Partners in diabetes epidemic: A global perspective

There is a recent increase in the worldwide prevalence of both obesity and diabetes. In this review we assessed insulin signaling, genetics, environment, lipid metabolism dysfunction and mitochondria as the major determinants in diabetes and to identify the potential mechanism of gut microbiota in diabetes diseases. We searched relevant articles, which have key information from laboratory experiments, epidemiological evidence, clinical trials, experimental models, meta-analysis and review articles, in PubMed, MEDLINE, EMBASE, Google scholars and Cochrane Controlled Trial Database. We selected 144 full-length articles that met our inclusion and exclusion criteria for complete assessment. We have briefly discussed these associations, challenges, and the need for further research to manage and treat diabetes more efficiently. Diabetes involves the complex network of physiological dysfunction that can be attributed to insulin signaling, genetics, environment, obesity, mitochondria and stress. In recent years, there are intriguing findings regarding gut microbiome as the important regulator of diabetes. Valid approaches are necessary for speeding medical advances but we should find a solution sooner given the burden of the metabolic disorder - What we need is a collaborative venture that may involve laboratories both in academia and industries for the scientific progress and its application for the diabetes control.

KLF regulation of insulin pathway genes

Alteration in lipid metabolism can result in fat accumulation in adipose tissues, which may lead to two most important human diseases, obesity and diabetes. A shift in lipid metabolism deregulates signaling pathways which regulates obesity and/or diabetes. In this study, we examined the components of insulin/ TGF-β pathways and their genetic interaction with Krüppel-like transcription factors (KLFs). Their role in energy homeostasis were discussed. We separately created klf/daf genes double mutants by carrying out klfs RNAi on daf-2 (e1391), daf-4 (e1364), daf-7 (e1372); dpy-1 (e1), daf-14 (m77), daf-16 (mgDf50) mutants. And then conducted Oil O Red staining to assay the klf/daf RNAi worms for fat deposits and examine genetic interaction between klfs and daf genes. The results showed that worms bearing klf-1, 2, or 3 and daf-2, or daf-4 mutations deposit large, but similar fat levels as individual mutants. The results suggested that they target the same molecular pathway of fat storage. klf-1, 2 or 3 RNAi /daf-7 worms showed higher fat deposits in klf-1, 2, or 3 RNAi/daf-7 worms than klf-1, 2, or 3 RNAi or daf-7 mutants alone, which showed a functional interaction between klfs and daf-7 in perhaps TGF-β-like pathway. Altogether our study suggests a direct role of klfs in insulin signaling pathway.

Large-Scale Operational Pyriproxyfen Autodissemination Deployment to Suppress the Immature Asian Tiger Mosquito (Diptera: Culicidae) Populations

Effective suppression of container-inhabiting Asian Tiger [Aedes albopictus (Skuse)] (Diptera: Culicidae) and yellow fever [Aedes aegypti (L.)] (Diptera: Culicidae) mosquitoes presents one of the most intractable problems for modern mosquito control. Traditional tools often fail to control populations of these mosquito species, and are prohibitively expensive or have negative environmental impacts. Novel approaches and tools are urgently needed for integrated container-inhabiting mosquito management programs. One of the most promising techniques is autodissemination. We present the results of a long-term large-scale study conducted in a temperate urbanized environment representing typical Ae. albopictus habitats. Three treatment sites with autodissemination stations and three nearby reference sites were monitored for eggs, immature, and adult mosquitoes over a period of 3 yr from 2014 to 2016. Elevated larval and pupal mortality of 12-19% on average was the most notable outcome in sentinel cups of the treatment sites. The number of eggs in the treatment sites was significantly reduced in 2014, but not in 2015 or 2016. Adult populations remained similar in treatment and reference sites throughout the study. The impact of autodissemination on mosquito populations was lower than reported by previous investigations. Technical and logistical problems associated with wider coverage and working in multiple urban neighborhoods contributed to reduced efficacy. Incorporating autodissemination with routine mosquito control operations and commercializing this methodology for general public use will require further research on combining this tool with other novel or conventional technologies.

Heterodissemination: precision targeting container Aedes mosquitoes with a cohabiting midge species carrying insect growth regulator

BACKGROUND

Management of Aedes albopictus and Ae. aegypti is challenging in large part due to the cryptic nature of their larval habitats. Autodissemination, using conspecific species to transfer pesticide, is unable to provide proactive control. Here we report results from a new hypothesis, heterodissemination, wherein females of the cohabiting non-biting midge, Chironomus decorus, reared in the laboratory, treated with pyriproxyfen, and released to transfer lethal concentrations to shared mosquito larval habitats.

RESULTS

Pyriproxyfen-impregnated oil and powder formulations were developed. The average payload for each female midge treated with oil followed by powder formulations was 5.07 ± 0.92 μg of active ingredient or 1660 times the median lethal concentration (LC₅₀ ) for Ae. albopictus or Ae. aegypti in 200 mL of water. Subsequent residue analysis showed pyriproxyfen transference from chironomids, treated with oil formulation only, into water-holding containers up to 2.06 ppb or 171.7 times the LC₅₀ . Releasing 20 laboratory reared and contaminated Chironomus decorus into a small room resulted in 80.42 ± 0.67% and 75.67 ± 3.14% Ae. albopictus pupal mortality in open and cryptic sentinel ovicups, respectively. Container water volumes ranging up to 4 L did not affect efficacy. In a large field cage, 90.3 ± 2.5% Ae. albopictus mortality was resulted from releasing 100 treated female midges. Releasing 400 contaminated midges into a residential backyard resulted in 74.3% pupal mortality in sentinel ovicups.

CONCLUSIONS

Room, large field cage and field release trials demonstrated that adult midges reared and treated in the laboratory transfer highly lethal concentrations of pyriproxyfen to Ae. albopictus container habitats. Heterodissemination provides a potential approach for precision, proactive mosquito control, which may draw attention for further studies. © 2020 Society of Chemical Industry.

Behavior manipulation of mosquitoes by a mermithid nematode

We examined manipulation of mosquito behavior by the parasitic mermithid nematode, Strelkovimermis spiculatus. This nematode species typically infects early instar host larvae and emerges after parasitic development to kill last-instar larvae. Parasitized adults, however, have occasionally been reported from field collections. We obtained low rates (1.7-11.5%) of parasitized adults in laboratory exposures only when Culex pipiens pipiens fourth-instar larvae nearing pupation were exposed to infective nematodes. This did not allow an adequate interval for parasitic development in immature host stages. Parasitized adult females in a multiple-choice assay were three times more likely to seek water than a blood source (63.1 vs. 20.5%), whereas uninfected females were twice as likely to seek blood than water (64%3.9 vs. 32.6%). This altered host behavior benefits the parasite by providing the only mechanism for dispersal and colonization of new host habitats while concurrently avoiding risks from the defensive behaviors associated with blood-feeding. Behavioral alternation in Cx. p. pipiens larval hosts was also examined using larvae infected as second instars to allow for a normal duration of parasitic development. As larvae neared pupation and parasite emergence, parasitized larvae became more spatially aggregated than unparasitized larvae. This altered host behavior benefits the parasite by providing a corresponding increase in post-parasite aggregation, which facilitates formation of large mating clusters and concomitantly reproductive success. Parasites derive fitness gains by overriding host autonomy, whereas hosts have zero fitness once parasitism is established, suggesting a coevolutionary response is inoperative and that the behavioral modifications may be adaptive.

Timing of Lambda-Cyhalothrin and Pyriproxyfen Barrier Treatments for Aedes albopictus (Diptera: Culicidae) Management

Barrier applications, treating vegetation and other potential mosquito resting areas with residual pesticides, have become standard practice for commercial pest management professionals offering mosquito control services. These treatments are generally effective in reducing numbers of the Asian tiger mosquito, Aedes albopictus (Skuse). In the temperate climates, adult Ae. albopictus populations are naturally eliminated each winter and must be grown from diapausing eggs the following spring. Therefore, early-season control interventions timed before populations rebound may further reduce population growth compared with interventions that take place after the population has peaked. We compared Early (1 June) barrier applications of lambda-cyhalothrin (Demand CS) mixed with the insect growth regulator pyriproxyfen (Archer IGR) to Late applications (31 July) in urban and suburban residential parcels in New Jersey. These applications resulted in 43 and 51% reductions in adult Ae. albopictus populations in the Early and Late intervention study parcels, respectively, when compared with the untreated Controls. Indirect applications of pyriproxyfen (i.e., rainwater runoff transferring pesticide) to potential larval habitat did not cause mortality in laboratory larval bioassays but direct mist applications of the Archer and Demand combination to larval habitats led to elevated larval mortality over a 6-wk period. The Early-season intervention offered no advantage in efficacy on adult populations compared with the Late-season intervention, which targeted peak mosquito populations. Our study provides support for the efficacy of barrier applications and illustrates the importance of timing barrier treatments to coincide with established Ae. albopictus action thresholds.

