Comparison of Mosquito Magnet and Biogents Sentinel Traps for Operational Surveillance of Container-Inhabiting Aedes (Diptera: Culicidae) Species

Do Aedes triseriatus Respect State Boundaries?: A Paucity of La Crosse Virus in the South Carolina Appalachian Mountains

Background: La Crosse virus is an important endemic public health concern in the North Carolina Appalachian Mountains; however, human incidence is not commonly noted in this region on the South Carolina side of the mountain range border. No relevant studies have been performed in South Carolina evaluating mosquito vector populations for La Crosse virus (LACV) infection; thus, a pilot mosquito surveillance study was executed in summer 2020. Material and Methods: Vector surveillance occurred at five South Carolina state parks bordering neighboring state endemic counties from May to August 2020. Collections were approved by the state park authority, as noted in Permit No. N-8-20. Results: All three competent mosquito vectors were collected during the study duration; however, these vectors were collected in low abundance: Aedes triseriatus (4.5% of all collected mosquitos); Aedes albopictus (2.0%); Aedes japonicus (1.4%). Principal mosquito vector specimens, Ae. triseriatus, were sent to Centers for Disease Control and Prevention for testing of LACV by real-time reverse transcription PCR-all were negative. Discussion: While entomologic evidence suggests low transmission risk for this arbovirus in the South Carolina Appalachian Mountain region, further eco-epidemiologic investigations are warranted to understand this endemicity variance within a relatively small geographic area.

Control methods for invasive mosquitoes of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Indonesia

The two invasive mosquito species in Indonesia are Aedes aegypti and Ae. albopictus. These mosquitoes are a serious nuisance to humans and are also the primary vectors of several foreign pathogens, such as dengue, Zika, and chikungunya viruses. Efforts must be made to reduce the possibility of mosquito bites and the potential for disease transmission. Given the invasion of these two Aedes species, this approach should be considered as part of an integrated strategy to manage them. This review discusses existing and developing control techniques for invasive Ae. aegypti and Ae. albopictus, with an emphasis on those that have been and are being used in Indonesia. Environmental, mechanical, biological (e.g., Bacillus thuringiensis and Wolbachia), and chemical (e.g., insect growth regulators and pyrethroids) approaches are discussed in this review, considering their effectiveness, sustainability, and control methods.

Mosquito Surveillance for West Nile Virus

Identifying the mosquitoes responsible for transmitting human disease-causing pathogens is of critical importance for effective control of mosquito-borne outbreaks. West Nile virus is often transferred by adult female mosquitoes in the genus Culex, which deposit eggs in a variety of aquatic habitats throughout the world. Herein we describe several methodological approaches to monitor these species in nature, as well as offering details for data collection and analysis.

An alien in Marseille: investigations on a single Aedes aegypti mosquito likely introduced by a merchant ship from tropical Africa to Europe

Control of invasive species relies partly on permanent surveillance at international points of entry. We report the exceptional trapping of one adult mosquito (Diptera: Culicidae) in the port of Marseille, France, in July 2018, during a routine survey conducted according to International Health Regulations. Morphological and molecular identification classified the specimen as a female Aedes (Stegomyia) aegypti (L.), vector of many arboviruses, absent from Europe and the Mediterranean rim since the 1950s. A world reference panel of approximately 23,000 genome-wide single nucleotide polymorphisms determined that the mosquito originated from Cameroon, west Africa. Cross-reference of this geographic location with boats traveling from Central Africa to Marseille during the trapping period suggests that the mosquito travelled within an identified merchant ship, a vehicles carrier connecting Douala, Cameroon to Marseille, France. This ship left Douala on June 25, 2018 and arrived 20 days later in Marseille on July 15. The mosquito was captured 350 m away from the dock. The interception of a propagule of an invasive species is a rare event that must be considered a priority to prevent its successful establishment.

