Response of phlebotomine sand flies to light-emitting diode-modified light traps in southern Egypt

Field comparison of broad-spectrum white LED-baited traps with narrow-spectrum green LED-baited traps in the capture of Anopheles mosquitoes (Diptera: Culicidae)

Light-Emitting Diodes (LEDs) have been effective light sources in attracting Anopheles mosquitoes, but the broad-spectrum white light, even with a wide-ranging application in lighting, have not been evaluated yet. In this study, the white light was field evaluated against the green one in the light trapping of anopheline mosquitoes by using two non-suction Silva traps and two CDC-type suction light traps. Anopheline mosquitoes were captured for two 21-night periods of collecting (2022 and 2023). In the first period, two LEDs were used per Silva trap, but three were used in the second one to increase the luminance/illuminance at traps. A CDC-type suction light trap equipped with an incandescent lamp was used in 2022 and a CDC-type suction light trap equipped with a 6 V-white light (higher luminance/illuminance) in 2023. A total of eight species and 3,289 specimens were captured in both periods. The most frequent species were Anopheles triannulatus s.l., An. goeldii, An. evansae and An. argyritarsis. In 2022, white LEDs were less attractive to anopheline mosquitoes than the other light sources, but without statistical difference among treatments (F = 2.703; P = 0.0752; df = 2). In 2023, even with an increased luminance/illuminance at traps, no statistical difference was found between the two LED-baited Silva traps (F = 6.690; P = 0.0024; df = 2), but rather between the 6 V-white-baited CDC-type suction light trap and green-baited Silva traps. Due to some drawbacks and the lower abundance of individuals caught by using white LEDs, the narrow-banded green LEDs is preferable to white ones for attracting anophelines.

Complementary use of visual and olfactory cues to assess capture of Bactrocera dorsalis (Hendel): Implementation and field verification via an IoT-based automatic monitoring system

This study examined the effect of combining visual and olfactory cues to attract oriental fruit flies (OFFs). Six different colored light-emitting diodes (LEDs) served as a visual attractant and methyl eugenol served as olfactory bait to lure male flies. An internet of things (IoT)-based pest monitoring system, consisting of sensor nodes, a gateway, and automatic counting traps, was deployed in the field to automatically collect environmental data and pest counts. The results of the calibrated experiments indicated that green, yellow, or red LEDs exhibited better performance in attracting flies than white, purple, or blue LEDs or no LEDs. With an accurate combination of visual and olfactory cues, the proposed IoT-based pest monitoring system may be an effective tool in agricultural pest management, given its advantages for efficiently capturing OFFs in a labor and time saving manner, providing accurate information regarding increases in pest populations, and enabling long-term, real-time data collection.

Field evaluation of a new suction light trap for the capture of phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae), vectors of leishmaniasis

Phlebotomine sand flies are crepuscular and nocturnal small dipteran insects in the family Psychodidae. Several disease agents, including Leishmania parasites, are transmitted to humans and other vertebrate hosts by the bite of an infected female sand fly. As part of leishmaniasis surveillance programs, light traps have been routinely used in sand fly collections. In this context, new trapping devices are always being required to improve vector monitoring. Here, the efficiency of a new suction light trap, named Silva suction trap or SS trap, was field evaluated in collecting sand flies. Two SS traps, one with green (520 nm, 15,000 mcd) and the other with white (wide spectrum, 18,000 mcd) LEDs, and one CDC-type trap were deployed in a rural forested environment. A total of 4686 phlebotomine sand flies were captured. The most frequent species were females of the Ps. Chagasi series (77.8%) followed by males of Ps. wellcomei (11.6%), Nyssomyia whitmani (3.3%), and Bichromomyia flaviscutellata (2.4%). The CDC-type light trap collected 101.9 ± 20.89 sand flies and 14 species, followed by the white-baited SS trap (87.78 ± 16.36, 14), and the green-baited SS trap (70.61 ± 14.75, 15), but there were no statistically significant differences among traps. A discussion on the considerable advantages of the use of SS traps over CDC traps is included. In this study, the Silva suction trap proved to be efficient and can be an alternative to CDC traps for monitoring adult phlebotomine sand fly populations.

Light-emitting diodes as visual attractants to phlebotomine sand flies (Diptera: Psychodidae): A mini-review

Phlebotomine sand flies are responsible for the transmission of different pathogens, including flagellate protozoan of the genus Leishmania. To locate a vertebrate host, females use chemical cues called kairomones, which are also used by males and females to locate carbohydrate sources of food. In addition to these chemical cues, visual cues (such as light and color) can play a key role in determining host location. In this way, incandescent white light is widely used to capture these insects in the field, being more recently replaced by light-emitting diode (LEDs) technology, which can be used with different colors. In this review, we summarize the main results of the use of LEDs as attractants for sand flies. Considering the different LEDs colors, blue and green are responsible for catching the highest number of sand fly species, especially for field trials conducted in New World countries. The intensity of light colors is an important factor to be considered, but so far little explored. In general, the use of LEDs can be considered as a feasible tool for the improvement of light traps. Future research is required to assert the contribution of different colors individually, in different combinations and intensities, as well as the possible synergistic effect of LEDs in association with attractive compounds in the behavior of sand flies.

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.

The spectral composition of a white light influences its attractiveness to Culex pipiens mosquitoes

Insect attraction to artificial light can potentially facilitate disease transmission by increasing contact between humans and vectors. Previous research has identified specific wavelength bands, such as yellow and red, that are unattractive to biting flies. However, narrow-band, non-white lights are unsuitable for home lighting use as their very poor color rendering is often considered aesthetically undesirable. The creation of a white light that is unattractive to insects has so far remained elusive. White light can be created by combining a number of narrow-band light-emitting diodes (LEDs). Through choice chamber experiments on Culex pipiens (Cx. pipiens) mosquitoes, we examine whether combining specific wavelength bands has an additive, subtractive or synergistic effect on insect attraction. We show that a white light created by combining narrow-band red, green and blue (RGB) LEDs is less attractive to Cx. pipiens than a broad-spectrum white light; and that a white light created by combining narrow-band blue and yellow LEDs is more attractive than a broad-spectrum white light. White light produced by RGB combinations could therefore serve as a safer and cheaper light in countries where phototactic vectors and vector-borne disease are endemic.

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.

Electrophysiological detection of visible wavelengths of artificial lights inducing take-off in adults of Rhodnius prolixus (Hemiptera: Triatominae)

Rhodnius prolixus is the most important vector of Trypanosoma cruzi in the northern part of South America. The compound eyes in adults of R. prolixus are involved in the nocturnal flight dispersion from sylvatic environments into human dwellings. During this behavior, the artificial lights play an important role in attracting R. prolixus; however, it is still not clear whether the compound eyes of this species use different visible wavelengths as a cue during active dispersion. We applied electrophysiological (electroretinography or ERG) and behavioral (take-off) experiments in a controlled laboratory setting to determine the spectral sensitivity of the compound eyes and the attraction of R. prolixus adults to discrete visible wavelengths. For the ERG experiments, flashes of 300 ms at wavelengths ranging between 350 and 700 nm at a constant intensity of 3.4 µW/cm2 were tested after adaptation to darkness and to blue and yellow lights. For the behavioral experiments, the adults were exposed to nine visible wavelengths at three different intensities, and their direction of take-off in an experimental arena was established with circular statistics. The ERG results showed peaks of spectral sensitivity at 470-490 nm and 520-550 nm in adults, while behavioral experiments showed attractions to blue, green and red lights, depending on the intensity of the light stimuli. The electrophysiological and behavioral results confirm that R. prolixus adults can detect certain wavelengths in the visible spectrum of light and be attracted to them during take-off.