Truck-mounted area-wide applications of larvicides and adulticides for extended suppression of adult Aedes albopictus

BACKGROUND

Given the lack of vaccines for most vector-borne diseases, vector control is often the primary option for disease control. Aedes albopictus are difficult to control because the immatures primarily develop in containers ubiquitous in residential properties. Conventional adulticide campaigns often result in brief, rebounding population declines, so incorporating new techniques into an integrated pest management program is imperative. We performed combined area-wide applications of the larvicides Bacillus thuringiensis var. israelensis and pyriproxyfen with the adulticide sumithrin and prallethrin to achieve extended suppression of Ae. albopictus populations in Trenton, NJ, USA. We deployed bioassay cups to assess the spatial penetration and efficacy of the applications.

RESULTS

Inhibition of adult emergence was significantly higher in the treatment bioassay cups than in laboratory controls (z = 4.65, P < 0.0001) and field control bioassay cups (z = 8.93, P < 0.0001). We observed a lower trend in adult numbers following season-long combined application of pyriproxyfen and adulticide, with numbers of adult Ae. albopictus at the treatment site up to five times lower than at the control site.

CONCLUSION

Pyriproxyfen is a powerful mosquito larvicide and pupacide with low mammalian toxicity that shows promise for area-wide vehicle-mounted (either ground or airborne) applications. © 2018 Society of Chemical Industry.

Salts and energy balance: A special role for dietary salts in metabolic syndrome

BACKGROUND

Dietary salts sodium (Na⁺), potassium (K⁺), magnesium (Mg2⁺), and calcium (Ca2⁺) are important in metabolic diseases. Yet, we do not have sufficient understanding on the salts global molecular network in these diseases. In this systematic review we have pooled information to identify the general effect of salts on obesity, insulin resistance and hypertension.

AIMS

To assess the roles of salts in metabolic disorders by focusing on their individual effect and the network effect among these salts.

METHODS

We searched articles in PubMed, EMBASE and Google Scholar. We selected original laboratory research, systematic reviews, clinical trials, observational studies and epidemiological data that focused on dietary salts and followed the preferred reporting items for systematic review in designing the present systematic review.

RESULTS

From the initial search of 2898 studies we selected a total of 199 articles that met our inclusion criteria and data extraction. Alterations in metabolic pathways associated with the sensitivity of sodium, potassium, magnesium and calcium may lead to obesity, hypertension, and insulin resistance. We found that the results of most laboratory research, animal studies and clinical trials are coherent but some research outcome are either inconsistent or inconclusive.

CONCLUSION

Important of salts in metabolic disorder is evident. In order to assess the effects of dietary salts in metablic diseases, environmental factors, dietary habits, physical activity, and the microbiome, should be considered in any study. Although interest in this area of research continues to grow, the challenge is to integrate the action of these salts in metabolic syndrom.

Seasonal field efficacy of pyriproxyfen autodissemination stations against container-inhabiting mosquito Aedes albopictus under different habitat conditions

BACKGROUND

Control of the container-inhabiting mosquito, Aedes albopictus, is difficult using conventional methods due to its selection of cryptic peri-domestic habitats. We evaluated whether autodissemination stations can deliver sufficient pyriproxyfen to sentinel containers to produce significant pupal mortality in different habitats such as competing oviposition sites, peri-domestic habitats, junkyards and tire piles. We also tested how far the pesticide could be transferred over a 200-m range.

RESULTS

Autodissemination stations performed effectively for 8-12 weeks under field conditions. Pupal mortality was reduced in sentinel cups with high-competing oviposition habitats (5 versus 20) in isolated plots; however, similar results were not seen in residential areas. Increasing the number of stations per plot (from 1 to 4) enhanced the efficacy. Peri-domestic habitat trials showed the highest pupal mortality (50.4%) and site contamination with pyriproxyfen (82.2%) among the trials. Autodissemination stations were able to contaminate habitats in a junkyard (50.0%) and tire piles (40.2%). Pyriproxyfen was detected in sentinel cups up to 200 m from stations. Detection of pyriproxyfen by residue analysis (0.005-0.741 µg L^-1 ) in field samples confirmed the transfer of the insect growth regulator.

CONCLUSION

Autodissemination stations have shown promising potential as a novel pest management tool against container mosquitoes in field trials in different habitats confronted by mosquito control personnel. © 2017 Society of Chemical Industry.

Evaluation of Lambda-Cyhalothrin and Pyriproxyfen Barrier Treatments for Aedes albopictus (Diptera: Culicidae) Management in Urbanized Areas of New Jersey

Mosquito control programs in the United States are still searching for best management practices to control the Asian tiger mosquito, Aedes albopictus (Skuse; Diptera: Culicidae). Most intervention methods for this species are either labor intensive (e.g., source reduction) or short-term (e.g., ultra-low-volume adulticiding). We investigated the effectiveness of barrier spray pesticide applications within urban and suburban residential yards in New Jersey as a control strategy using a before-after-control-impact (BACI) approach. Applications of Demand CSR pyrethroid (9.7% AI lambda-cyhalothrin) only or combined Demand CSR and Archer IGR insect growth regulator (1.3% AI pyriproxyfen) applications resulted in significant and similar decreases in adult mosquito abundance post-treatment ranging from 78 to 74% respectively, compared with the untreated control. Both insecticides exceeded the 70% reduction threshold considered as effective for Ae. albopictus control for 2 to 4 wk. However, applications of Archer IGR alone did not reduce adult mosquito abundance. The field study results were supported by laboratory no-choice bioassays using treated leaf foliage. Our study is the first data driven evidence of the residual efficacy of barrier pesticide applications in New Jersey with lambda-cyhalothrin that provided significant reductions in adult Ae. albopictus populations for an extended duration.

Superparasitism and Population Regulation of the Mosquito-Parasitic Mermithid Nematodes Romanomermis iyengari and Strelkovimermis spiculatus

Superparasitism is a common phenomenon in mosquito-parasitic mermithid nematodes. Multiple nematodes are needed in a single host to produce males. Host selection behavior and intraspecific competition among Romanomermis iyengari and Strelkovimermis spiculatus were investigated against their host, Culex pipiens pipiens in laboratory experiments. In a choice assay between previously infected and uninfected host larvae, infectious preparasites of both nematode species could distinguish not only between infected and uninfected hosts, but even between different parasite loads in showing a strong preference for uninfected hosts or hosts with a low parasite load. Host heart rate declined briefly immediately after parasitism. Superparasitism resulted in increased parasite mortality. Scramble competition within mosquito larvae for limited host nutrients, coupled with a skewed sex ratio favoring males, is assumed to lead to parasite population decline and subsequently toward host-parasite population equilibrium. The ability of mermithid preparasites to accurately assess parasite load likely plays an important role in host population dynamics and regulation.

The role of copulatory plugs in the mosquito-parasitic nematode Strelkovimermis spiculatus

The mosquito-parasitic nematode, Strelkovimermis spiculatus (Mermithidae: Nematoda) emerges from hosts and aggregates to form mating clusters characterized by intense male-male competition for females. Successful males deposit an adhesive copulatory plug over the female vulva after insemination. In choice experiments, males strongly preferred virgin females, whereas plugged females were ignored. Males made no attempt to displace copulatory plugs deposited by previous males. Plugged females repelled males without the need for physical contact. The observed chemical repellency was independent of females, since excised plugs alone showed the same negative male response. Removal of the plug shortly after mating reduced fecundity by 90%, presumably due to spermatids leaking from the vulva. The plug as a nutritional gift hypothesis was rejected because there was no post-mating reduction in plug size that would have indicated absorption. Despite being a male adaption to sperm competition, we conclude that the copulatory plug serves the fitness needs of both males and females in multiple roles that include paternity preservation, reduced male harassment, improved male search for mates, increased fecundity, and sperm retention.

Effectiveness of autodissemination stations containing pyriproxyfen in reducing immature Aedes albopictus populations

Background

Aedes albopictus, the Asian tiger mosquito, is an aggressive, highly anthropophilic, day-biting mosquito with an expanding geographic range. Suppression of Ae. albopictus is difficult because of the abundance and prevalence of larval habitats within peridomestic environments, particularly cryptic habitats such as corrugated extension spouts, fence post openings, discarded food containers, etc. Because of the challenges of eliminating or treating larval habitats of this species, we tested an autodissemination concept to contaminate these habitats with the insect growth regulator pyriproxyfen.