Mosquito Attractants

Vector control and personal protection against anthropophilic mosquitoes mainly rely on the use of insecticides and repellents. The search for mosquito-attractive semiochemicals has been the subject of intense studies for decades, and new compounds or odor blends are regularly proposed as lures for odor-baited traps. We present a comprehensive and up-to-date review of all the studies that have evaluated the attractiveness of volatiles to mosquitoes, including individual chemical compounds, synthetic blends of compounds, or natural host or plant odors. A total of 388 studies were analysed, and our survey highlights the existence of 105 attractants (77 volatile compounds, 17 organism odors, and 11 synthetic blends) that have been proved effective in attracting one or several mosquito species. The exhaustive list of these attractants is presented in various tables, while the most common mosquito attractants - for which effective attractiveness has been demonstrated in numerous studies - are discussed throughout the text. The increasing knowledge on compounds attractive to mosquitoes may now serve as the basis for complementary vector control strategies, such as those involving lure-and-kill traps, or the development of mass trapping. This review also points out the necessity of further improving the search for new volatile attractants, such as new compound blends in specific ratios, considering that mosquito attraction to odors may vary over the life of the mosquito or among species. Finally, the use of mosquito attractants will undoubtedly have an increasingly important role to play in future integrated vector management programs.

Trap Comparison for Surveillance of the Western Tree Hole Mosquito (Diptera: Culicidae)

The western tree hole mosquito, Aedes sierrensis (Ludlow), is a common nuisance mosquito and vector of Dirofilaria immitis (Leidy), the etiologic agent of dog heartworm, in western North America. Here, we compare weekly mosquito collections made with Mosquito Magnet (MM) traps, Biogents Sentinel (BGS) traps, and Biogents Bowl (BGS Bowl) traps set in Salt Lake City, UT, from the start of June to mid-August 2017. We found the number of mosquitoes decreased with rainfall and temperature independently of trap type. The highest number of mosquitoes were caught by BGS traps baited with carbon dioxide (CO2) and BG lure, which collected 62% (n = 422) of all mosquitoes, followed by the MM at 31% (n = 213), and both the BGS and BG Bowl with BG lure had 3.5% (n = 24) each. Aedes sierrensis females were caught weekly at similar densities (mean ± SD) in BGS with CO2 and lure (1.17 ± 2.93) and the MM (1.17 ± 2.66) traps during the study period. Given that BGS with CO2 and lure traps have several operational advantages over MM traps, including a quicker setup, smaller size, and lower cost, we consider BGS with CO2 and lure traps as the best suited surveillance tool to detect and remove Ae. sierrensis in the western United States and similar settings throughout North America.

West Nile Virus Mosquito Vectors in North America

In North America, the geographic distribution, ecology, and vectorial capacity of a diverse assemblage of mosquito species belonging to the genus Culex determine patterns of West Nile virus transmission and disease risk. East of the Mississippi River, mostly ornithophagic Culex pipiens L. complex mosquitoes drive intense enzootic transmission with relatively small numbers of human cases. Westward, the presence of highly competent Culex tarsalis (Coquillett) under arid climate and hot summers defines the regions with the highest human risk. West Nile virus human risk distribution is not uniform geographically or temporally within all regions. Notable geographic 'hotspots' persist with occasional severe outbreaks. Despite two decades of comprehensive research, several questions remain unresolved, such as the role of non-Culex bridge vectors, which are not involved in the enzootic cycle, but may be involved in virus transmission to humans. The absence of bridge vectors also may help to explain the frequent lack of West Nile virus 'spillover' into human populations despite very intense enzootic amplification in the eastern United States. This article examines vectorial capacity and the eco-epidemiology of West Nile virus mosquito vectors in four geographic regions of North America and presents some of the unresolved questions.

Enhancing attraction of the vector mosquito Aedes albopictus by using a novel synthetic odorant blend

Background

The Asian tiger mosquito, Aedes albopictus, an increasingly relevant arboviral vector, has spread worldwide. However, currently available tools are limited in terms of effective monitoring of vector populations and accurate determination of the extent of viral transmission, especially before and during outbreaks. Therefore, it is essential to develop novel monitoring and surveillance tools, particularly those that target adult mosquitoes and enhance the trapping efficiency for Ae. albopictus.