Use of light emitting diodes (LEDs) are effective and useful for sand fly ecoepidemiology studies in an Amazonian environment

One strategy to identify transmission foci is based on vector monitoring, and efficient methods are important for vector control. Our study evaluated different light sources (red, green, ultraviolet, blue, and incandescent light) to capture sand fly in Porto Velho, Brazil. We also evaluated Leishmania and blood meal sources in females. A total of 1,943 individuals were identified in 45 species level-taxa, with Trichophoromyia ubiquitalis (Mangabeira) (n=364), Nyssomyia antunesi (n=241), Bichromomyia flaviscutellata (Mangabeira) (n=222), and Psychodopygus davisi (Root) (n=148) being the most abundant. Incandescent light captured most individuals (n=589), followed by blue (n=471), green (n=452), ultraviolet (n=281) and red (n=150). No significant difference was observed between the species composition and lights (PERMANOVA: Pseudo F = 1.29, p = 0.14, NMDS: Stress 0.18). The Shannon and Simpson indices demonstrated a high diversity captured using all lights. Our data demonstrated that LEDs are alternative devices for sand fly capture, with blue and green LEDs presenting similar results to incandescent light. 53 pools were analyzed, only one pool was positive for kDNA and hsp70 targets [Nyssomyia fraihai (Martins, Falão & Silva)] and identified as Endotrypanum spp., suggesting that other trypanosomatids may circulate in the locality. Choloepus hoffmanni (two-toed sloth) Peters, Homo sapiens Linnaeus, Proechimys gardneri (Gardner's spiny rat) Da Silva, and Tamandua tetradactyla (lesser anteater) (Linnaeus) were blood meal sources identified in females, increasing the knowledge about sources used by these insects.

Semi-field evaluation of novel chemical lures for Aedes aegypti, Culex quinquefasciatus, and Anopheles minimus (Diptera: Culicidae) in Thailand

BACKGROUND

Entomological surveillance is an important means of assessing the efficacy of insect vector management programs and estimating disease transmission thresholds. Among baited traps, Biogents' BG-Sentinel (BGS) trap baited with BG-Lure is considered to have the most similar outcome to, and be a possible replacement for, human-landing catches for the epidemiologically relevant monitoring of adult Aedes aegypti and Culex quinquefasciatus. In contrast to the BGS trap, the Black Hole ultraviolet (UV) light trap, which is widely used to catch nocturnal flying insects, is not baited with synthetic human odor-mimicking lures.

METHODS

We evaluated the L-lactic acid-based Kasetsart University (KU)-lures nos. 1-6 as novel candidate chemical lures for the diurnal species Ae. aegypti and the nocturnal species Cx. quinquefasciatus using two commercial traps (the BGS trap and the Black Hole UV light trap) in a semi-field screen (SFS) house. Firstly, we optimized the dose of each KU-lure in an SFS house (140 m3). Secondly, six different candidate KU-lures were screened by comparing their percent attraction using a single discriminating dose (0.5 g). Finally, we evaluated the synergism of the KU-lures selected in this way with commercially available traps.

RESULTS

BGS traps baited with KU-lure no. 1 exhibited the greatest percent attraction for Ae. aegypti (29.5% ± 14.3%), whereas those baited with KU-lure no. 6 most strongly attracted Cx. quinquefasciatus (33.3% ± 10.7%). Interestingly, BGS traps treated with 10 g BG-Lure did not significantly attract more Ae. aegypti or Cx. quinquefasciatus than the untreated BGS traps. CO2 at a flow rate of 250 ml/min most strongly attracted both Ae. aegypti and Cx. quinquefasciatus (42.2% ± 14.2% and 75.1% ± 16.9%, respectively). BGS and Black Hole UV light traps with KU-lure no. 6 exhibited a stronger attraction for Cx. quinquefasciatus than untreated traps, and the percent attraction did not differ between the treated traps.

CONCLUSIONS

Synergistic effects of KU-lures nos. 1 and 6 with the mosquito traps were demonstrated for both the diurnal and nocturnal species in the SFS house assays. However, further studies are urgently needed for the development of species-specific lures to increase trap efficacy in the field for local vector mosquitoes in Thailand.

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.

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.

Field evaluation of four commercial light traps, trap placement, and effect of carbon dioxide on phlebotomine sand fly collection in northern Thailand

Several light trap devices have been invented and developed to assess the abundance of sand flies. Traps available in the market have different designs and attractant combinations to catch sand fly vectors. We evaluated the efficacy of four commercial light traps and determined the effect of trap placement and carbon dioxide (CO₂) on sand fly collection in northern Thailand. Trap evaluations were conducted at two natural caves located in Chiang Rai province, Thailand. In the first part of the study, the efficacies of four trap types including the Centers for Disease Control miniature light trap (CDC LT), Encephalitis Vector Survey trap (EVS), CDC Updraft Blacklight trap (CDC UB), and Laika trap (LK) were evaluated and compared using a Latin square experimental design. The second half of the study evaluated the influence of trap placement and CO₂ on sand fly collection. Additionally, CDC LT were placed inside, outside, and at the entrance of caves to compare the number of sand flies collected. For the trap efficacy experiment, a total of 11,876 phlebotomine sand flies were collected over 32 trap-nights. Results demonstrated that CDC LT, CDC UB, and LK collected significantly more sand flies than EVS (P > 0.05). However, there were no significant differences between the numbers of sand flies collected by CDC LT, CDC UB, and LK. A total of 6,698 sand flies were collected from the trap placement and CO₂ experiment over 72 trap-nights. Results showed that CO₂ did not influence the numbers of sand flies captured (P < 0.05), whereas trap placement at the entrance of the caves resulted in collection of significantly more sand flies than traps placed inside and outside of the caves. We found the CDC LT, CDC UB, and LK without CO₂ captured the greatest amount of sand flies. This was particularly observed when traps were placed at the entrance of a cave, perhaps because of the greater passage of stimuli caused by wind flow at the entrance of the cave. The light traps in this study can be used effectively to collect sand fly vectors in northern Thailand.

Comparison of sand fly trapping approaches for vector surveillance of Leishmania and Bartonella species in ecologically distinct, endemic regions of Peru

BACKGROUND

In Peru, the information regarding sand fly vectors of leishmaniasis and bartonellosis in the Amazon region is limited. In this study, we carried out sand fly collections in Peruvian lowland and highland jungle areas using different trap type configurations and screened them for Leishmania and Bartonella DNA.