Methods

Our study was conducted in the City of Trenton (Mercer County), New Jersey, USA (40°12′N, 74°44′W). We selected six hot spots, where five or more Ae. albopictus males or females were collected based on weekly trap surveillance. A trapping unit was a city block, approximately 0.8 ha (hot spot), where we deployed 26 to 28 autodissemination stations per treatment plot. To gauge efficacy, we deployed BGS traps, oviposition cups, and sentinel cups in treatment and control locations.

Results

We found a significant reduction in eggs (P < 0.0001) and larval populations (P < 0.0001) as a result of treatment. Pupal mortality, as determined through bioassays, was also significantly higher in the treatment sites (P < 0.0001).

Conclusion

Our results clearly show the potential and unique use of the autodissemination stations to control immature Ae. albopictus in urban areas. Penetration of larvicides with existing methods are difficult to reach cryptic habitats, but the autodissemination approach, which exploits the oviposition behavior of the target pest, can be integrated into intervention programs. New tools are urgently needed to curb the expansion and public health implications of Ae. albopictus and other container-inhabiting species.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2034-7) contains supplementary material, which is available to authorized users.

Defective lipid metabolism associated with mutation in klf-2 and klf-3: important roles of essential dietary salts in fat storage

Background

Dietary salts are important factors in metabolic disorders. They are vital components of enzymes, vitamins, hormones, and signal transduction that act synergistically to regulate lipid metabolism. Our previous studies have identified that Krüppel-like factor −3 (KLF-3) is an essential regulator of lipid metabolism. However, it is not known if KLF-2 also regulates lipid metabolism and whether KLF-2 and −3 mediate the effects of dietary salts on lipid metabolism.

Methods

In this study, we used klf mutants [homozygous klf-2 (ok1043) V and klf-3 (ok1975) II mutants] to investigate the role of dietary salts in lipid metabolism. All gene expression was quantified by qRT-PCR. Localization of KLF-2 was analyzed by the expression of klf-2::gfp (in pPD95.75 vector) using a fluorescent microscope. Fat storage was measured by Oil Red O staining.

Results

Klf-2 was identified to express in the intestine during all stages of Caenorhabditis elegans development with peak expression at L3 stage. Mutation of klf-2 increased fat accumulation. Under regular growth media free of Ca^2+, the expression of both klf-2 and −3 was inhibited slightly; further their expression reduced significantly in WT worms fed on 10X Ca²⁺ diet. When klf-3 was mutated, the expression of klf-2 increased under 10X Ca²⁺ diet; but when klf-2 was mutated, the expression of klf-3 was not altered under 10X Ca²⁺ diet. Overall, Mg²⁺ and K⁺ were less effective on the gene expression of klfs. KLF target gene Ce-C/EBP-2 showed elevated expression in WT and klf-3 (ok1975) worms with changed Ca²⁺ concentrations but not in klf-2 (ok1043) worms. However, high Ca⁺² diet exhibited inhibitory effect on Ce-SREBP expression in WT worms.

Conclusion

Dietary Ca²⁺ is most effective on fat storage and klf-2 expression, wherein high Ca²⁺ diet decreased klf-2 expression and reduced fat buildup. Mechanistic study identified Ce-C/EBP (C48E7.3; lpd-2) and Ce-SREBP (Y47D3B.7; lpd-1) as the target genes of klf-2 and/or klf-3 to mediate lipid metabolism. This study identifies a new function of klf-2 in inhibiting fat buildup and reveals the interplay between dietary salts and klf-2 and klf-3 in lipid metabolism.

Droplet Characterization and Penetration of an Ultra-Low Volume Mosquito Adulticide Spray Targeting the Asian Tiger Mosquito, Aedes albopictus, within Urban and Suburban Environments of Northeastern USA

Adult control of Aedes albopictus via ultra-low volume is difficult because this species occurs primarily in peridomestic habitats where obstacles such as buildings and vegetation can disrupt spray plumes and droplet dispersion. We determined droplet penetration and characterization of a pyrethroid adulticide applied from the ground at mid (46.77 ml/ha) and maximum (93.53 ml/ha) label rates within cryptic habitats of urban and suburban environments. Droplets were collected from all habitats, with no significant differences detected between locations within the same application rate or collection method. No differences were detected in droplet densities (drops per mm²) between rates within urban environments, but more droplets were collected in urban (149.93 ± 11.07 SE) than suburban sites (114.37 ± 11.32) at the maximum label rate (P = 0.003). The excellent penetration of aerosols into cryptic habitats of an urban site was likely due to the shorter spray paths afforded by our network of roads and alleys. Mid label rates displayed similar droplet density values as maximum label rates in urban areas, indicating that lower rates may be used effectively to reduce costs, lessen non-target effects, and increase environmental stewardship. Advances in formulations and technology are driving changes in adulticide applications, leading to use of the minimum effective dose for maximum efficacy, precision, and accountability.

Experimental host preference of diapause and non-diapause induced Culex pipiens pipiens (Diptera: Culicidae)

BACKGROUND

Culex pipiens pipiens plays an important role in the transmission of several vector-borne pathogens such as West Nile virus (WNV) in North America. Laboratory and field studies suggest that this species is ornithophilic but because of genetic hybridization with sibling species during the active mosquito season, it may occasionally feed on mammals. Adult female Cx. p. pipiens undergo a facultative diapause and may serve as an overwintering mechanism for WNV. To determine the effect of diapause on the innate host preference of Cx. p. pipiens emerging from winter hibernation, we conducted host-choice experiments using bird and mammal hosts.

METHODS

Mosquitoes were reared under non-diapause induced (NDI), diapause induced (DI), and field collected from overwintering (OW) hibernaculae. They were released into a large mesh enclosure housing two lard can traps, and given a choice between feeding on a dove or a rat.

RESULTS

Host seeking Cx. p. pipiens were four times more likely to feed on the dove than the rat, regardless of experimental conditions. Under NDI conditions, Cx. p. pipiens were (p < 0.001) more attracted to the bird (79.9% [75.6-84.1]) than the rat (20.1 [15.9-24.4]). Overwintering mosquitoes and those exposed to DI conditions were also significantly (p < 0.001) more attracted to birds (81.6% [75.9-87.3]) than to rats (18.5 [12.7-24.2]).

CONCLUSIONS

We provide new information about the innate host preference of Cx. p. pipiens emerging from diapause in temperate habitats where winter survival is crucial for disease transmission cycles. Although we showed that Cx. p. pipiens prefers an avian to a mammalian host, nearly 20% of emerging mosquitoes in the spring could feed on mammals. Changes in host preferences may also contain valuable clues about transmission dynamics and subsequent timely interventions by vector control and public health practitioners.

The Insect Growth Regulator Pyriproxyfen Terminates Egg Diapause in the Asian Tiger Mosquito, Aedes albopictus

The Asian tiger mosquito, Aedes albopictus, is a highly invasive mosquito species that transmits chikungunya and dengue. This species overwinters as diapausing eggs in temperate climates. Early diapause termination may be a beneficial strategy for winter mosquito control; however, a mechanism to terminate the diapause process using chemicals is not known. We tested the hypothesis that a hormonal imbalance caused by the administration of juvenile hormone analog would terminate egg diapause in A. albopictus. We tested the insect growth regulator pyriproxyfen on all developmental stages to identify a susceptible stage for diapause termination. We found that pyriproxyfen treatment of mosquito eggs terminated embryonic diapause. The highest rates of diapause termination were recorded in newly deposited (78.9%) and fully embryonated (74.7%) eggs at 0.1 and 1 ppm, respectively. Hatching was completed earlier in newly deposited eggs (25-30 days) compared to fully embryonated eggs (71-80 days). The combined mortality from premature diapause termination and ovicidal activity was 98.2% in newly deposited and >98.9% in fully embryonated eggs at 1 ppm. The control diapause eggs did not hatch under diapausing conditions. Pyriproxyfen exposure to larvae, pupae and adults did not prevent the females from ovipositing diapausing eggs. There was no effect of pyriproxyfen on diapausing egg embryonic developmental time. We also observed mortality in diapausing eggs laid by females exposed to pyriproxyfen immediately after blood feeding. There was no mortality in eggs laid by females that survived larval and pupal exposures. In conclusion, diapausing eggs were the more susceptible to pyriproxyfen diapause termination compared to other life stages. This is the first report of diapause termination in A. albopictus with a juvenile hormone analog. We believe our findings will be useful in developing a new control strategy against overwintering mosquito populations.

