Comparison of several different trapping methods for Culicoides variipennis (Diptera: Ceratopogonidae)

When battery operated CDC miniature incandescent and black light traps (with and without light bulbs) were operated with and without CO2, the rank of trap effectiveness for total numbers of female Culicoides variipennis caught was: black light plus CO2; CO2-baited trap without light bulb; black light without CO2; incandescent light plus CO2 and incandescent light without CO2. In 1983, the black light trap plus CO2 caught significantly more males and females than any other traps, and the incandescent light trap without CO2 caught significantly fewer females than any other traps. There were significant differences also in times gnats were collected, as well as in the gonotrophic condition of females caught in traps and that different traps caught different physiological/reproductive segments of the population. All catches revealed that gravid females began flying only a few min before sunset and peaked in the 1st h after sunset. Because it caught significantly larger numbers of females than other traps and because it was selectively attractive to gravid and parous females, the black light trap would be the trap of choice when large numbers of parous females are desired in arbovirus isolation studies.     

Evaluation of three traps for sampling Aedes polynesiensis and other mosquito species in American Samoa

The efficacy of the recently developed BG-Sentinel mosquito trap baited with BG-Lure (a combination of lactic acid, ammonia, and caproic acid) was evaluated in American Samoa against the omnidirectional Fay-Prince trap and the Centers for Disease Control and Prevention (CDC) light trap, both baited with carbon dioxide. The BG-Sentinel trap captured the greatest number of the important filariasis and dengue vector Aedes (Stegomyia) polynesiensis at all 3 collection locations; however, its catch rate was not significantly different from that of the Fay-Prince trap at 2 of the 3 trapping locations. The CDC light trap caught very few Ae. polynesiensis. The Fay-Prince trap was more efficient than the other 2 traps for collecting Aedes (Aedimorphus) nocturnus, Aedes (Finlaya) spp., Culex quinquefasciatus, and Culex annulirostris. The efficacy and convenience of the BG-Sentinel suggest further research is warranted to evaluate its potential as a possible efficient and safe alternative to landing catches for sampling Ae. polynesiensis in research and control efforts against filariasis and dengue in the South Pacific.     

Efficacy of gravid traps in trapping Culex pipiens

Members of the Culex pipiens complex are principal vectors for West Nile virus (WNV) in the USA. Previous studies have shown that gravid traps might be more effective than CO2-baited traps in sampling for Cx. pipiens. We compared the efficacy of gravid traps manufactured by 3 different companies: Bioquip, Clarke, and J. W. Hock. All gravid traps have a similar setup to hold the oviposition attractant but differ in the way they collect the mosquitoes. The gravid trap manufactured by J. W. Hock Company trapped significantly more Cx. pipiens than the other traps. Because CO2-baited American Biophysics Corporation (ABC) traps are most often used by mosquito abatement agencies, we compared the efficacy of the Hock gravid trap with a CO2-baited ABC trap. There was no significant difference in the number of Cx. pipiens trapped between the Hock gravid and CO2-baited ABC trap. Because gravid traps predominantly attract previously bloodfed females (thereby aiding in WNV surveillance) and are logistically easier and cheaper to set up, we argue that the Hock gravid trap might be ideal for sampling Cx. pipiens populations.     

Comparison of mosquito trapping method efficacy for West Nile virus surveillance in New Mexico

As part of the West Nile virus surveillance program for the state of New Mexico, 13 sites along the Rio Grande River were sampled for mosquitoes during spring and summer 2003. We evaluated 3 different trapping procedures for their effectiveness at capturing selected species of mosquitoes. The 3 methods used were a dry ice-baited Centers for Disease Control and Prevention (CDC) light trap set 1.5 m above the ground (standard method), a CDC light trap suspended within the forest canopy, and a gravid trap set on the ground. Thirteen sites were sampled for 10 1-night periods biweekly from May through September. The relative numbers of captured Culex tarsalis, Cx. salinarius, Cx. quinquefasciatus, and Aedes vexans as well as the numbers of total recorded captures of all species were compared for each trapping method. Significant differences were observed for each species by location and by trapping method. Culex tarsalis was most commonly caught in canopy or standard CDC traps, especially in cottonwood bosque. Culex salinarius was found most frequently in association with marshy water, and was most often caught in gravid or standard light traps. Culex quinquefasciatus was captured almost exclusively in gravid traps within urban areas. Aedes vexans was primarily sampled in standard CDC light traps and found most frequently in wooded areas near floodplains. With the exception of Cx. Quinquefasciatus, no species was collected significantly more frequently in gravid or canopy traps than in the standard CDC light trap. Our findings do not support altering the methods currently used in New Mexico, namely, the use of 1.5-m CDC light traps and gravid traps. An increased use of gravid traps seems to be warranted in monitoring urban vector populations (specifically Cx. quinquefasciatus and Cx. salinarius) that may be involved in human transmission.     