METHODOLOGY/PRINCIPAL FINDINGS

Phlebotomine sand flies were collected in Peruvian Amazon jungle and inter Andean regions using CDC light trap, UV and color LED traps, Mosquito Magnet trap, BG Sentinel trap, and a Shannon trap placed outside the houses. Leishmania spp. screening was performed by kDNA PCR and confirmed by a nested cytochrome B gene (cytB) PCR. Bartonella spp. screening was performed by ITS PCR and confirmed by citrate synthase gene (gltA). The PCR amplicons were sequenced to identify Leishmania and Bartonella species. UV and Blue LED traps collected the highest average number of sand flies per hour in low jungle; UV, Mosquito Magnet and Shannon traps in high jungle; and Mosquito Magnet in inter Andean region. Leishmania guyanensis in Lutzomyia carrerai carrerai and L. naiffi in Lu. hirsuta hirsuta were identified based on cytB sequencing. Bartonella spp. related to Bartonella bacilliformis in Lu. whitmani, Lu. nevesi, Lu. hirsuta hirsuta and Lu. sherlocki, and a Bartonella sp. related to Candidatus B. rondoniensis in Lu. nevesi and Lu. maranonensis were identified based on gltA gene sequencing.

CONCLUSIONS/SIGNIFICANCE

UV, Blue LED, Mosquito Magnet and Shannon traps were more efficient than the BG-Sentinel, Green, and Red LED traps. This is the first report of L. naiffi and of two genotypes of Bartonella spp. related to B. bacilliformis and Candidatus B. rondoniensis infecting sand fly species from the Amazon region in Peru.

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.

Phlebotomines (Diptera: Psychodidae) and Mosquitoes (Diptera: Culicidae) Surrounding an Environmental Protection Zone in the Metropolitan Region of Natal: Use of Light-Emitting Diode (LED) Bulbs in Entomological Surveillance

Entomological surveillance is very important for parasite and arbovirus vector control programs. Light traps with incandescent bulbs are used to attract insects and analyze the factors that contribute to the occurrence of species surrounding an environmental protection zone. Phlebotomine and mosquito abundance and their diversity were analyzed. Captures occurred monthly using six CDC light traps with two incandescent bulbs, two blue and two red LED lights. A total of 2211 phlebotomines of seven species and 4486 mosquitoes belonging to 20 taxa were captured. Different phlebotomine and mosquito species were found in the forest and peridomestic environments, with a predominance of the sand fly Evandromyia walkeri (Newstead) and the mosquito Coquillettidia venezuelensis (Theobald). There was a significant difference in the abundance of sand flies captured with the three bulbs tested, the blue bulb being the most efficient. The Shannon-Wiener diversity index showed that the trap equipped with a red LED light obtained a higher value than that of the blue LED and incandescent bulb. Analyses showed that the potential vectors and non-vectors of the two groups circulate between the forest and the peridomestic environment, suggesting an adaptation process of species to the altered environment. An incandescent light bulb can be substituted by an LED bulb, without compromising the sensitivity of the method. A blue LED is indicated for the abundant capture of mosquitoes and sand flies, while a red LED obtains a better result in terms of species diversity per capture.

Understanding sand fly sampling methods: sticky traps are attraction-based and not interceptive sampling tools of Phlebotomus orientalis

BACKGROUND

Sticky traps are generally viewed as interceptive sand fly sampling methods; although no previous experimental evidence has supported this assumption. In this study, we tested this assumption experimentally for Phlebotomus orientalis, the principal vector of visceral leishmaniasis in East Africa, and propose an explanation for the highly male-biased collection of sticky traps.

METHODS

A number of field experiments were carried out in March-June 2016-2019, in Gedarif state, eastern Sudan. In the first experiment, we compared numbers of P. orientalis caught on sticky traps made of black, red, transparent, white, yellow, green and blue A4 size papers set simultaneously at different lunar light conditions. In the second and third experiments, we compared numbers of P. orientalis captured on sticky traps placed side-by-side horizontally or vertically on the ground, or horizontally on a 15 cm height stool. We also witnessed mating behaviour of sand flies following their landing on un-sticky papers placed on the ground.

RESULTS

Phlebotomus orientalis showed significant attraction to white, yellow and transparent traps, with negligible numbers caught on the black and the red traps. Similarly, significantly higher numbers of P. orientalis were attracted to the horizontal traps, resulting in an 8-fold increase in sand fly trapping efficacy as compared to the vertical traps. Placing the traps on the stools resulted in significant reduction in this attraction. In contrast to the sticky traps that captured only very few females; we found that when male sand flies land on un-sticky white paper they successfully lure females and copulate with them.

CONCLUSIONS

We demonstrate that, for P. orientalis, sticky traps are more attractant-based than interception-based sampling tools. Further, our findings support the notion that males of this sand fly species likely utilize the bright surface of the trap papers to perform mating rituals that attract the females for copulation. However, pre-mature death in the sticky oil hampers the completion of these rituals, and thus results in failure to attract the females. These findings inform our understanding of P. orientalis behaviour and have important implications for optimization of sticky trap design for vector surveillance purposes.

Phlebotomus papatasi sand fly predicted salivary protein diversity and immune response potential based on in silico prediction in Egypt and Jordan populations

Phlebotomus papatasi sand flies inject their hosts with a myriad of pharmacologically active salivary proteins to assist with blood feeding and to modulate host defenses. In addition, salivary proteins can influence cutaneous leishmaniasis disease outcome, highlighting the potential of the salivary components to be used as a vaccine. Variability of vaccine targets in natural populations influences antigen choice for vaccine development. Therefore, the objective of this study was to investigate the variability in the predicted protein sequences of nine of the most abundantly expressed salivary proteins from field populations, testing the hypothesis that salivary proteins appropriate to target for vaccination strategies will be possible. PpSP12, PpSP14, PpSP28, PpSP29, PpSP30, PpSP32, PpSP36, PpSP42, and PpSP44 mature cDNAs from field collected P. papatasi from three distinct ecotopes in the Middle East and North Africa were amplified, sequenced, and in silico translated to assess the predicted amino acid variability. Two of the predicted sequences, PpSP12 and PpSP14, demonstrated low genetic variability across the three geographic isolated sand fly populations, with conserved multiple predicted MHCII epitope binding sites suggestive of their potential application in vaccination approaches. The other seven predicted salivary proteins revealed greater allelic variation across the same sand fly populations, possibly precluding their use as vaccine targets.

Seasonal variation of sand fly populations in Kala-azar endemic areas of the Malda district, West Bengal, India

Vector control is one of the main aspects to reach the target of eliminating visceral leishmaniasis from Indian sub-continent as set by the World Health Organisation. Data on different aspects of vector like ecology, behaviour, population dynamics and their association with environmental factors are very important for formulating an effective vector control strategy. The present work was designed to study the species abundance and impact of environmental factors on population dynamics of vector P. argentipes in a visceral leishmaniasis endemic area of Malda district, West Bengal. Adult sand flies were collected using light traps and mouth aspirators from twelve kala-azar affected villages of Habibpur block of Malda district, on a monthly basis from January to December, 2018. Morphological and molecular methods were used for species identification. Population dynamics were assessed by man hour density and per night per trap collection. Data were analysed using SPSS software to determine the impact of environmental factors on vector population P. argentipes was found to the predominant species and prevalent throughout the year. A significantly higher number of sand flies were collected from cattle sheds than human dwellings and peri-domestic vegetation. A portion of the P. argentipes population was exophilic and exophagic as evidenced by their collection from peri-domestic vegetation. The highest population density was recorded during April to September. Population dynamics were mostly influenced by average temperature along humidity and rain fall. Resting behaviour of sand flies was not restricted to the lower portion of the wall but equally distributed throughout the wall and ceiling. Programme officials should consider management of outdoor populations of the sand flies and timings of indoor residual spray for chemical control purpose.