Methods

A variety of human body odorants associated with different types of mosquito olfactory receptors were selected, and their attractiveness to Ae. albopictus was tested by a four-arm olfactometer. The optimal compatibility and proportion of the odorants, Mix-5, was observed via orthogonal design analyses. The attractiveness of Mix-5 to Ae. albopictus in the laboratory was assessed using Mosq-ovitraps and Electric Mosquito Killers. In the field, the effectiveness of generic BG-Lure, Mix-5 and a control treatment was compared with a baited Biogents Sentinel trap (BGS-trap) using a Latin square design.

Results

In the olfactometer experiments, the attractiveness of the selected candidate compounds at varying dilutions was poor when the individual compounds were used alone. The optimal combination, Mix-5, was generated based on orthogonal design analyses. In the laboratory, the average numbers of female Ae. albopictus mosquitoes attracted by the synthetic odorant blend Mix-5 were 27.00 and 27.50, compared with 12.00 and 14.83 for the control, when using Mosq-ovitraps and Electric Mosquito Killers, respectively. In the field, the average number of Ae. albopictus female mosquitoes trapped by Mix-5 was 9.67 females/trap, whereas the average numbers for BG-Lure and the control were 7.78 and 4.47, respectively. The lure also played an important role in attracting Culex quinquefasciatus mosquitoes, and the average numbers of Cx. quinquefasciatus female mosquitoes attracted by Mix-5, BG-Lure and the control were 18.78, 25.11 and 12.22, respectively.

Conclusions

A human odor-based bait blend was developed and exhibited enhanced effectiveness at attracting Ae. albopictus This blend can be used to monitor and trap dengue vector mosquitoes in Chinese cities.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3646-x) contains supplementary material, which is available to authorized users.

Field Trials to Evaluate the Effectiveness of the Biogents®-Sweetscent Lure in Combination with Several Commercial Mosquito Traps and to Assess the Effectiveness of the Biogents-Mosquitaire Trap with and Without Carbon Dioxide

A series of field experiments was conducted in Florida, California, and Louisiana in order to investigate whether adding the Biogents® (BG)-Sweetscent lure to several commercially available mosquito traps increases their Aedes albopictus catch rates and to evaluate the BG-Mosquitaire trap with and without CO₂. Adding the BG-Sweetscent to the SkeeterVac Bite-Guard SVE6211, MosClean UV LED (ultraviolet light-emitting diode), Flowtron® Galaxie PV 75, Dynatrap® DT2000XL, Bite Shield Protector, and Black Flag® BZ-40 increased their Ae. albopictus catch rates up to 4.2-fold. The catch rates of the BG-Mosquitaire and the BG-Sentinel did not differ significantly for Ae. aegypti and Culex quinquefasciatus. The BG-Mosquitaire without CO₂ and only with BG-Sweetscent caught 1.2 times more Ae. albopictus than the CO₂- and Lurex3-baited Mosquito Magnet® Patriot and 2.6 times more than the CO₂- and Sweetscent-baited SkeeterVac, respectively. The BG-Mosquitaire baited with Sweetscent and CO₂ collected 6.8 times more Ae. albopictus than the Mosquito Magnet Patriot and 11.9 times more than the SkeeterVac. We conclude that BG-Sweetscent increases the tiger mosquito catch rates of many commercially available mosquito traps. We proved that the BG-Mosquitaire is as efficient as the well-known BG-Sentinel and that it can outperform mosquito traps that are baited with propane-generated CO₂.