Long-term Effects of Carbohydrate Availability on Mating Success of Newly Eclosed Aedes albopictus (Diptera: Culicidae) Males

Sugar availability varies greatly in nature, and determining how this affects male mosquito fitness is essential for understanding population dynamics. We allowed male Aedes albopictus (Skuse) carbohydrate access for increasing intervals of time immediately after eclosion and we evaluated their fitness by comparing mortality, mating success, and sperm transfer. We compared individual male Ae. albopictus, which were offered water or 20% sucrose solution for 24, 48, or 72 h. As predicted, there were significant increases in fitness for each additional day of sucrose access. Following sugar exposure, we allowed males daily access to three virgin females. We assessed mating success through observation of spermatozoa in the female spermathecae. When individuals of the same age were compared, males with sugar access exhibited significantly greater mating success than water-treated males in all treatments. The total number of spermathecae filled by males with sugar access in the 48- and 72-h treatments was also significantly greater on some days; these were 3-5 d posteclosion in the 48-h treatment and 5-6 d posteclosion in the 72-h treatment. We conclude that extended sugar access at eclosion is important for maximizing fitness in male Ae. albopictus and should be applicable to sterile male release efforts, especially when laboratory-reared males suffered from other disadvantages. We recommend retaining adult males for 3 d posteclosion prior to release to improve their mating success in male release initiatives.

Economic evaluation of an area-wide integrated pest management program to control the Asian tiger mosquito in New Jersey

Aedes albopictus is the most invasive mosquito in the world, an important disease vector, and a biting nuisance that limits outdoor activities. Area-wide integrated pest management (AW-IPM) is the recommended control strategy. We conducted an economic evaluation of the AW-IPM project in Mercer and Monmouth Counties, New Jersey with a controlled design (AW-IPM vs. control) from 2009 through 2011. The study analyzed financial documents and staff time for AW-IPM and surveyed an average of 415 randomly chosen households in AW-IPM and control areas each fall from 2008 through 2011. Hours lost from yard and porch activities were calculated as differences between actual and potential hours of these activities in an average summer week if there had been no mosquito concerns. Net estimated benefits of AW-IPM were based on cross-over and difference-in-difference analyses. Reductions in hours lost were valued based on respondents' willingness to pay for a hypothetical extra hour free of mosquitoes spent on yard or porch activities and literature on valuation of a quality adjusted life year (QALY). The incremental cost of AW-IPM per adult was $41.18 per year. Number of hours lost due to mosquitoes in AW-IPM areas between the base year (2008) and the intervention years (2009-2011) declined by 3.30 hours per summer week in AW-IPM areas compared to control areas. Survey respondents valued this improvement at $27.37 per adult per summer week. Over the 13-week summer, an average adult resident gained 42.96 hours of yard and porch time, worth $355.82. The net benefit over the summer was $314.63. With an average of 0.0027 QALYs gained per adult per year, AW-IPM was cost effective at $15,300 per QALY gained. The benefit-cost ratio from hours gained was 8.64, indicating that each $1 spent on AW-IPM gave adults additional porch and yard time worth over $8.

Area-wide ground applications of Bacillus thuringiensis var. israelensis for the control of Aedes albopictus in residential neighborhoods: from optimization to operation

The increasing range of Aedes albopictus, the Asian tiger mosquito, in the USA and the threat of chikungunya and dengue outbreaks vectored by this species have necessitated novel approaches to control this peridomestic mosquito. Conventional methods such as adulticiding provide temporary relief, but fail to manage this pest on a sustained basis. We explored the use of cold aerosol foggers and misting machines for area-wide applications of Bacillus thuringiensis var. israelensis (VectoBac WDG) as a larvicide targeting Aedes albopictus. During 2010–2013 we performed initially open field trials and then 19 operational area-wide applications in urban and suburban residential areas in northeastern USA to test three truck-mounted sprayers at two application rates. Area-wide applications of WDG in open field conditions at 400 and 800 g/ha killed on average 87% of tested larvae. Once techniques were optimized in residential areas, applications with a Buffalo Turbine Mist Sprayer at a rate of 800 g/ha, the best combination, consistently provided over 90% mortality. Importantly, there was no significant decrease in efficacy with distance from the spray line even in blocks of row homes with trees and bushes in the backyards. Under laboratory conditions Bti deposition in bioassay cups during the operational trials resulted in over 6 weeks of residual control. Our results demonstrate that area-wide truck mounted applications of WDG can effectively suppress Ae. albopictus larvae and should be used in integrated mosquito management approaches to control this nuisance pest and disease vector.

Vertical Oviposition Preferences of the Asian Tiger Mosquito, Aedes albopictus, In Temperate North America

As a hyperaggressive mosquito that is also a public health threat, Aedes albopictus (Skuse), the Asian tiger mosquito, is a major priority for control efforts. We examine one aspect of Ae. albopictus biology: oviposition height. Field-based research in an urban habitat was conducted to determine if a height preference exists for this species. Larval and egg counts showed a significant preference for oviposition at ground level (0 m) compared to heights of 1, 2, 3, or 4 m (P < 0.01). An experiment conducted under semi-field conditions supported our conclusion of oviposition preference at ground level (P < 0.001), and further defines the search image needed by mosquito control personnel when dealing with this invasive species.

Differences in male-female ratios of Aedes albopictus (Diptera: Culicidae) following ultra-low volume adulticide applications

Suppression of Aedes albopictus populations is a substantial challenge for mosquito control programs globally because juveniles of this species are found in numerous kinds of domestic artificial containers that are difficult to detect, access, and eliminate. We conducted a multi-year assessment of the effect of different interventions to control Ae. albopictus near the northernmost geographic boundary of the species in temperate North America and deployed an array of BG-Sentinel traps for adult surveillance. Here we present the results of a comparative examination of adult sex ratios in urban and suburban areas, shifts in sex ratios after control interventions, and a discussion of the critical drivers of population dynamics of Ae. albopictus in our area. We collected significantly more male mosquitoes in urban as compared to suburban areas in June through September, but not in May (p<0.001). The higher number of male mosquitoes in urban areas could be attributed to a higher number of larval habitats within a closer proximity of the surveillance traps and the lower flight dispersal of males. Following application of adulticides in urban areas, Ae. albopictus male populations were reduced by 88% on average, which was higher than the 69% reduction in female populations. The higher reduction of male mosquitoes could be attributed to the smaller body mass of the males and their higher susceptibility to adulticides. The results of this study are directly relevant to the development of suitable control strategies that depend on manipulation of males, such as the sterile insect technique. The results could also be used to refine mosquito abatement by providing more accurate methods to determine the need and timing of vector control.

Comparative host feeding patterns of the Asian tiger mosquito, Aedes albopictus, in urban and suburban Northeastern USA and implications for disease transmission

Background

Aedes albopictus is an invasive species which continues expanding its geographic range and involvement in mosquito-borne diseases such as chikungunya and dengue. Host selection patterns by invasive mosquitoes are critically important because they increase endemic disease transmission and drive outbreaks of exotic pathogens. Traditionally, Ae. albopictus has been characterized as an opportunistic feeder, primarily feeding on mammalian hosts but occasionally acquiring blood from avian sources as well. However, limited information is available on their feeding patterns in temperate regions of their expanded range. Because of the increasing expansion and abundance of Ae. albopictus and the escalating diagnoses of exotic pathogens in travelers returning from endemic areas, we investigated the host feeding patterns of this species in newly invaded areas to further shed light on its role in disease ecology and assess the public health threat of an exotic arbovirus outbreak.

Methodology/Principal Findings

We identified the vertebrate source of 165 blood meals in Ae. albopictus collected between 2008 and 2011 from urban and suburban areas in northeastern USA. We used a network of Biogents Sentinel traps, which enhance Ae. albopictus capture counts, to conduct our collections of blooded mosquitoes. We also analyzed blooded Culex mosquitoes collected alongside Ae. albopictus in order to examine the composition of the community of blood sources. We found no evidence of bias since as expected Culex blood meals were predominantly from birds (n = 149, 93.7%) with only a small proportion feeding on mammals (n = 10, 6.3%). In contrast, Aedes albopictus fed exclusively on mammalian hosts with over 90% of their blood meals derived from humans (n = 96, 58.2%) and domesticated pets (n = 38, 23.0% cats; and n = 24, 14.6% dogs). Aedes albopictus fed from humans significantly more often in suburban than in urban areas (χ², p = 0.004) and cat-derived blood meals were greater in urban habitats (χ², p = 0.022). Avian-derived blood meals were not detected in any of the Ae. albopictus tested.