Exploiting the Synergistic Effect of Kairomones and Light-Emitting Diodes on the Attraction of Phlebotomine Sand Flies to Light Traps in Brazil

The synergistic effect of light-emitting diodes (LEDs) and kairomones on the attraction of sand flies to light traps was evaluated. Octenol and lactic acid were used as chemical attractants. Green LEDs and the incandescent lamps were used as light attractants. Five CDC-type light traps with the respective combination of attractants (incandescent lamp, incandescent lamp + chemical attractant, green LED, green LED + chemical attractant, and chemical attractant alone [without light]) were set between 18:00 and 06:00 following a Latin square design. A total of 6,536 sand flies and 16 species were collected. The most frequent species collected was Lutzomyia longipalpis (Lutz & Neiva, 1912) (Diptera, Psychodidae) accounting for 43.21% of all individuals. Order of success (mean, SD) of lactic acid attractant fly capture was as follows: LED + lactic acid (36.83 ± 4.74), LED alone (34.87 ± 4.61), incandescent lamp + lactic acid (22.80 ± 3.19), incandescent lamp alone (12.67 ± 2.03), and lactic acid (0.46 ± 0.13). Order of success of octenol attractant fly capture was as follows: LED + octenol (37.23 ± 5.61), LED alone (35.77 ± 5.69), incandescent lamp + octenol (18.63 ± 3.28), incandescent lamp alone (14.67 ± 2.86), and octenol alone (1.80 ± 0.65). With exception of lactic acid + incandescent light, chemical synergists played no part in significantly increasing light trap capture of phlebotomine sand flies. However, the use of LEDs, with or without such attractants, provided significantly higher capture compared to the incandescent lamp with or without such chemicals, showing that LEDs are suitable and efficient light sources for surveillance and monitoring of phlebotomine sand flies in Brazil.

Evaluation of an ultraviolet LED trap for catching Anopheles and Culex mosquitoes in south-eastern Tanzania

BACKGROUND

Improved surveillance techniques are required to accelerate efforts against major arthropod-borne diseases such as malaria, dengue, filariasis, Zika and yellow-fever. Light-emitting diodes (LEDs) are increasingly used in mosquito traps because they improve energy efficiency and battery longevity relative to incandescent bulbs. This study evaluated the efficacy of a new ultraviolet LED trap (Mosclean) against standard mosquito collection methods.

METHODS

The study was conducted in controlled semi-field settings and in field conditions in rural south-eastern Tanzania. The Mosclean trap was compared to commonly used techniques, namely CDC-light traps, human landing catches (HLCs), BG-Sentinel traps and Suna traps.

RESULTS

When simultaneously placed inside the same semi-field chamber, the Mosclean trap caught twice as many Anopheles arabiensis as the CDC-light trap, and equal numbers to HLCs. Similar results were obtained when traps were tested individually in the chambers. Under field settings, Mosclean traps caught equal numbers of An. arabiensis and twice as many Culex mosquitoes as CDC-light traps. It was also better at trapping malaria vectors compared to both Suna and BG-Sentinel traps, and was more efficient in collecting mosquitoes indoors than outdoors. The majority of An. arabiensis females caught by Mosclean traps were parous (63.6%) and inseminated (89.8%). In comparison, the females caught by CDC-light traps were 43.9% parous and 92.8% inseminated.

CONCLUSIONS

The UV LED trap (Mosclean trap) was efficacious for sampling Anopheles and Culex mosquitoes. Its efficacy was comparable to and in some instances better than traps commonly used for vector surveillance. The Mosclean trap was more productive in sampling mosquitoes indoors compared to outdoors. The trap can be used indoors near human-occupied nets, or outdoors, in which case additional CO2 improves catches. We conclude that this trap may have potential for mosquito surveillance. However, we recommend additional field tests to validate these findings in multiple settings and to assess the potential of LEDs to attract non-target organisms, especially outdoors.

Diel periodicity and visual cues guide oviposition behavior in Phlebotomus papatasi, vector of old-world cutaneous leishmaniasis

Background

Phlebotomine sand flies are vectors of human leishmaniases, important neglected tropical diseases. In this study, we investigated diel patterns of oviposition behavior, effects of visual cues on oviposition-site selection, and whether these affect the attraction of gravid Phlebotomus papatasi (Scopoli), the vector of old-world cutaneous leishmaniasis, to olfactory cues from oviposition sites.

Methodology/principal findings

To evaluate these questions, we conducted a series of experiments using attraction and oviposition assays within free-flight test chambers containing gravid females entrained under a 14:10 hrs light:dark photoperiod. By replacing sticky-screens or moist filter papers every three hours, we showed that oviposition site search occurs mainly in the latest part of the night whereas peak oviposition occurs during the early part of the night. Behavioral responses to olfactory oviposition cues are regulated by time-of-day and can be disrupted by transient exposure to a constant darkness photoperiod. Gravid females, but not any other stage, age, or sex, were attracted to dark, round oviposition jars, possibly resembling rodent burrow openings. This visual attraction disappeared in the absence of an illumination source. Egg deposition rate was not affected by jar color. Olfactory cues had the strongest effect when the visual cues were minimal.

Conclusion and significance

Our study showed, for the first time, that visual cues in the form of oviposition-site color, lighting level, and photoperiod are important in guiding the oviposition behavior of phlebotomine sand flies. Furthermore, such visual cues could modify the flies’ sensitivity to olfactory oviposition cues. Our results suggest that chemosensory and visual cues are complementary, with visual cues used to orient gravid females towards oviposition sites, possibly at long- to medium-ranges during crepuscular periods, while olfactory cues are used to approach the burrow in darkness and assess its suitability at close-range. Implications to sand fly control are discussed.

Sand flies are vectors of human leishmaniases, an important neglected tropical disease. An alternative approach to the conventional delivery of an insecticide to the vector is to bring the vector to the insecticide using oviposition (egg-laying)-site attractants. Olfactory cues originating from organic matter have been identified as important sources of oviposition attractants. However, nothing is known regarding visual assessment of oviposition sites by sand flies. Also, little is understood about diel egg-laying patterns of sand flies. Finally, it is not known if visual cues and time-of-day may affect their sensitivity to olfactory cues. In this study, we investigated these questions in a series of lab experiments using free-flight cage arenas, with Phlebotomus papatasi (vector of cutaneous leishmaniasis). We showed that peak oviposition-site search and sensitivity to olfactory cues occurs mainly in the latest part of the night whereas peak oviposition occurs during the early part of the night. We demonstrated that only gravid females, but not any other stage or sex, were attracted to dark, round oviposition jars resembling burrow openings. Finally, we showed that sensitivity to olfactory cues is reduced in the presence of strong visual cues and in the absence of natural diel photoperiod.