Field comparison of novel and gold standard traps for collecting Aedes albopictus in Northern Virginia

Aedes albopictus is a potential West Nile virus bridge vector in Northern Virginia; however, information regarding its virus transmission dynamics is limited, as this species is not readily collected in existing traps. This study used 5 replicates of a 5 x 5 Latin square to evaluate the efficiency and effectiveness of 2 novel host-seeking mosquito traps (the BG-Sentinel and the Collapsible Mosquito Trap (CMT-20) in collecting Ae. albopictus, relative to a carbon dioxide (CO2)-baited Centers for Disease Control and Prevention (CDC) miniature light trap. When used with CO2, the BG-Sentinel (with BG-Lure) collected 33 times more female Ae. albopictus per 24-h trapping period than did the CO2-baited CDC light trap. Without CO2, the BG-Sentinel (with BG-Lure) still collected over 6 times as many female Ae. albopictus as the CO2-baited CDC trap. Both configurations of the BG-Sentinel were significantly more effective than the other traps. The BG-Sentinel was also significantly more efficient in collecting Ae. albopictus and collected a high proportion of this species, both with CO2 and without CO2. The CMT-20 (with SkinLure) collected significantly more Ae. albopictus when used with CO2 than without CO2, but did not collect significantly more Ae. albopictus than the CO2-baited CDC light trap. The proportion of Ae. albopictus collected in the CMT-20 with CO2 and without CO2 did not differ significantly from the proportion of Ae. albopictus collected in the CDC trap.     

New tools for surveillance of adult yellow fever mosquitoes: comparison of trap catches with human landing rates in an urban environment

A novel mosquito trapping system, the BG-Sentinel trap, was evaluated as a monitoring tool for adult Aedes aegypti in field tests in the city of Belo Horizonte, Brazil. Human landing/biting collections, a gas-powered CO2 trap, and a Fay-Prince trap with only visual cues serving as references to evaluate the efficacy of the new trap. The BG-Sentinel is a simple suction trap that uses upward-directed air currents as well as visual cues to attract mosquitoes. The trap was tested with a new dispenser system (BG-Lure) that releases artificial human skin odors and needs no CO2. In comparison with the two other traps, the BG-Sentinel caught significantly more Ae. aegypti. Although human landing rates were the highest, there was no significant difference between human landing rates and the capture rates of the BG-Sentinel trap. The finding indicates that the trap can be considered as an acceptable alternative to human landing/biting collections in the surveillance of adult host-seeking dengue vectors. The addition of BG-Lure to the gas-powered CO2 trap greatly increased its efficacy. This combination, however, was not significantly more effective than the BG-Sentinel without CO2. In a 6-month comparison between the BG-Sentinel and a sticky ovitrap for gravid females, the BG-Sentinel proved to be a far more efficient and sensitive tool to measure the density of Ae. aegypti populations.     

Field evaluation of a new surveillance trap in Sweden

Field tests were conducted to assess the effectiveness of American Biophysics Counterflow 2000 (CF2000) traps compared to CO2-baited Centers for Disease Control (CDC) miniature traps at a site in central Sweden. Adult mosquitoes representing 17 species and 6 genera were collected in July and August 1998. Although the 2 trap types did not differ significantly in total number of adult female mosquitoes collected, CF2000 traps captured a greater diversity of mosquito species and significantly more adult males than did CDC traps. Interspecific differences in capture rates and interactions between trap type and location also were observed.     