Conclusions/Significance

The high mammalian affinity of Ae. albopictus suggests that this species will be an efficient vector of mammal- and human-driven zoonoses such as La Crosse, dengue, and chikungunya viruses. The lack of blood meals obtained from birds by Ae. albopictus suggest that this species may have limited exposure to endemic avian zoonoses such as St. Louis encephalitis and West Nile virus, which already circulate in the USA. However, growing populations of Ae. albopictus in major metropolitan urban and suburban centers, make a large autochthonous outbreak of an arbovirus such as chikungunya or dengue viruses a clear and present danger. Given the difficulties of Ae. albopictus suppression, we recommend that public health practitioners and policy makers install proactive measures for the imminent mitigation of an exotic pathogen outbreak.

Aedes albopictus is one of the most invasive and aggressive disease vectors in the world. The range of this species is currently still expanding, particularly into highly dense human population centers in temperate areas in the USA and Europe, raising the public health threat of emerging and re-emerging diseases such as chikungunya and dengue. The prominence of Ae. albopictus as a major vector was exposed during the global pandemic of chikungunya virus, primarily because of a virus adaptation which enhanced the transmission efficiency by this mosquito species and also because of the first locally-transmitted cases of chikungunya virus in temperate Europe. Blood feeding patterns by mosquitoes are a critical component of virus proliferation and determine the degree and intensity of disease epidemics, particularly in newly invaded areas. We examined the blood meal sources of invasive Ae. albopictus in the northernmost boundary of their range in temperate North America and found that the species fed exclusively on mammalian hosts, with over 90% of their blood meals derived from humans and their associated pets (cats and dogs). The high mammalian affinity of Ae. albopictus suggests that this species may be an efficient vector of mammal-driven zoonoses and human-driven anthroponoses such as dengue and chikungunya viruses in this region.

Dual-treatment autodissemination station with enhanced transfer of an insect growth regulator to mosquito oviposition sites

BACKGROUND

The Asian tiger mosquito, Aedes albopictus (Skuse), transmits important arboviral diseases and displaces native species. This peridomestic mosquito deposits eggs in natural and artificial containers. Container larval habitats tend to be cryptic and, therefore, difficult to reach by conventional insecticide treatments. We have developed an autodissemination station that transfers the insect growth regulator, pyriproxyfen, from the station to oviposition sites. Mosquitoes visiting the station become contaminated with an oil sticker followed by pyriproxyfen powder before exiting.

RESULTS

In a room (31 m(3) ) bioassay a single station consistently achieved 100% Ae. albopictus pupal mortality against 10 oviposition containers. In a greenhouse (200 m(3) ) assay with two stations and 12 oviposition cups, 91.7% of the cups had been contaminated as shown, and 57.1% pupal mortality was recorded. Pyriproxyfen transfer was also detected by visualizing mosquito 'tarsal prints' using a fluorescent dye.

CONCLUSIONS

The oil and pyriproxyfen powder dual-treatment station enhanced autodissemination efficacy by increasing toxicant attachment and retention on contaminated females. The autodissemination station offers a targeted, less environmentally damaging approach to manage cryptic container species.

Point-source and area-wide field studies of pyriproxyfen autodissemination against urban container-inhabiting mosquitoes

Autodissemination of insecticides is a novel strategy for mosquito management. We tested if contaminated Aedes albopictus (Skuse) mosquitoes from a small area treated with commercial formulations (79gm a.i. pyriproxyfen/ha) using conventional techniques, would disseminate pyriproxyfen over a wider area. Pyriproxyfen showed LC50=0.012 ppb for Ae. albopictus. Direct treatment and autodissemination efficacy was measured as a pupal mortality by conducting Ae. albopictus larval bioassay. A tire pile (n=100 tires) treated by backpack sprayer as a point-source treatment showed higher pupal mortality in 2010 (60.8% for week 0-6) than in 2011 (38.3% for week 0-6). The sentinel containers placed for autodissemination in four compass directions out to 200-400m from the tire pile showed 15.8% pupal mortality (week 1-6) in the first year, and 1.4% pupal mortality in the second year. No significant difference was detected among the distances and direction for pupal mortality. In area-wide treatments, vegetation was sprayed in checkerboard pattern (3.7% of 105ha) using backpack sprayer in 2010 and in strips (24.8% of 94ha) using truck-mounted ultra-low volume (ULV) sprayer in 2011. In both years, the area-wide direct treatment efficacy was lower (30.3% during 2010 and 5.3% in 2011) than point-source treatments. Autodissemination in area-wide plots was higher in 2010 (10.3%) than 2011 (2.9%). However, area-wide treatments were ineffective on field populations of Ae. albopictus as monitored by using BGS traps. We found accumulation of pyriproxyfen in the week 6 autodissemination containers in both experiments. The differences in autodissemination in 2010 and 2011 can be attributed to higher rainfall in the second year that may have eroded the pyriproxyfen from treatment surfaces and sentinel containers. Our study shows that ULV surface treatments of conventional formulation do not work for autodissemination. The effectiveness of pyriproxyfen in autodissemination may be improved by developing specific formulations to treat vegetation and tires that can load high doses on mosquitoes.

Taming a tiger in the city: comparison of motorized backpack applications and source reduction against the Asian tiger mosquito, Aedes albopictus

We evaluated 2 strategies to manage Aedes albopictus: 1) motorized backpack applications and 2) source reduction (coupled with hand-applied applications of larvicide). Backpack applications used a water-dispersible granular formulation (VectoBac WDG) of Bacillus thuringiensis var. israelensis (Bti), whereas source reduction used granular formulations of the insect growth regulator methoprene (Altosid) combined with a monomolecular film surfactant (Agnique). Six subplots (total 8.02 ha) were selected for backpack applications, source reduction, and control groups. The experiments were blind with applications conducted randomly and independently. Efficacy was determined through placement of bioassay cups with larvae within experimental plots 1 day before treatment. Backpack applications resulted in 76% (+/- 8.2% SE) and source reduction resulted in 92% (+/- 4.1% SE) larval mortality. Backpack applications required 50 times less labor than source reduction (0.25 versus 0.005 ha/h). The cost of backpack applications, including labor, was $159.88/ha, compared with $659.65/ha for source reduction. Although overall efficacy was slightly lower, motorized backpack applications of Bti were more efficient and cost-effective than source reduction methods to control Ae. albopictus in urban settings at the community level.

Quantifying the impact of mosquitoes on quality of life and enjoyment of yard and porch activities in New Jersey

The recent expansion of Aedes albopictus, a day-biting mosquito, to densely inhabited areas in the northeastern Atlantic states of the USA has dramatically increased the problem that mosquitoes create for urban and suburban residents. We quantified the impact of mosquitoes on residents' quality of life within the context of a comprehensive area-wide integrated pest management program to control Ae. albopictus in two counties (Mercer and Monmouth) in New Jersey. We interviewed residents of 121 randomly selected households in both counties between October and November 2010. We asked residents about their experience with mosquitoes in their neighborhood and the importance of the ability to relax outdoors without mosquitoes compared to other neighborhood characteristics (1 = not important, 5 = extremely important). We rated residents' utility based on paired comparisons to known states from the EuroQol health description system. The majority (54.6%) of respondents considered mosquitoes to be a problem. Respondents reported an average of 7.1 mosquito bites in a typical week during that summer. Mosquitoes prevented 59.5% of residents from enjoying their outdoor activities at least to some extent. Residents rated the mosquito acceptability (mean ± standard deviation) during that summer on a scale of 0 (mosquito invasion) to 100 (no mosquitoes) at 56.7±28.7, and their overall utility at 0.87±0.03. This is comparable to living with up to two risk factors for diabetes (i.e., abdominal obesity, body mass index of 28 or more, reported cholesterol problems, diagnosis of hypertension, or history of cardiovascular disease) or women experiencing menstrual disorders. Respondents rated the importance of enjoying outdoor activities without mosquitoes (4.69±0.80) comparable to that of neighborhood safety (4.74±0.80) and higher than that of a clean neighborhood (4.59±0.94). In conclusion, New Jersey residents reported that mosquitoes decreased their utility by 0.13, comparable to the loss from worrisome health risk factors, underscoring the importance of controlling this problem.

Area-wide management of Aedes albopictus. Part 2: gauging the efficacy of traditional integrated pest control measures against urban container mosquitoes

BACKGROUND

Aedes (Stegomyia) albopictus (Skuse) is an important disease vector and biting nuisance. During the 2009 active season, six ∼1000-parcel sites were studied, three in urban and three in suburban areas of New Jersey, United States, to examine the efficacy of standard integrated urban mosquito control strategies applied area wide. Active source reduction, larviciding, adulticiding and public education (source reduction through education) were implemented in one site in each county, an education-only approach was developed in a second site and a third site was used as an untreated experimental control. Populations were surveyed weekly with BG-Sentinel traps and ovitraps.