Centers for Disease Control-type light traps equipped with high-intensity light-emitting diodes as light sources for monitoring Anopheles mosquitoes

In this study the phototactic response of anopheline mosquitoes to different luminous intensity light-emitting diodes (LEDs) was investigated. Centers for Disease Control-type light traps were changed by replacement of the incandescent lamps by 5 mm round type green (520 nm) and blue (470 nm) LEDs of different luminous intensities: green-LED traps with luminous intensities of 10,000, 15,000 and 20,000 millicandela (mcd) and the blue-LED traps with luminous intensities of 4000, 12,000 and 15,000 mcd. Our data showed that increasing luminous intensity has an effect on the attraction of anopheline mosquitoes to light traps, highlighting the importance of taking LEDs and light sources of high luminous intensity into account when using light-trap collections in monitoring populations of Anopheles species.

Do Different LED Colours Influence Sand Fly Collection by Light Trap in the Mediterranean?

Light traps represent the most used attractive system to collect and monitor phlebotomine sand flies. Recent studies have suggested that light traps can be easily upgraded by the use of light-emitting diode (LED) with positive effects on trap design, weight, and battery life. However, scant data on the effect of different LED colours on the attractiveness to phlebotomine sand fly species are available in literature. In this study, the capture performances of light traps equipped with different LED colours on phlebotomine sand fly species indigenous in the Mediterranean area were evaluated. Phlebotomine sand fly collections were performed using a classical light trap (CLT), equipped with a traditional incandescent lamp, and five Laika 4.0 light traps supplied, each with LED of different colours and wavelengths: (i) white; (ii) red; (iii) green; (iv) blue; (v) UV. Light traps were set for three consecutive nights fortnightly from May to October 2017 and climate data recorded using a meteorological station. A total of 411 phlebotomine sand flies (191 males and 220 females), belonging to three different species, namely, Phlebotomus perniciosus (n= 298, 141 males and 157 females), Sergentomyia minuta (n=110, 48 males and 62 females), and Phlebotomus neglectus (n=3, 2 males and 1 females) were collected. Abundance of capture was influenced by colours of LED and time. The highest number of phlebotomine sand flies was captured on June (P<0.01) and by UV LED (P<0.01). As regard to species, P. perniciosus was mainly captured by UV LED on June (P<0.01). No effect of time (P>0.05) or LED colour (P>0.05) was recorded for S. minuta and P. neglectus. According to the results of the present study light trap equipped with UV LED can represent an effective tool for the capture of sand fly species in the Mediterranean area.

The effect of luminous intensity on the attraction of phlebotomine sand flies to light traps

To improve the efficiency of light traps in collecting phlebotomine sand flies, the potential effects of luminous intensity on the attraction of these insects to traps were evaluated. Sand flies were collected with Hooper Pugedo (HP) light traps fitted with 5-mm light-emitting diodes (LED) bulbs: green (520 nm wavelength-10,000, 15,000 and 20,000 millicandela (mcd) and blue (470 nm-4,000, 12,000 and 15,000 mcd). A total of 3,264 sand flies comprising 13 species were collected. The collected species were Lutzomyia longipalpis (Lutz & Neiva) (Diptera: Psychodidae) (52.48%), Evandromyia evandroi (Costa Lima & Antunes, 1939) (Diptera: Psychodidae) (32.90%) and Micropygomyia goiana (Martins, Falcão, & Silva) (Diptera: Psychodidae) (9.76%). An increase in luminous intensity of the LEDs increased the size of the sand fly catch. The lower luminous intensity of green (10,000 mcd) attracted an average of 13.7 ± 2.8 sand flies/trap per night and the other luminous intensities accounted for a mean of 24.1 ± 4.0 (15,000 mcd) and 28.2 ± 5.0 (20,000 mcd) sand flies/trap per night. Regarding the blue wavelength, the lower luminous intensity (4,000 mcd) attracted an average of 27.4 ± 4.1 sand flies/trap per night, followed by 12,000 mcd (37.6 ± 8.7) and 15,000 mcd (40.5 ± 7.3). Based on our data, the luminous intensity of light traps should be considered when developing light traps for monitoring or controlling phlebotomine sand flies.

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.

Field evaluation of a new light trap for phlebotomine sand flies

Light traps are one of the most common attractive method for the collection of nocturnal insects. Although light traps are generally referred to as "CDC light traps", different models, equipped with incandescent or UV lamps, have been developed. A new light trap, named Laika trap 3.0, equipped with LED lamps and featured with a light and handy design, has been recently proposed into the market. In this study we tested and compared the capture performances of this new trap with those of a classical light trap model under field conditions. From May to November 2013, a Laika trap and a classical light trap were placed biweekly in an area endemic for sand flies. A total of 256 sand fly specimens, belonging to 3 species (Sergentomyia minuta, Phlebotomus perniciosus, Phlebotomus neglectus) were collected during the study period. The Laika trap captured 126 phlebotomine sand flies: P. perniciosus (n=38); S. minuta (n=88), a similar number of specimens (130) and the same species were captured by classical light trap which collected also 3 specimens of P. neglectus. No significant differences in the capture efficiency at each day of trapping, neither in the number of species or in the sex of sand flies were observed. According to results of this study, the Laika trap may be a valid alternative to classical light trap models especially when handy design and low power consumption are key factors in field studies.

Practical Guidelines for Studies on Sandfly-Borne Phleboviruses: Part II: Important Points to Consider for Fieldwork and Subsequent Virological Screening

In this series of review articles entitled "Practical guidelines for studies on sandfly-borne phleboviruses," the important points to be considered at the prefieldwork stage were addressed in part I, including parameters to be taken into account to define the geographic area for sand fly trapping and how to organize field collections. Here in part II, the following points have been addressed: (1) factors influencing the efficacy of trapping and the different types of traps with their respective advantages and drawbacks, (2) how to process the trapped sand flies in the field, and (3) how to process the sand flies in the virology laboratory. These chapters provide the necessary information for adopting the most appropriate procedures depending on the requirements of the study. In addition, practical information gathered through years of experience of translational projects is included to help newcomers to fieldwork studies.

Behavioral Responses of Nymph and Adult Cimex lectularius (Hemiptera: Cimicidae) to Colored Harborages

Behavioral bioassays were conducted to determine whether bed bug adults and nymphs prefer specific colored harborages. Two-choice and seven-choice behavioral color assays indicate that red (28.5%) and black (23.4%) harborages are optimal harborage choices for bed bugs. Yellow and green harborages appear to repel bed bugs. Harborage color preferences change according to gender, nutritional status, aggregation, and life stage. Female bed bugs prefer harborages with shorter wavelengths (lilac-14.5% and violet-11.5%) compared to males, whereas males prefer harborages with longer wavelengths (red-37.5% and black-32%) compared with females. The preference for orange and violet harborages is stronger when bed bugs are fed as opposed to when they are starved. Lone bed bugs (30%) prefer to be in black harborages while red harborages appear to be the optimum harborage color for bed bugs in more natural mixed aggregations (35.5%). Bed bug nymphs preferred different colored harborages at each stage of development, which is indicative of their developing eye structures and pigments. First instars showed no significant preference for any colored harborage soon after hatching. However, by the fifth instar, 27.5% of nymphs significantly preferred red and black harborages (which was a similar preference to adult bed bugs). The proportion of oviposited eggs was significantly greater under blue, red, and black harborages compared to other colored harborages tested. The use of visual cues such as specific colors offers great potential for improving bed bug monitoring tools by increasing trap captures.