A two-year evaluation of elevated canopy trapping for Culex mosquitoes and West Nile virus in an operational surveillance program in the northeastern United States

The effectiveness of CO2-baited Centers for Disease Control and Prevention miniature light traps elevated in the tree canopy (approximately 7.6 m) was compared with light traps placed at ground level (approximately1.5 m) and grass-sod infused gravid traps for collecting Culex pipiens, Culex restuans, and Culex salinarius and detecting West Nile virus (WNV) activity in an operational surveillance program that encompassed 12 ecologically diverse sites in Connecticut in 2004 and 2005. More than twice as many Cx. pipiens were collected on average in light traps suspended in the tree canopy than in either light or gravid traps placed at ground level. This difference was generally restricted to those collection sites where markedly greater numbers of Cx. pipiens were collected with all trapping methods but was not associated with site-specific urbanization indices. Culex restuans was not preferentially attracted to light traps suspended in the tree canopy. No differences in the overall abundance of this species were recorded with either of the 2 trapping procedures, but both light traps were more effective than the gravid traps. Culex salinarius was significantly more attracted to ground-based light traps than traps suspended in the tree canopy, while gravid traps were ineffective at all sites regardless of the level of urbanization or any other specific land-use characteristic. CO2-baited light traps placed in the tree canopy were generally superior to ground-based light traps for detecting WNV in Cx. pipiens. West Nile virus-infected females were collected more regularly, and the frequency of infected pools was significantly greater. Twofold higher minimum field infection rates (maximum likelihood estimation [MLE] = 6.7 vs. 3.0 per 1,000 mosquitoes) were also recorded from canopy collections of this species, and virus was detected in canopy-collected females several weeks before it was detected in collections from light traps at ground level. We conclude that the use of CO2-baited light traps placed in the tree canopy for targeted trapping of Cx. pipiens and subsequent detection of WNV are likely to yield better overall results than light traps placed at ground level in this region of the northeastern United States. The virus isolation data obtained from Cx. pipiens collected in gravid traps compared favorably both temporally and spatially with results from canopy trap collections. There were no significant differences in the overall frequency of WNV-infected pools or MLEs for Cx. pipiens, but fewer total WNV isolations were made from Cx. pipiens collected in the gravid traps and virus was detected more infrequently. Results reaffirmed the utility of gravid traps as effective surveillance tools for detection of WNV in Cx. pipiens in the northeastern United States. However, findings also demonstrated that CO2-baited light traps placed in the tree canopy provided more consistent results where weekly detection of virus amplification is a critical objective. The comparative effectiveness of ground- and canopy-based light traps for detection of WNV-infected Cx. restuans and Cx. salinarius was inconclusive owing to the limited number of virus isolations that were made from these species during the 2 years of study. However, WNV virus isolations were made several weeks earlier and more frequently from Cx. restuans collected in traps placed in the canopy rather than at ground level in 2004. Results support the view that ground-based light traps are more effective for detection of WNV in Cx. salinarius.     

Laboratory evaluation of mosquito traps baited with a synthetic human odor blend to capture Aedes aegypti

A synthetic blend of chemicals comprising volatiles released by the human body has been shown to be an effective attractant for female Aedes aegypti in olfactometer bioassays with laboratory-reared mosquitoes. We report the laboratory evaluation of Ae. aegypti response to a synthetic blend tested with 4 types of mosquito traps (CDC model 512, CDC model 1012, CFG, and Fay-Prince traps). Aedes aegypti females were attracted significantly by the blend. The higher release rate of attractant (320.2 +/- 10.71 mg/h) more efficiently attracted mosquitoes than the lower release rate (42.0 +/- 2.3 mg/h). Although both the Fay-Prince and CFG traps caught higher number of mosquitoes than the other traps, only the CFG trap caught a statistically significant greater number of mosquitoes. The results suggest that the synthetic blend is effective in attracting Ae. aegypti females under controlled laboratory conditions (i.e., a closed system). Further studies are needed to evaluate the efficacy of this blend in baited traps under field conditions.     

