on collection efficiency, population data, and pathogen detection. While light trap data certainly have a purpose, an over-reliance on light trapping risks drawing false conclusions about vector populations and vector-borne disease epidemiology. These concerns are especially troubling when light trap data are used to inform policy decisions meant to protect human and animal health. Particularly when a species' response to light is unknown or poorly characterized, light traps should be used in conjunction with supplemental sampling methods. Researchers conducting vector surveillance field studies should carefully consider their study design and objectives when deciding on a trapping method or methods, and specifically endeavor to understand the limitations of their data. Only then can researchers take advantage of the best attributes of light traps while avoiding their dark side.