Comparative Field Evaluation of Different Traps for Collecting Adult Phlebotomine Sand Flies (Diptera: Psychodidae) in an Endemic Area of Cutaneous Leishmaniasis in Quintana Roo, Mexico

Phlebotominae are the vectors of Leishmania parasites. It is important to have available surveillance and collection methods for the sand fly vectors. The objectives of the present study were to evaluate and compare traps for the collection of sand fly species and to analyze trap catches along months and transects. Field evaluations over a year were conducted in an endemic area of leishmaniasis in the state of Quintana Roo, Mexico. A randomized-block design was implemented in study area with tropical rainforest vegetation. The study design utilized 4 transects with 11 trap types: 1) Centers for Disease Control and Prevention (CDC) light trap with incandescent bulb (CDC-I), 2) CDC light trap with blue light-emitting diodes (LEDs) (CDC-B), 3) CDC light trap with white LEDs (CDC-W), 4) CDC light trap with red LEDs (CDC-R), 5) CDC light trap with green LEDs (CDC-G), 6) Disney trap, 7) Disney trap with white LEDs, 8) sticky panels, 9) sticky panels with white LEDs, 10) delta-like trap, and 11) delta-like trap with white LEDs. A total of 1,014 specimens of 13 species and 2 genera (Lutzomyia and Brumptomyia) were collected. There were significant differences in the mean number of sand flies caught with the 11 traps; CDC-I was (P  =  0.0000) more effective than the other traps. Other traps exhibited the following results: CDC-W (17.46%), CDC-B (15.68%), CDC-G (14.89%), and CDC-R (14.30%). The relative abundance of different species varied according to trap types used, and the CDC-I trap attracted more specimens of the known vectors of Leishmania spp., such as like Lutzomyia cruciata, Lu. shannoni, and Lu. ovallesi. Disney trap captured more specimens of Lu. olmeca olmeca. Based on abundance and number of species, CDC light traps and Disney traps appeared to be good candidates for use in vector surveillance programs in this endemic area of Mexico.

An Evaluation of Light-Emitting Diode (LED) Traps at Capturing Phlebotomine Sand Flies (Diptera: Psychodidae) in a Livestock Area in Brazil

A study to evaluate the use of light-emitting diodes (LEDs) as an attractant for phlebotomine sand flies at two animal pens in a livestock area in Brazil was performed. Light-suction traps were operated overnight with the following light sources: green, blue, and incandescent (control) lights. In total, 22 individual collections were made at each site and 44 with each trap type. In total, 2,542 specimens belonging to 14 phlebotomine species were collected. The most abundant species in the light traps were Nyssomyia whitmani, Evandromyia evandroi, Micropygomyia goiana, Lutzomyia longipalpis, and Bichromomyia flaviscutellata Taking the two sites together, the green-LED light was the most attractive, followed by the blue and incandescent lights, and the difference between the green-LED and the control was statistically significant. Most species were green-biased at both sites, but some species-specific differences were observed. However, even with these differences, the standard incandescent light was outcompeted by LEDs. The green-LED-biased response observed in the present study, together with numerous advantages in favor of LEDs, suggests that the green-LED light source can be used as an effective substitute for the currently used incandescent bulb in monitoring traps for phlebotomine sand flies in Brazil.

Evaluation of light-emitting diodes as attractant for sandflies (Diptera: Psychodidae: Phlebotominae) in northeastern Brazil

Hoover Pugedo light traps were modified for use with green and blue-light-emitting diodes to trap phlebotomine sandflies in northeastern Brazil. A total of 2,267 specimens belonging to eight genera and 15 species were sampled. The predominant species were Nyssomyia whitmani(34.41%) and Micropygomyia echinatopharynx(17.25%).The green LED trap prevailed over the blue and control lights; however, no statistically significant difference could be detected among the three light sources. Even without statistical significance, we suggest using LEDs as an attractant for the capture of sandflies because of several advantages over the conventional method with incandescent lamps.

Performance of light-emitting diode traps for collecting sand flies in entomological surveys in Argentina

The performance of two light-emitting diode traps with white and black light for capturing phlebotomine sand flies, developed by the Argentinean Leishmaniasis Research Network (REDILA-WL and REDILA-BL traps), were compared with the traditional CDC incandescent light trap. Entomological data were obtained from six sand fly surveys conducted in Argentina in different environments. Data analyses were conducted for the presence and the abundance of Lutzomyia longipalpis, Migonemyia migonei, and Nyssomyia whitmani (106 sites). No differences were found in presence/absence among the three types of traps for all sand fly species (p>0.05). The collection mean of Lu. longipalpis from the REDILA-BL didn´t differ from the CDC trap means, nor were differences seen between the REDILA-WL and the CDC trap collection means (p>0.05), but collections were larger from the REDILA-BL trap compared to the REDILA-WL trap (p<0.05). For Mg. migonei and Ny. whitmani, no differences were found among the three types of traps in the number of individuals captured (p>0.05). These results suggest that both REDILA traps could be used as an alternative capture tool to the original CDC trap for surveillance of these species, and that the REDILA-BL will also allow a comparable estimation of the abundance of these flies to the CDC light trap captures. In addition, the REDILA-BL has better performance than the REDILA-WL, at least for Lu. longipalpis.

Temporal distribution and behaviour of sand flies (Diptera: Psychodidae) in a cutaneous leishmaniasis focus of the Kani Tribe settlements in the Western Ghats, India

The temporal distribution of sand flies in relation to environmental factors was studied in the Kani tribe settlements located on the southernmost part of the Western Ghats, Kerala, India, between June 2012 and May 2013. This area is known for occurrence of cutaneous leishmaniasis (CL) cases. Employing hand-held aspirator, light trap and sticky-trap collection methods, a total of 7874 sand fly specimens, comprising 19 species was collected. Sergentomyia baghdadis was predominant species, followed by Phlebotomus argentipes. Sand fly abundance was significantly higher indoors (χ(2)=9241.8; p=0.0001) than outdoors. Mean density of P. argentipes in human dwellings, cattle sheds and outdoors was 7.2±2.9, 27.33±21.1 and 0.64±0.2 females/per man-hour (MHR), respectively. No sand fly species other than P. argentipes was obtained from cattle sheds. Although, sand fly populations were prevalent throughout the year, their abundance fluctuated with seasonal changes. Multiple regression analysis with backward elimination indicated that the increase in precipitation and relative humidity contributed to a significant positive association with the increase in sand fly abundance, while the increase in temperature showed no association. Fully engorged female sand flies tested for blood meal source showed multiple host-blood feeding. Analysis of resting populations of sand flies collected from human shelters indicated that the populations were found maximum on interior walls at 6-8 and >8 ft height, including ceiling during summer (F=83.7, df=6, p=0.001) and at the lower half of the wall at 0 and 0-2 ft height, during monsoon season (F=41.4, df=6, p=0.001). In cooler months, no preference to any height level (F=1.67, df=6, p=0.2) was observed. Proportion of females sand flies with Sella's classification of abdominal stages, namely full-fed, half-gravid and gravid females did not vary significantly (t=1.98, p=0.13827) indoors, confirming their endophilic behaviour. Risk of CL transmission in these tribal settlements is discussed.