RESULTS

A substantial reduction in Ae. albopictus populations was achieved in urban sites, but only modest reductions in suburban sites. Education alone achieved significant reductions in urban adult Ae. albopictus. Egg catches echoed adult catches only in suburban sites.

CONCLUSIONS

There are significant socioeconomic and climatic differences between urban and suburban sites that impact upon Ae. albopictus populations and the efficacy of the control methods tested. An integrated pest management approach can affect abundances, but labor-intensive, costly source reduction was not enough to maintain Ae. albopictus counts below a nuisance threshold. Nighttime adult population suppression using truck-mounted adulticides can be effective. Area-wide cost-effective strategies are necessary.

Assessment of a direct application of two Bacillus thuringiensis israelensis formulations for immediate and residual control of Aedes albopictus

The bacterial agent Bacillus thuringiensis israelensis (Bti) is a highly effective larvicide against various medically important mosquito and black fly vector species. Recent formulations of this powerful larvicidal tool have been evaluated for their field efficacy in integrated mosquito management programs. Laboratory and controlled-condition trials have indicated long periods of residual efficacy, whereas field persistence is often much lower in duration. We investigated the residual persistence of high doses of 2 formulations of Bti, a water-dispersible granule (VectoBac WDG; 16 mg/liter) and an extruded pellet (VBC-60066; 80 mg/liter), for the management of natural larval populations of Aedes albopictus. Laboratory tests demonstrated 100% (WDG) and > or = 99.7% (VBC) average mortality across all treatments over 180 days. Field tests exhibited 100% efficacy (WDG and VBC) for 3 wk against Ae. albopictus and other coinhabiting mosquito species, with some residual efficacy lasting for > 4 wk. These results are discussed in relation to current field control of domestic Aedes vectors of public health significance.

Host recognition by entomopathogenic nematodes: Behavioral response to contact with host feces

Host recognition by entomopathogenic nematodes may occur through contact with insects' excretory products, cuticle, or gut contents. We analyzed the behavioral responses of four species of entomopathogenic nematodes during contact with feces of natural or experimental hosts. Host recognition by nematodes was manifested in alterations in the frequency and/or duration of one or more search parameters including forward crawling, headwaving, body-waving, stopping, backward crawling, head-rubbing, and headthrusting.Heterorhabditis bacteriophora andSteinernema glaseri showed behavioral responses to contact with feces of their natural hosts,Spodoptera exigua (Lepidoptera) andPopillia japonica (Coleoptera), and to the experimental hosts,Acheata domesticus (Orthoptera) andBlatella germanica (Blatteria).Steinernema carpocapsae responded only toB. germanica feces, whereas5. scapterisci did not significantly respond to any of the insect species. During contact with cockroach feces, all nematodes, exceptS. scapterisci, showed avoidance behavior. We suggest that ammonia present in cockroach feces is inhibitory to nematodes. Specific host recognition by entomopathogenic nematodes may be an important mechanism to maintain host affinities.

Effects of larval habitat substrate on pyriproxyfen efficacy against Aedes albopictus (Diptera: Culicidae)

Pyriproxyfen, a juvenile hormone analog insect growth regulator (IGR), is a recommended insecticide for the control of container-inhabiting mosquitoes. The effects of eight container substrates (three plastics, wood, tire rubber, clay pot, concrete, and glass) were studied on reduction of bio-efficacy of pyriproxyfen for Aedes albopictus (Skuse) in the laboratory. Insect growth regulator-bioassay of third instars showed significant increase of LC50 with some substrates compared with control probably because of pyriproxyfen adsorption to the substrate. The LC50 for the control substrate (glass mug) was 0.029 microg/liter. In comparison to the control, LC50 increased 150.1 times with tire rubber (4.354 microg/liter) and 8-10 times with wood and high-density polyethylene plastic containers. Slight increases of LC50 were detected for clay pots, polypropylene, and polystyrene plastics (1.9-2.7 times). Pyriproxyfen efficacy with concrete substrate was higher than with glass containers, which might be caused by high pH. The pH of water with wood (5.6) and concrete (9.8) substrates differed from the other substrates tested (6.3-7.1). There was no pupal mortality at pH 5-11 without pyriproxyfen; however, interaction of pH (5-11) with pyriproxyfen (0.05 microg/liter) showed additive effects at both low and high pH values. Different substrates have variable impacts on pyriproxyfen efficacy, which might be associated with the failure of larval control strategies for the container mosquitoes under certain field conditions.

Isolations of Cache Valley virus from Aedes albopictus (Diptera: Culicidae) in New Jersey and evaluation of its role as a regional arbovirus vector

The Asian tiger mosquito, Aedes albopictus (Skuse), is an invasive species and a major pest problem in urban and suburban locales in New Jersey. To assess its potential role as an arbovirus vector, we sampled Ae. albopictus from two New Jersey counties over a 3-yr period and estimated the prevalence of virus infection by Vero cell culture and reverse transcription-polymerase chain reaction assays. Three virus isolates were obtained from 34,567 field-collected Ae. albopictus, and all were identified as Cache Valley virus by molecular methods. Ae. albopictus (N = 3,138), collected in Mercer County from late July through early September 2011, also were retested for West Nile virus (WNV) by reverse transcription-polymerase chain reaction, and all were negative. These results corroborate previous findings showing that Ae. albopictus may occasionally acquire Cache Valley virus, a deer-associated arbovirus, in nature. In contrast, we did not detect WNV infection in Ae. albopictus despite concurrent WNV amplification in this region.

Ovicidal activity of three insect growth regulators against Aedes and Culex mosquitoes

Interspecific variations in the susceptibility of freshly and embryonated eggs of Aedes albopictus, Ae. aegypti, Ae. atropalpus and Culex pipiens were tested against three classes of insect growth regulators (IGRs) including ecdysone agonist (azadirachtin), chitin synthesis inhibitor (diflubenzuron) and juvenile hormone analog (pyriproxyfen) at 0.001, 0.01, 0.1 and 1.0ppm concentrations. Egg hatching inhibition was dose dependent, the highest being at 1.0ppm concentration for freshly laid eggs of Ae. albopictus (pyriproxyfen: 80.6%, azadirachtin: 42.9% and diflubenzuron: 35.8%). Aedes aegypti showed lower egg hatching inhibition when exposed to pyriproxyfen (47.3%), azadirachtin (15.7%) and diflubenzuron (25.5%). Freshly laid eggs of Cx. pipiens were most susceptible to diflubenzuron. Aedes atropalpus eggs were tolerant to all three classes of IGRs. Embryonated eggs of Ae. albopictus, Ae. aegypti, Ae. atropalpus and Cx. pipiens were resistant to pyriproxyfen, azadirachtin and diflubenzuron than freshly laid eggs. The median desiccation time (DT50) of Ae. atropalpus eggs was maximum (5.1h) as compared to Ae. aegypti (4.9h), Ae. albopictus (3.9h) or Cx. pipiens (1.7h) eggs. Insignificant relationship between the rates of desiccation and egg hatching inhibition suggests other factors than physical providing eggs the ability to tolerate exposures to various IGRs. Egg hatching inhibition was due to the alteration in embryonic development caused by IGRs. Changes in the egg shell morphology and abnormal egg hatching from the side of the egg wall instead of operculum, was observed at higher concentrations of diflubenzuron. Morphological and physiological variations in eggs may be the key factor to influence the ovicidal efficacy of IGRs. The present data provide a base line for the improvement of the ovicidal efficacy of the insecticide and its formulation.

A lover and a fighter: the genome sequence of an entomopathogenic nematode Heterorhabditis bacteriophora

Heterorhabditis bacteriophora are entomopathogenic nematodes that have evolved a mutualism with Photorhabdus luminescens bacteria to function as highly virulent insect pathogens. The nematode provides a safe harbor for intestinal symbionts in soil and delivers the symbiotic bacteria into the insect blood. The symbiont provides virulence and toxins, metabolites essential for nematode reproduction, and antibiotic preservation of the insect cadaver. Approximately half of the 21,250 putative protein coding genes identified in the 77 Mbp high quality draft H. bacteriophora genome sequence were novel proteins of unknown function lacking homologs in Caenorhabditis elegans or any other sequenced organisms. Similarly, 317 of the 603 predicted secreted proteins are novel with unknown function in addition to 19 putative peptidases, 9 peptidase inhibitors and 7 C-type lectins that may function in interactions with insect hosts or bacterial symbionts. The 134 proteins contained mariner transposase domains, of which there are none in C. elegans, suggesting an invasion and expansion of mariner transposons in H. bacteriophora. Fewer Kyoto Encyclopedia of Genes and Genomes Orthologies in almost all metabolic categories were detected in the genome compared with 9 other sequenced nematode genomes, which may reflect dependence on the symbiont or insect host for these functions. The H. bacteriophora genome sequence will greatly facilitate genetics, genomics and evolutionary studies to gain fundamental knowledge of nematode parasitism and mutualism. It also elevates the utility of H. bacteriophora as a bridge species between vertebrate parasitic nematodes and the C. elegans model.