Comparisons of light traps for monitoring adult Culicoides variipennis (Diptera: Ceratopogonidae)

From 1984 to 1986 tests were conducted to evaluate 4 trap types (ABADRL baffle trap, New Jersey trap, CDC trap, and updraft trap) with or without an incandescent light source, a suction fan or dry ice (as a source of CO2) for sampling adult Culicoides variipennis. The fewest flies were caught in the CDC and updraft traps. The New Jersey trap with suction, a strong light source and dry ice caught most flies, due to a significant increase in nulliparous females. The same New Jersey trap without dry ice caught the highest proportion of flies that had taken at least one bloodmeal. This trap would therefore be recommended for use in trapping for virus assay under epizootic conditions.     

Correlation of Aedes sierrensis captures at human sentinels with CO2-baited Fay-Prince and duplex cone traps.

The efficiency of the duplex cone and Fay-Prince traps for monitoring adult male and female Aedes sierrensis was evaluated at 3 field sites in California. The numbers of females captured by both types of traps were significantly correlated with human sentinel collections. The Fay-Prince trap captured more Ae. sierrensis females than the duplex cone trap and was a better tool for estimating female activity levels. There was no significant correlation between the number of males captured in Fay-Prince traps and at humans. Male numbers in duplex cone trap collections explained only 27% of the variation in the number of males collected at sentinels, suggesting that neither trap is a robust tool for estimating male activity around humans.     

Effectiveness of five methods for sampling adult Culex mosquitoes in rural and urban habitats in San Bernardino County, California

The comparative effectiveness of NJ light traps, CO2-baited traps, walk-in red boxes, high-intensity light traps and gravid traps for sampling adult Culex mosquitoes for arbovirus surveillance was compared at rural dairy and residential urban habitats near Chino, California. Culex quinquefasciatus was the most abundant of the 3 species present comprising 94.9% of the 23,159 mosquitoes collected, followed by Cx. peus (4.2%) and Cx. tarsalis (0.9%). Female mosquitoes of all species were most abundant in CO2-baited traps at both urban and rural environments. Males were collected most effectively by walk-in red boxes in rural, but not urban, environments. More parous females were collected by CO2-baited traps at urban than rural habitats; however, 70-79% of all females were nulliparous and had never blood fed. These data point out the potential insensitivity of the current sampling methodology in monitoring mosquito arbovirus infection rates.     

Evaluation of selected modifications to CO2 and infusion-baited mosquito traps in Urbana, Illinois

The efficacy of granular media CO2 sachets used in conjunction with Center for Disease Control and Prevention (CDC) miniature light traps with light bulbs removed and modifications of bucket size and color to infusion-baited gravid traps was assessed from June through August of 2004 in Urbana, IL. The sachet packets caught significantly more mosquitoes and mosquito species compared with traps containing no CO2 bait; however, they also caught significantly fewer mosquitoes and fewer mosquito species compared with traps baited with dry ice. Pairing CO2-generating sachets with various dosages of octenol did not significantly increase the numbers of mosquitoes or mosquito species compared with traps baited only with sachets. When comparing modifications in the bucket size of gravid traps, the larger bucket (1,645-cm2 surface area holding about 5.3 liters of infusion) caught significantly more mosquitoes compared with the smaller bucket (759-cm2 surface area holding about 3.0 liters of infusion). Bucket color (green, blue, or black) did not affect the total number of mosquitoes caught.     

Evaluation of carbon dioxide- and 1-octen-3-ol-baited Centers for Disease Control Fay-Prince traps to collect Aedes albopictus

During the summer of 2001, field studies were performed to evaluate the effects of carbon dioxide (CO2) and 1-octen-3-ol (octenol) on the ability to collect Aedes albopictus with Centers for Disease Control (CDC) Fay-Prince traps. Results from these studies indicated that Ae. albopictus is significantly more attracted to CO2- or CO2 + octenol-baited CDC Fay-Prince traps than unbaited or octenol-baited traps. However, the difference between the responses to CO2 and CO2 + octenol was not statistically different, indicating that CO2 is driving the response of Ae. albopictus to CDC Fay-Prince traps.     