Phlebotomus papatasi SP15: mRNA expression variability and amino acid sequence polymorphisms of field populations

Background

The Phlebotomus papatasi salivary protein PpSP15 was shown to protect mice against Leishmania major, suggesting that incorporation of salivary molecules in multi-component vaccines may be a viable strategy for anti-Leishmania vaccines.

Methods

Here, we investigated PpSP15 predicted amino acid sequence variability and mRNA profile of P. papatasi field populations from the Middle East. In addition, predicted MHC class II T-cell epitopes were obtained and compared to areas of amino acid sequence variability within the secreted protein.

Results

The analysis of PpSP15 expression from field populations revealed significant intra- and interpopulation variation.. In spite of the variability detected for P. papatasi populations, common epitopes for MHC class II binding are still present and may potentially be used to boost the response against Le. major infections.

Conclusions

Conserved epitopes of PpSP15 could potentially be used in the development of a salivary gland antigen-based vaccine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-0914-2) contains supplementary material, which is available to authorized users.

Response of the sand fly Phlebotomuspapatasi to visual, physical and chemical attraction features in the field

In this study, 27 CDC traps were modified with various attractive features and compared with a CDC trap with no light source or baits to evaluate the effects on attraction to Phlebotomus papatasi (Scopoli) north of the Dead Sea near Jericho. Attractive features included CO2, lights, colored trap bodies, heat, moisture, chemical lures and different combinations of the same. Traps were placed 20m apart and rotated from one trap location to the next after 24h trapping periods. The most significant attractive feature was CO2, which attracted more sand flies than any other feature evaluated. Ultraviolet light was the next most attractive feature, followed by incandescent light. When evaluated alone, black or white trap bodies, heat and moisture, all influenced trap catch but effects were greater when these attractive features were used together. The results of this study suggest that traps with CO2 and UV light could be used in batteries as control interventions if suitable CO2 sources become available.

Mosquito fauna of the Guapiaçu Ecological Reserve, Cachoeiras de Macacu, Rio de Janeiro, Brazil, collected under the influence of different color CDC light traps

The objective of the present study was to identify mosquito fauna and to evaluate whether different light bulb colors influence the attraction of light traps in the Guapiaçu Ecological Reserve. Samples were obtained monthly during the period of February, 2012 to January, 2013. Centers for Disease Control (CDC) light traps with incandescent light bulbs and LED (ultraviolet, blue, green, and red) bulbs were utilized. In total, 8,170 specimens were captured, including 59 species. The presence of Anopheles nimbus (Theobald 1902) and Orthopodomyia fascipes Coquillet 1906 were recorded for the first time in the state of Rio de Janeiro. The green LED trap attracted the highest number of specimens and presented the highest diversity and mosquito average. The blue and green LED traps attracted the highest number of species. However, the differences between lights were not significant. The most common species were Coquillettidia juxtamansonia (Chagas 1907), Culex declarator Dyar and Knab 1906, and Culex ribeirensis Forattini and Sallum 1985.

Field Evaluation of Different Wavelengths Light-Emitting Diodes as Attractants for Adult Aleurodicus dispersus Russell (Hemiptera: Aleyrodidae)

In recent years, light traps with light-emitting diodes (LEDs) have been widely used in integrated pest management. The spiralling whitefly, Aleurodicus dispersus Russell, a highly invasive pest which causes heavy damage to fruit trees and ornamental plants, exhibits positive phototaxis, and light trap is the most appropriate tool for monitoring. We evaluated the use of LEDs as an inexpensive light source and examined the relationship between the captured number and the population density of adult A. dispersus in the field. We found that the violet (405 nm) LED traps captured the most adults of A. dispersus, and the captured numbers were significantly higher than those of blue (460 nm), green (520 nm), yellow (570 nm), and red (650 nm) LED traps. The adults of A. dispersus captured by light traps equipped with violet LEDs and smeared with liquid paraffin had a significant positive correlation with the population density of adult A. dispersus in a guava orchard, with a correlation coefficient of 0.828. In general, the light traps with 15 violet LED bulbs hung into 550-mL plastic bottles and smeared with liquid paraffin were the portable devices for attraction of adult A. dispersus. The results have potential use for improving the efficiency of light traps at attracting and trapping the adult spiralling whitefly.

Influence of trap design on upwind flight behavior and capture of female grape berry moth (Lepidoptera: Tortricidae) with a kairomone lure

Oil-coated clear panel traps baited with a host plant-based kairomone lure have successfully been used for monitoring female grape berry moth, Paralobesia viteana (Clemens) (Lepidoptera: Tortricidae), but low capture rates as well as difficulty in servicing these traps makes them unsuitable for commercial use. We compared the performance of different trap designs in a flight tunnel and in a vineyard by using a 7-component synthetic kairomone blend, with a focus on trap visual cues. In flight tunnel experiments, a clear delta trap performed better than other traps. When we tested clear delta, green delta, or clear wing traps baited with a cut grape shoot, >50% of female grape berry moths made complete upwind flights. However, the clear delta trap was the only design that resulted in female moths entering the trap. Similar results were observed when females were tested with different traps (clear delta, green delta, white delta, clear wing, or green wing traps) baited with the kairomone lure. Adding a visual pattern that mimicked grape shoots to the outside surface of the clear delta trap resulted in 66% of the females that made upwind flights entering the trap. However, the positive effect of adding a visual pattern to the trap was not observed in a vineyard setting, where clear delta traps with or without a visual pattern caught similar numbers of females. Still, the number of male and female grape berry moths captured in clear delta traps with or without a visual pattern was not significantly different from the number of male and female grape berry moths captured in panel traps, suggesting that the use of these delta traps could be a less cumbersome alternative to oil-coated panel traps for monitoring female grape berry moth.

Environmental Engineering Approaches toward Sustainable Management of Spider Mites

Integrated pest management (IPM), which combines physical, biological, and chemical control measures to complementary effect, is one of the most important approaches to environmentally friendly sustainable agriculture. To expand IPM, we need to develop new pest control measures, reinforce existing measures, and investigate interactions between measures. Continued progress in the development of environmental control technologies and consequent price drops have facilitated their integration into plant production and pest control. Here I describe environmental control technologies for the IPM of spider mites through: (1) the disturbance of photoperiod-dependent diapause by artificial light, which may lead to death in seasonal environments; (2) the use of ultraviolet radiation to kill or repel mites; and (3) the use of water vapor control for the long-term cold storage of commercially available natural enemies. Such environmental control technologies have great potential for the efficient control of spider mites through direct physical effects and indirect effects via natural enemies.

Trapping of Rift Valley Fever (RVF) vectors using light emitting diode (LED) CDC traps in two arboviral disease hot spots in Kenya

BACKGROUND

Mosquitoes' response to artificial lights including color has been exploited in trap designs for improved sampling of mosquito vectors. Earlier studies suggest that mosquitoes are attracted to specific wavelengths of light and thus the need to refine techniques to increase mosquito captures following the development of super-bright light-emitting diodes (LEDs) which emit narrow wavelengths of light or very specific colors. Therefore, we investigated if LEDs can be effective substitutes for incandescent lamps used in CDC light traps for mosquito surveillance, and if so, determine the best color for attraction of important Rift Valley Fever (RFV) vectors.