Regulation of lipoprotein assembly, secretion and fatty acid β-oxidation by Krüppel-like transcription factor, klf-3

Lipid metabolism is coordinately regulated through signaling networks that integrate biochemical pathways of fat assimilation, mobilization and utilization. Excessive diversion of fat for storage is a key risk factor for many fat-related human diseases. Dietary lipids are absorbed from the intestines and transported to various organs and tissues to provide energy and maintain lipid homeostasis. In humans, disparity between triglycerides (TG) synthesis and removal, via mitochondrial β-oxidation and VLDL (very low density lipoprotein) secretion, causes excessive TG accumulation in the liver. The mutation in Caenorhabditis elegans KLF-3 leads to high TG accumulation in the worm's intestine. Our previous data suggested that klf-3 regulates lipid metabolism by promoting fatty acid β-oxidation. Depletion of cholesterol in the diet has no effect on fat deposition in klf-3 (ok1975) mutants. Addition of vitamin D in the diet, however, increases fat levels in klf-3 worms. This suggests that excess vitamin D may be lowering the rate of fatty acid β-oxidation, with the eventual increase in fat accumulation. We also demonstrate that mutation in klf-3 reduces expression of C. elegans dsc-4 and/or vit genes, the orthologs of mammalian microsomal triglyceride transfer protein and apolipoprotein B, respectively. Both microsomal triglyceride transfer protein and apolipoprotein B are essential for mammalian lipoprotein assembly and transport, and mutation in both dsc-4 (qm182) and vit-5 (ok3239) results in high fat accumulation in worm intestine. Genetic interactions between klf-3 and dsc-4, as well as vit-5 genes, suggest that klf-3 may have an important role in regulating lipid assembly and secretion.

A C. elegans model to study human metabolic regulation

Lipid metabolic disorder is a critical risk factor for metabolic syndrome, triggering debilitating diseases like obesity and diabetes. Both obesity and diabetes are the epicenter of important medical issues, representing a major international public health threat. Accumulation of fat in adipose tissue, muscles and liver and/or the defects in their ability to metabolize fatty acids, results in insulin resistance. This triggers an early pathogenesis of type 2 diabetes (T2D). In mammals, lipid metabolism involves several organs, including the brain, adipose tissue, muscles, liver, and gut. These organs are part of complex homeostatic system and communicate through hormones, neurons and metabolites. Our study dissects the importance of mammalian Krüppel-like factors in over all energy homeostasis. Factors controlling energy metabolism are conserved between mammals and Caenorhabditis elegans providing a new and powerful strategy to delineate the molecular pathways that lead to metabolic disorder. The C. elegans intestine is our model system where genetics, molecular biology, and cell biology are used to identify and understand genes required in fat metabolism. Thus far, we have found an important role of C. elegans KLF in FA biosynthesis, mitochondrial proliferation, lipid secretion, and β-oxidation. The mechanism by which KLF controls these events in lipid metabolism is unknown. We have recently observed that C. elegans KLF-3 selectively acts on insulin components to regulate insulin pathway activity. There are many factors that control energy homeostasis and defects in this control system are implicated in the pathogenesis of human obesity and diabetes. In this review we are discussing a role of KLF in human metabolic regulation.

Child outdoor physical activity is reduced by prevalence of the Asian tiger mosquito, Aedes albopictus

We tested the hypothesis that day-biting mosquitoes contribute to child obesity by reducing opportunities for summer outdoor play. The influence of Asian tiger mosquito (Aedes albopictus) prevalence on child outdoor physical activity was compared in 2 matched urban communities, one treated for mosquito abatement and one untreated. More time was spent outdoors by children where abatement took place.

Host Penetration and Emergence Patterns of the Mosquito-Parasitic Mermithids Romanomermis iyengari and Strelkovimermis spiculatus (Nematoda: Mermithidae)

Romanomermis iyengari and Strelkovimermis spiculatus are mermithid nematodes that parasitize mosquito larvae. We describe host penetration and emergence patterns of Romanomermis iyengari and Strelkovimermis spiculatus in laboratory exposures against Culex pipiens pipiens larvae. The mermithid species differed in host penetration behavior, with R. iyengari juveniles attaching to the host integument before assuming a rigid penetration posture at the lateral thorax (66.7%) or abdominal segments V to VIII (33.3%). Strelkovimermis spiculatus attached first to a host hair in a coiled posture that provided a stable base for penetration, usually through the lateral thorax (83.3%). Superparasitism was reduced by discriminating against previously infected hosts, but R. iyengari's ability to avoid superparasitism declined at a higher inoculum rate. Host emergence was signaled by robust nematode movements that induced aberrant host swimming. Postparasites of R. iyengari usually emerged from the lateral prothorax (93.2%), whereas S. spiculatus emergence was peri-anal. In superparasitized hosts, emergence was initiated by males in R. iyengari and females in S. spiculatus; emergence was otherwise nearly synchronous. Protandry was observed in R. iyengari. The ability of S. spiculatus to sustain an optimal sex ratio suggested superior self-regulation. Mermithid penetration and emergence behaviors and sites may be supplementary clues for identification. Species differences could be useful in developing production and release strategies.

Efficacy of Duet dual-action adulticide against caged Aedes albopictus with the use of an ultra-low volume cold aerosol sprayer

Duet was field evaluated against caged Aedes albopictus, with the use of a truck-mounted ultra-low volume (ULV) cold aerosol sprayer at the rate of 90.6 ml/ha. Cages were placed in 3 rows stationed 30.5, 61.0, and 91.5 m downwind of the spray vehicle. Initial knockdown was >99% with mortality ranging between 95.8% and 98.0% across the distances. Volume median diameter (VMD) and droplet density were slightly reduced (16.4% and 18.6%, respectively) by distance. Reduction in VMD and droplet density, however, did not reduce mortality. The ULV application of Duet is an effective adulticide against Ae. albopictus and may be a useful tool for use in mosquito abatement programs.

Effects of insect growth regulators on the mosquito-parasitic nematode Romanomermis iyengari

Pyriproxyfen, a juvenile hormone analogue, diflubenzuron, a chitin synthesis inhibitor, and azadirachtin, an ecdysone agonist, are three insect growth regulators (IGRs) considered as selective and effective insecticides for mosquitoes. Romanomermis iyengari (Welch) is a mosquito-parasitic mermithid that can provide biological control against many medically important mosquito species. The compatibility of these two control tactics was tested by evaluating the sublethal effects of exposure to IGR on nematode developmental stages (preparasitic, parasitic, and preparasitic + parasitic) using Culex pipiens larvae as the host. Sublethal concentrations of IGRs were 90 % emergence inhibition of host mosquito. Preparasitic exposure to pyriproxyfen, azadirachtin, and diflurbenzuron had no effect on infectivity, parasite load, sex ratio, or male size but reduced nematode female length and increased male sex ratio at one parasite/larva. When IGRs treatments were made against the parasitic and preparasitic + parasitic stages, pyriproxyfen and azadirachtin reduced R. iyengari infectivity, parasite load, and male nematode length, whereas pyriproxyfen exposure increased male sex ratio and reduced the female R. iyengari length. Thus, IGRs have significant negative impacts on different stages of mosquito mermithid that can destabilize the balance of host-parasite population interaction. Therefore, IGRs should be used with caution in mosquito habitats where these parasites have established.

Host cues induce egg hatching and pre-parasitic foraging behaviour in the mosquito parasitic nematode, Strelkovimermis spiculatus

The responses of eggs in diapause and the infective stage of the nematode, Strelkovimermis spiculatus, to larvae of its host, Culex pipiens pipiens, were investigated in the laboratory. The results indicated that the presence of the host induced the egg hatching. The hatching rate increased when larger numbers of host larvae were present. Second instar mosquito larvae induced significantly higher hatching rates than any other stages. These findings explain how S. spiculatus synchronizes its life cycle with its host life cycle and population dynamics to increase its fitness when the natural habitat is constantly covered by water. Direct exposure of the nematode eggs to host larvae resulted in consumption of as many as 20 eggs per host. The eggs consumed caused 0-70% host mortality depending on the number consumed, which indicated an infection path other than cuticle penetration although it may represent a rare situation in nature. The result of host cue assays showed that the combination of chemical cues and physical vibration induced the highest egg hatching, which may increase the chance of host availability after hatching. However, once hatched, the nematodes ignored vibrations and used only chemical cues for host location. These findings suggest that eggs hatch synchronously with the most susceptible mosquito stage and with peak mosquito larval density.