Effects of trap design and CO2 presentation on the measurement of adult mosquito abundance using Centers for Disease Control-style miniature light traps

Centers for Disease Control miniature light traps augmented with CO2 provide an effective method of monitoring Culex abundance and may provide a useful supplement to New Jersey light traps used by the California Mosquito Surveillance Program. To assist in standardizing sampling protocols, the present research compared the catch of adult mosquitoes collected using 4 trap designs and 3 CO2 presentation methods. When augmented with dry ice, the Arbovirus Field Station (AFS) trap (consisting of a 3-in. fan mounted into a white polyvinyl chloride pipe and operated without a light source or rain shield) collected as many or more Culex females than similar traps purchased from John W. Hock and American Biophysics, or a trap with a 4.25-in. 2-bladed fan constructed by the Orange County Vector Control District (similar to the Encephalitis Virus Surveillance model distributed by Bioquip). Few blooded or gravid females and males were collected, indicating that CO2 released from the dry ice and not light probably was the primary attractant. Catch of Culex tarsalis females in traps baited with CO2 released at 0.5-1.5 liters/min from gas cylinders was significantly greater than in traps baited with dry ice, even though the CO2 release rates from the dry ice at dusk probably were comparable to that released from the cylinders and averaged 0.4-0).5 liters/min for the night. Traps baited with 0.5 liters/ min of CO2 gas released in 15 3- or 2-sec bursts per hour collected the fewest mosquitoes. In all experiments, trap location effects were significant and accounted for as much variability in catch size as trap design or CO2 presentation. Sampling efficiency of all trap designs or CO2 presentations were consistent over time, space, and different levels of mosquito abundance.     

Comparative effectiveness of three adult mosquito sampling methods in habitats representative of four different biomes of California.

The effectiveness of New Jersey (NJ) light, dry ice baited, and gravid female traps for collecting adult mosquitoes was compared at representative habitats in the Coachella, San Joaquin, and Sacramento valleys and the Los Angeles basin of California. The NJ light traps effectively sampled Anopheles freeborni, Culex tarsalis, Psorophora columbiae, and several Aedes when abundance was high in rural areas with minimal competitive illumination. Dry ice-baited encephalitis virus surveillance or CDC style traps collected significantly more females of most species at most localities than did NJ light traps, regardless of background illumination. The Cummings modification of the Reiter gravid female trap baited with a bulrush (Schoenoplectus) infusion was the best method for collecting Culex pipiens complex females in most habitats. In the Los Angeles basin, gravid traps baited with bulrush infusion collected, on average, 4.5 times more Culex quinquefasciatus females than did traps baited with the Reiter infusion. The bulrush infusion in combination with the Cummings trap design seemed to provide resting site cues and collected males as well as empty and bloodfed females. Mosquito surveillance programs in California should include the systematic operation of dry ice-baited and gravid female traps to improve surveillance sensitivity for selected species in appropriate habitats.     

Commercial mosquito trap and gravid trap oviposition media evaluation, Atlanta, Georgia

Field trials evaluating the effectiveness of selected gravid trap oviposition media and commercially available mosquito traps were conducted in southern Fulton County (Atlanta), GA, from June 9 to June 18 and June 24 to July 4, 2002, respectively. Total number of mosquitoes and number of each species captured during the tests were compared using a Latin square design. For the gravid trap infusion media, significant differences were found for total number of mosquitoes collected where sod > or = hay > or = hay side-by-side diluted hay > dilute hay side-by-side hay > or = oak > diluted hay. Only Aedes albopictus (oak), Culex quinquefasciatus (sod and both concentrated hay infusions), and Culex restuans (sod) were captured in significantly greater numbers using a particular infusion. Significant differences for the total number of mosquitoes collected were also observed in the commercial mosquito traps such that the gravid trap > ultra violet up-draft > or = Mosquito Magnet Pro > or = omnidirectional Fay-Prince trap with CO2 > up-draft CDC-style with CO2 > or = CDC-style with CO2. Significant differences in numbers collected among traps were noted for several species, including Aedes vexans, Aedes albopictus, Cx. quinquefasciatus, Cx. restuans, and Culex salinarius. Results from these field trap and infusion evaluations can enhance current surveillance efforts, especially for the primary vectors of West Nile virus and other arboviruses.     

Urbanization and the efficiency of carbon dioxide and gravid traps for sampling Culex quinquefasciatus.