Comparison of Mosquito Abundance From Biogents Sentinel 2.0 Traps With and Without Rain Covers

Biogents Sentinel (BGS) traps have rapidly become a standard for adult Aedes aegypti surveillance. Several investigators have found that trap collections can be damaged easily by heavy dew or rain entering the trap intake port. In addition, water entering the trap may temporarily stop the fan, thus reducing the collection potential of the trap. We evaluated the effectiveness of a rain cover designed to minimize damage to mosquito trap collections from BGS 2.0 traps in a residential backyard in Jacksonville, FL. Rain covers consisted of white fiberglass 51-cm² sheets positioned 19, 29, and 39 cm above the air intake of the traps. One BGS trap did not have a rain cover and was used as a control standard for comparison. All traps were baited with the BG-Lure. Generally, traps with rain covers resulted in higher mosquito counts when compared with collections from uncovered traps. Overall mosquito abundance was greater from traps with the rain cover positioned at 29 cm, but this difference was not significantly different when compared with the other cover heights. Covers spaced 29 or 39 cm collected significantly more Culex quinquefasciatus compared with traps at 19 cm and no cover. Species diversity was greatest for BGS traps with the rain cover positioned at 29 cm followed by 39 cm, 19 cm, and no cover; however, differences in diversity among the traps, with or without covers, were not significant.

Evaluation of the Trapping Performance of Four Biogents AG Traps and Two Lures for the Surveillance of Aedes albopictus and Other Host-Seeking Mosquitoes

The BG-Sentinel® (BGS) trap has recently been redesigned for increased durability and ergonomic functionality, marketed as the BG-Sentinel 2® (BGS2). We evaluated the trapping performance of these 2 traps in addition to the BG-Sentinel prototype (BGSP), a model similar to the BGS2 that was beta tested in several US states in 2014, and the BG-SNAP (SNAP), which is a prototype revision of the BG-Mosquitito™. We also evaluated 2 new Biogents AG lures: the BG-Lure cartridge and BG-Sweetscent™, as they are granular formulations replacing the original mesh BG-Lure®. Evaluations were conducted between July and September 2015 under field conditions within a suburban area in southeastern Virginia. The 4 traps were compared with their respective lure systems (BGS, BGSP, and BGS2 with BG-Lure cartridge; SNAP with BG-Sweetscent). No significant differences were seen in total female mosquito collections among the 3 BG-Sentinel models. All 3 Sentinels collected significantly more female mosquitoes than the SNAP (P ≤ 0.009); BGS and BGS2 both collected significantly more Aedes albopictus females than the SNAP (P ≤ 0.02). The 2 lures were compared in both BGS2 and SNAP traps. Although both lures performed significantly better in the BGS2 trap (P ≤ 0.0003), there were no significant differences in number of mosquitoes or species composition collected with BG-Sweetscent and BG-Lure cartridge within the same trap type.

The Eye of the Tiger, the Thrill of the Fight: Effective Larval and Adult Control Measures Against the Asian Tiger Mosquito, Aedes albopictus (Diptera: Culicidae), in North America

The Asian tiger mosquito, Aedes albopictus (Skuse), is a highly invasive container-inhabiting species with a global distribution. This mosquito, similar to other Stegomyia species such as Aedes aegypti (L.), is highly adapted to urban and suburban areas, and commonly oviposits in artificial containers, which are ubiquitous in these peridomestic environments. The increase in speed and amount of international travel and commerce, coupled with global climate change, have aided in the resurgence and expansion of Stegomyia species into new areas of North America. In many parts of their range, both species are implicated as significant vectors of emerging and re-emerging arboviruses such as dengue, chikungunya, and now Zika. Although rapid and major advances have been made in the field of biology, ecology, genetics, taxonomy, and virology, relatively little has changed in the field of mosquito control in recent decades. This is particularly discouraging in regards to container-inhabiting mosquitoes, because traditional integrated mosquito management (IMM) approaches have not been effective against these species. Many mosquito control programs simply do not possess the man-power or necessary financial resources needed to suppress Ae. albopictus effectively. Therefore, control of mosquito larvae, which is the foundation of IMM approaches, is exceptionally difficult over large areas. This review paper addresses larval habitats, use of geographic information systems for habitat preference detection, door-to-door control efforts, source reduction, direct application of larvicides, biological control agents, area-wide low-volume application of larvicides, hot spot treatments, autodissemination stations, public education, adult traps, attractive-toxic sugar bait methods, lethal ovitraps, barrier-residual adulticides, hand-held ultra-low-volume adulticides, area-wide adulticides applied by ground or air, and genetic control methods. The review concludes with future recommendations for practitioners, researchers, private industry, and policy makers.