METHODS

The efficiency of selected colored LED CDC light traps (red, green, blue, violet, combination of blue-green-red (BGR)) to sample RVF vectors was evaluated relative to incandescent light (as control) in a CDC light trap in two RVF hotspots (Marigat and Ijara districts) in Kenya. In field experiments, traps were baited with dry ice and captures evaluated for Aedes tricholabis, Ae. mcintoshi, Ae. ochraceus, Mansonia uniformis, Mn. africana and Culex pipiens, following Latin square design with days as replicates. Daily mosquito counts per treatment were analyzed using a generalized linear model with Negative Binomial error structure and log link using R. The incidence rate ratios (IRR) that mosquito species chose other treatments instead of the control, were estimated.

RESULTS

Seasonal preference of Ae.mcintoshi and Ae. ochraceus at Ijara was evident with a bias towards BGR and blue traps respectively in one trapping period but this pattern waned during another period at same site with significantly low numbers recorded in all colored traps except blue relative to the control. Overall results showed that higher captures of all species were recorded in control traps compared to the other LED traps (IRR < 1) although only significantly different from red and violet.

CONCLUSION

Based on our trapping design and color, none of the LEDs outcompeted the standard incandescent light. The data however provides preliminary evidence that a preference might exist for some of these mosquito species based on observed differential attraction to these light colors requiring future studies to compare reflected versus transmitted light and the incorporation of colored light of varying intensities.

Expression plasticity of Phlebotomus papatasi salivary gland genes in distinct ecotopes through the sand fly season

BACKGROUND

Sand fly saliva can drive the outcome of Leishmania infection in animal models, and salivary components have been postulated as vaccine candidates against leishmaniasis. In the sand fly Phlebotomus papatasi, natural sugar-sources modulate the activity of proteins involved in meal digestion, and possibly influence vectorial capacity. However, only a handful of studies have assessed the variability of salivary components in sand flies, focusing on the effects of environmental factors in natural habitats. In order to better understand such interactions, we compared the expression profiles of nine P. papatasi salivary gland genes of specimens inhabiting different ecological habitats in Egypt and Jordan and throughout the sand fly season in each habitat.

RESULTS

The majority of investigated genes were up-regulated in specimens from Swaymeh late in the season, when the availability of sugar sources is reduced due to water deprivation. On the other hand, these genes were not up-regulated in specimens collected from Aswan, an irrigated area less susceptible to drought effects.

CONCLUSION

Expression plasticity of genes involved with vectorial capacity in disease vectors may play an important epidemiological role in the establishment of diseases in natural habitats.

Comparison of three carbon dioxide sources on phlebotomine sand fly capture in Egypt

Lighted Centers for Disease Control and Prevention (CDC) light traps were baited with carbon dioxide (CO2) produced from three different sources to compare the efficacy of each in collecting phlebotomine sand flies in Bahrif village, Aswan Governorate, Egypt. Treatments consisted of compressed CO2 gas released at a rate of 250 ml/min, 1.5 kg of dry ice (replaced daily) sublimating from an insulated plastic container, CO2 gas produced from a prototype FASTGAS (FG) CO2 generator system (APTIV Inc., Portland, OR), and a CDC light trap without a CO2 source. Carbon dioxide was released above each treatment trap's catch opening. Traps were placed in a 4 x 4 Latin square designed study with three replications completed after four consecutive nights in August 2007. During the study, 1,842 phlebotomine sand flies were collected from two genera and five species. Traps collected 1,739 (94.4%) Phlebotomus papatasi (Scopoli), 19 (1.0%) Phlebotomus sergenti, 64 (3.5%) Sergentomyia schwetzi, 16 (0.9%) Sergentomyia palestinensis, and four (0.2%) Sergentomyia tiberiadis. Overall treatment results were dry ice (541) > FG (504) > compressed gas (454) > no CO2 (343). Total catches of P. papatasi were not significantly different between treatments, although CO2-baited traps collected 23-34% more sand flies than the unbaited (control) trap. Results indicate that the traps baited with a prototype CO2 generator were as attractive as traps supplied with CO2 sources traditionally used in sand fly surveillance efforts. Field-deployable CO2 generators are particularly advantageous in remote areas where dry ice or compressed gas is difficult to obtain.

Behavioral evidence for the presence of a sex pheromone in male Phlebotomus papatasi scopoli (Diptera: Psychodidae)

Phlebotomus papatasi (Diptera: Psychodidae) is the Old World sand fly vector of zoonotic cutaneous leishmaniasis caused by Leishmania major (Trypanosomatidae: Kinetoplastida), a debilitating and disfiguring protist parasitic disease prevalent throughout southern Mediterranean countries, the Middle East, as well as southern and eastern European countries, where it is regarded as a serious public health problem. Little is known of the mating ecology of P. papatasi, and, in particular, the role (if any) of pheromones is not known. In this laboratory- and field-based study, we have shown that a male-produced sex pheromone exists in P. papatasi. Young female P. papatasi are attracted to the headspace volatiles of small groups of males, males and females together, but not females alone. Males were not attracted to males, females, or mixed groups of males and females in the laboratory. Larger groups of males or males and females together were repellent in the laboratory study. Field experiments showed that Centers for Disease Control (CDC) light traps baited with small groups of males and females together were attractive to females, but not males. CDC traps baited with large groups of males and females together caught significantly fewer females and males than the control traps; however, the proportion of females caught compared with males overall was much higher than with CDC traps baited with small numbers of males and females. These results suggest that females may be attracted in preference to males to the vicinity of the baited traps and are highly sensitive to the concentration of male pheromone. It also suggests that P. papatasi mating behavior is fundamentally different from that of Lutzomyia longipalpis, where large mating aggregations of males and females occur.

Comparative efficacy of small commercial traps for the capture of adult Phlebotomus papatasi

We tested the performance of ten commercial mosquito traps with varying attractive features, against three CDC traps (an unlit model 512, an incandescently lit model 512, and a UV lit model 1212) as well as simple sticky paper, for their ability to attract and capture Phlebotomus papatasi in Israel. The commercial traps tested were the Sentinel 360, the Combo Trap, the Mega Catch Premier, the Bug Eater, the EcoTrap, the Galaxie Power-Vac, the Biter Fighter, the Black Hole, the Mosquito Trap, the Mosquito Catcher, the Sonic Web, the Solar Pest Killer, and a Bug Zapper. The four best performing traps with the highest nightly catches were the Sentinel 360 (85.96 ±19.34), the Combo Trap (70.00±7.78), the Mega Catch Premier (51.93±1.82) and the UV lit CDC 1212 trap (47.64±3.43). Five traps--the Mosquito Trap, the Mosquito Catcher, the Sonic Web, the Solar Pest Killer, and the Bug Zapper--performed exceptionally poorly, catching an average of less than two sand flies per day. To our knowledge, this is the first comprehensive attempt to evaluate commercial traps for their effectiveness in catching sand flies, and we show here that some traps that have been effective in catching mosquitoes are also effective in catching sand flies.