Strain specific differences in intraspecific competition in Aedes albopictus (Diptera: Culicidae)

Malathion is an organophosphate insecticide that is used for the control of adult mosquitoes and agricultural pests. Recent studies have shown that malathion affects competition among mosquitoes in the larval stage. Individuals from laboratory colonies are often used in experiments but it is not known whether there is a difference between laboratory and field strains in their response to competition and malathion. Intraspecific larval competition in the presence of malathion (0.11 mg/liter) was compared between laboratory and field strains of Aedes albopictus (Skuse), a native of Asia that has established in the United States. There was no difference in the responses of the two strains to the presence of malathion. The fitness (finite growth rate) of the field strain decreased at the highest larval density tested but there was no difference in fitness across densities for the laboratory strain. This finding suggests that laboratory rearing could reduce sensitivity to crowding.

Willingness-to-pay for an area-wide integrated pest management program to control the Asian tiger mosquito in New Jersey

Using contingent valuation we estimated the perceived value of an area-wide integrated pest management program for the Asian tiger mosquito, Aedes albopictus, implemented in Monmouth and Mercer counties, NJ. We estimated residents' maximum willingness-to-pay and perceived monetary benefits (willingness-to-pay excluding residents who protested all types of payments) and payment modality through a telephone survey of 51 randomly selected households. The mean (+/- SE) perceived monetary benefits for an enhanced mosquito abatement program was $9.54 +/- 2.90 per capita per year. Most respondents would have been willing to pay through taxes (35%) or charitable donations (6%) starting then, or through one of these approaches in the future (43%), whereas 16% were completely unwilling to pay any additional costs whatsoever. We projected that the perceived monetary benefits to the counties' 1.01 million residents for an enhanced mosquito control program would be $9.61 million annually. Thus, collectively residents perceived monetary benefits of 3.67 times the combined 2008 annual operating costs of the counties' existing mosquito control programs of $2.61 million.

Larval mosquito habitat utilization and community dynamics of Aedes albopictus and Aedes japonicus (Diptera: Culicidae)

Aedes albopictus (Skuse) and Ae. japonicus (Theobald) are important container-inhabiting mosquitoes that transmit disease agents, outcompete native species, and continue to expand their range in the United States. Both species deposit eggs in natural and artificial containers and thrive in peridomestic environments. The goal of our study was to examine the types and characteristics of containers that are most productive for these species in the northeastern United States. In total, 306 containers were sampled in urban, suburban, and rural areas of New Jersey. Multiple biotic and abiotic factors were recorded in an attempt to identify variables associated with the productivity of each species. Based on pupal abundance and density of container types, results showed that tires, trash cans, and planter dishes were the most important containers for Ae. albopictus, while planter dishes were the most important containers for Ae. japonicus. Container color (black and gray), material (rubber), and type (tires) were correlated with species presence for Ae. albopictus and Ae. japonicus. These factors may play a role in the selection of oviposition sites by female mosquitoes or in the survival of their progeny. Differences in species composition and abundance were detected between areas classified as urban, suburban, and rural. In urban and suburban areas, Ae. albopictus was more abundant in container habitats than Ae. japonicus; however, Ae. japonicus was more abundant in rural areas, and when water temperatures were below 14 degrees C. Our results suggest many variables can influence the presence of Ae. albopictus and Ae. japonicus in container habitats in northeastern United States.

An autodissemination station for the transfer of an insect growth regulator to mosquito oviposition sites

A prototype autodissemination station to topically contaminate oviposition-seeking container-dwelling mosquitoes with the insect growth regulator, pyriproxyfen, was developed and tested in the laboratory. Our test subject was the Asian tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae), an urban species that colonizes small-volume cryptic larval habitats and is a skip ovipositor that visits multiple containers. The station consists of a water reservoir to attract gravid females, which is joined to a transfer chamber designed to contaminate visiting mosquitoes. The unit is easily constructed by moulding wet shredded cardboard using corn starch as a binder. The essential criteria that must be met to prove the efficacy of an autodissemination station require it to demonstrate effectiveness in attracting the target insect, in transferring the toxicant to the insect that will disperse the agent, and in facilitating the subsequent transfer of the toxicant from the insect to target habitats at a lethal concentration. Cage experiments demonstrated that the unit was readily accepted by gravid females as an oviposition site. A powder formulation of pyriproxyfen-impregnated silica particles adhered to visiting Ae. albopictus females (mean: 66 particles/female), although particles were lost over time. In cage (2.2 m(3) ) trials, pyriproxyfen-charged stations resulted in 100% inhibition of adult emergence, whereas in small-room (31.1 m(3) ) trials, 81% emergence inhibition was recorded. The venereal transfer of pyriproxyfen from contaminated males to virgin females was also observed, and pyriproxyfen was subsequently transferred to water-holding containers at concentrations that inhibited emergence. Key autodissemination station features include lack of maintenance requirements, biodegradable construction, low cost and low risk.

Submerged monoxenic culture medium development for Heterorhabditis bacteriophora and its symbiotic bacterium Photorhabdus luminescens: protein sources

Most medium formulations for improving culture of entomopathogenic nematodes (EPN) based on protein sources have used enriched media like animal feed such as dried egg yolk, lactalbumin, and liver extract, among other ingredients. Most results, however, showed unstable yields and longer production time. Many of the results do not show the detailed parameters of fermentation. Soy flour, cotton seed flour, corn gluten meal, casein powder, soytone, peptone, casein hydrolysates, and lactalbumin hydrolysate as protein sources were tested to determine the source to support optimal symbiotic bacteria and nematode growth. The protein hydrolysates selected did not improve bacterial cell mass compared with the yeast extract control, but soy flour was the best, showing 75.1% recovery and producing more bacterial cell number (1.4×10⁹/ml) than all other sources. The highest yield (1.85×10⁵ IJs/ml), yield coefficient (1.67×10⁶ IJs/g medium), and productivity (1.32×10⁷ IJs/l/day) were also achieved at enriched medium with soybean protein.

Area-wide management of Aedes albopictus: choice of study sites based on geospatial characteristics, socioeconomic factors and mosquito populations

BACKGROUND

Aedes (Stegomyia) albopictus (Skuse), the Asian tiger mosquito, is an introduced invasive species in the United States that is responsible for a significant proportion of service requests to local mosquito control programs. This container-utilizing mosquito is refractory to standard mosquito abatement measures in the United States. This study is part of a USDA-ARS project to develop an area-wide management strategy for Ae. albopictus. The goal was to identify three study sites, similar in socioeconomic parameters, geography and Ae. albopictus abundance, in urban and suburban areas in Mercer and Monmouth counties in New Jersey. Prior service requests and light trap counts and also detailed county maps were used to chose nine preliminary sites (four in Mercer and five in Monmouth) where weekly surveillance for Ae. albopictus was performed throughout the 2008 active season.

RESULTS

Although outliers were detected, socioeconomic variables in the study sites within each county were fairly consistent. Ae. albopictus abundance was associated with poverty levels and had the highest maxima in Mercer, although average mosquito abundance was similar in urban Mercer and suburban Monmouth.

CONCLUSION

Three study sites in each county were identified for future studies. The summer-long surveillance also revealed socioeconomic variables critical for the development of integrated mosquito management.

Source reduction behavior as an independent measurement of the impact of a public health education campaign in an integrated vector management program for the Asian tiger mosquito

The goal of this study was to evaluate the effectiveness of a public health educational campaign to reduce backyard mosquito-larval habitats. Three communities each, within two New Jersey counties, were randomly selected to receive: (1) both education and mosquito control, (2) education only, and (3) no education or mosquito control. Four separate educational events included a 5-day elementary school curriculum in the spring, and three door to door distributions of educational brochures. Before and after each educational event, the numbers of mosquito-larval container habitats were counted in 50 randomly selected homes per study area. Container surveys allowed us to measure source reduction behavior. Although we saw reductions in container habitats in sites receiving education, they were not significantly different from the control. Our results suggest that traditional passive means of public education, which were often considered the gold standard for mosquito control programs, are not sufficient to motivate residents to reduce backyard mosquito-larval habitats.