The efficiency of gravid and CO2 traps for sampling female Culex quinquefasciatus was evaluated along 2 parallel 6.4 km long urban (high housing density) to rural (low housing density) transects in east Bakersfield, Kern County, CA. There were no significant differences in the number of female Cx. quinquefasciatus collected by gravid traps within urban and rural zones. The number of females collected per trap night ranged from 6.8 to 15.5. The number of females collected by CO2 traps increased significantly from 1.4 to 3.1 per trap night in urban to 31.8 to 111.2 per trap night in rural zones and was inversely correlated with housing density. These results indicate that female Cx. quinquefasciatus were effectively sampled by gravid traps in urban subdivisions and by CO2 traps in rural mixed agricultural areas.     

A comparison of seven traps used for collection of Aedes albopictus and Aedes aegypti originating from a large tire repository in Harris County (Houston), Texas

Among 7 traps tested, significantly higher (P < 0.01) mean numbers of Aedes albopictus (269) and Aedes aegypti (55) females were collected within the Mosquito Magnet Liberty trap compared with the remaining traps. The second highest mean captures for both species were obtained from omnidirectional Fay-Prince (77 Ae. albopictus) and Dragonfly (13 Ae. aegypti) traps, which were not significantly different (P > 0.01) from an experimental moving-target trap that produced mean captures of 40 Ae. albopictus and 6 Ae. aegypti (alpha = 0.01). In terms of Ae. albopictus capture, no significant differences (P > 0.01) existed between Dragonfly, CDC without light (CDC -), and CDC with light (CDC +) captures, which were significantly different (P < 0.01) from Mosquito Deleto. No statistical significance existed between moving-target, omnidirectional, CDC +, CDC -, and Mosquito Deleto traps in terms of Ae. aegypti capture (P > 0.01), individual trap positions, or number of Ae. albopictus and Ae. aegypti females collected throughout the 21-day test (P > 0.05). Mosquito Magnet Liberty collected 7,208 Ae. albopictus, 1467 Ae. aegypti, and 13 other species representing 5 genera, which comprised the largest total (9662) and percentage (62.5%) of mosquitoes collected by all traps combined. Omnidirectional and moving-target traps captured 1941 and 1050 Ae. albopictus, 138 and 220 Ae. aegypti, and 2171 (14.0%) and 1397 (9.0%) of the total mosquitoes captured by all traps, with 8 and 10 species representing 5 genera, respectively, included in these collections. The Dragonfly captured 476 Ae. albopictus, 376 Ae. aegypti, and 1008 total specimens (6.5%) representing 8 species and 4 genera in these collections. CDC + and CDC - traps collected nearly identical numbers of Ae. albopictus (431, 450) and Ae. aegypti (71, 71) with 537 (3.4%) and 551 (3.5%) total specimens, respectively. Eight species representing 5 genera were captured from CDC +, whereas CDC - captured 6 species representing 4 genera. Mosquito Deleto captured 118 mosquitoes, including 19 Ae. albopictus and 62 Ae. aegypti females (0.7%), with 6 species representing 4 genera. Battery-powered traps with contrasting color schemes and movement worked considerably better than stationary CDC miniatures without color or movement. Omnidirectional Fay-Prince and moving-target traps without octenol captured Ae. albopictus and Ae. aegypti females as frequently as some commercial traps. Additionally, costs incurred per mosquito trapped, future trap design, and important consumer-centered issues are briefly discussed.     

Selected mosquito vectors of West Nile virus: comparison of their ecological dynamics in four woodland and marsh habitats in Delaware

We compared human landing, CO2-baited light trap, CO2-baited Omni-Fay trap, and gravid trap collections of mosquitoes at 4 woodland and marsh sites with varied vegetative habitats in Delaware during summer 2001. Landing collections provided more consistent, but sometimes smaller, collection numbers than light traps. Proportions of parous mosquitoes were also higher in landing than in light trap or Omni-Fay collections about 65% of the time. Circadian feeding rhythms were observed for 3 suspected vector species selected on the basis of 1999-2000 laboratory vector competence data and their presence at local habitats. These species included Aedes vexans, Culex salinarius, and Cx. pipiens pipiens. Aedes vexans fed after dusk, primarily before 2200 h and again around dawn (0600-0700 h). Both Cx. salinarius and Cx. p. pipiens exhibited peak feeding activity after dusk and in predawn periods, as well as extended feeding periods up until midnight. Time of feeding is an important factor in evaluating vector-host associations and risks of human outbreaks.