TrapTech R-Octenol Lure Does Not Improve the Capture Rates of Aedes albopictus (Diptera: Culicidae) and Other Container-Inhabiting Species in Biogents Sentinel Traps

Aedes albopictus (Skuse) and other container-inhabiting species have become important public health concerns due to the transmission of dengue, chikungunya, and Zika viruses. Effective surveillance is dependent on the ability to collect a sufficient number of mosquitoes for population monitoring and pathogen isolation. The Biogents Sentinel (BGS) trap supplied with a proprietary human skin lure has become the standard tool for container-inhabiting Aedes species collections worldwide. Recently, R-octenol, a single isomer of the well characterized mosquito attractant octenol, was shown to greatly improve the capture rate of some Aedes species when utilized with the Center for Disease Control and Prevention (CDC) light traps and Mosquito Magnet traps. This study evaluated the effectiveness of the TrapTech lure (TT lure), containing R-octenol, alone or in combination with the human skin lure in a BGS trap to capture Ae. albopictus and other species. BGS traps with human skin lures or a combination of the two lures collected approximately twice as many Ae. albopictus females compared to those with TT lures. Unlike previous studies, baiting BGS traps with TT lures did not result in increased diversity of mosquito species, or in higher numbers of other container-inhabiting Aedes species. Although human skin lures were clearly superior to TT R-octenol lures in BGS traps, R-octenol lures are more widely available and might still be used as an alternative lure, especially when Ae. albopictus populations are high.

Newly discovered population of Aedes japonicus japonicus (Diptera: Culicidae) in Upper Bavaria, Germany, and Salzburg, Austria, is closely related to the Austrian/Slovenian bush mosquito population

Background

The German mosquito surveillance instrument ‘Mueckenatlas’ requests the general public to collect and submit mosquito specimens. Among these, increasing numbers of individuals of invasive species have been registered. Specimens of the Asian bush mosquito Aedes japonicus japonicus submitted from German Upper Bavaria, where this species had not previously been recorded, triggered regional monitoring in mid-2015.

Methods

The search for Ae. j. japonicus breeding sites and developmental stages concentrated on cemeteries in the municipality of origin of the submitted specimens and, subsequently, in the whole region. A virtual grid consisting of 10 × 10 km² cells in which up to three cemeteries were checked, was laid over the region. A cell was considered positive as soon as Ae. j. japonicus larvae were detected, and regarded negative when no larvae could be found in any of the cemeteries inspected. All cells surrounding a positive cell were screened accordingly. A subset of collected Aedes j. japonicus specimens was subjected to microsatellite and nad4 sequence analyses, and obtained data were compared to individuals from previously discovered European populations.

Results

Based on the grid cells, an area of approximately 900 km² was populated by Ae. j. japonicus in Upper Bavaria and neighbouring Austria. Genetic analyses of microsatellites and nad4 gene sequences generated one genotype out of two previously described for Europe and three haplotypes, one of which had previously been found in Europe only in Ae. j. japonicus samples from a population in East Austria and Slovenia. The genetic analysis suggests the new population is closely related to the Austrian/Slovenian population.

Conclusion

As Ae. j. japonicus is well adapted to temperate climates, it has a strong tendency to expand and to colonise new territories in Central Europe, which is facilitated by human-mediated, passive transportation. The new population in Upper Bavaria/Austria is the seventh separate population described in Europe. According to our data, it originated from a previously detected population in eastern Austria/Slovenia and not from an introduction event from abroad. The dispersal and population dynamics of Ae. j. japonicus should be thoroughly surveyed, as this species is a potential vector of disease agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1447-z) contains supplementary material, which is available to authorized users.