Isik Unlu

Larval Mosquito Habitat Utilization and Community Dynamics of Aedes albopictus and Aedes japonicus (Diptera: Culicidae)

ABSTRACT 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°C Our results suggest many variables can influence the presence of Ae. albopictus and Ae. japonicus in container habitats in northeastern United States.

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.

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.

Crouching Tiger, Hidden Trouble: Urban Sources of Aedes albopictus (Diptera: Culicidae) Refractory to Source-Reduction

Our ultimate objective is to design cost-effective control strategies for Aedes albopictus, the Asian tiger mosquito, an important urban nuisance and disease vector that expanded worldwide during the last 40 years. We conducted mosquito larval surveys from May through October 2009 in the City of Trenton, New Jersey, USA, while performing intensive monthly source-reduction campaigns that involved removing, emptying, or treating all accessible containers with larvicides and pupicides. We examined patterns of occurrence of Ae. albopictus and Culex pipiens, another urban mosquito, among different container types by comparing observed and expected number of positive containers of each type. Expected use was based on the relative frequency of each container type in the environment. Aedes albopictus larvae and pupae were found significantly more often than expected in medium volumes of water in buckets and plant saucers but were rarely collected in small volumes of water found in trash items such as discarded cups and cans. They were also absent from large volumes of water such as in abandoned swimming pools and catch basins, although we consistently collected Cx. pipiens from those habitats. The frequency of Ae. albopictus in tires indicated rapid and extensive use of these ubiquitous urban containers. Standard larval-based indices did not correlate with adult catches in BG-Sentinel traps, but when based only on Ae. albopictus key containers (buckets, plant saucers, equipment with pockets of water, and tires) they did. Although we found that only 1.2% of the 20,039 water-holding containers examined contained immature Ae. albopictus (5.3% if only key containers were counted), adult populations were still above nuisance action thresholds six times during the 2009 mosquito season. We conclude that in urban New Jersey, effective source reduction for Ae. albopictus control will require scrupulous and repeated cleaning or treatment of everyday use containers and extensive homeowner collaboration.

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.

Effects of Biogents Sentinel Trap Field Placement on Capture Rates of Adult Asian Tiger Mosquitoes, Aedes albopictus

The Biogents® Sentinel (BGS) trap is the standard tool to monitor adult Aedes (Stegomyia) albopictus (Skuse) (Diptera: Culicidae), the Asian tiger mosquito. BGS traps are commonly placed in residential properties during surveillance operations, but locations within properties may have significant differences in ambient light, temperature, and humidity (e.g. between a sunlit lawn and shady underbrush). We examined the effect of BGS trap placement on Ae. albopictus capture rates in three residential properties in Monmouth County, New Jersey, USA. In each property we visually selected locations as shade, partial shade, and sun. Traps in “partial shade” locations were under vegetation and were exposed to filtered sunlight during some parts of the day while “shaded” locations were never exposed to direct sunlight. Locations defined as “sun” were exposed to direct sunlight for large parts of the day. We placed a BGS trap in each of the three location types and used small data loggers to measure temperature, relative humidity, and light exposure at each trap during a 24-hour deployment. To address temporal variability, we made seven separate measurements from 31 August to 22 September 2010. We found that “partial shade” and “full shade” locations did not differ but that “full sun” locations had significantly higher light exposure, higher temperature, and lower humidity. Importantly, Ae. albopictus catches (males, females, or both) were consistently and significantly over 3 times higher in traps located in shaded locations. To further investigate the effects of local temperature and humidity on surveillance we examined Ae. albopictus collections from 37 BGS traps fitted with data loggers and deployed weekly from August through mid October, during the 2009 season, in three urban sites in Mercer County, NJ. We confirmed that local climate influences capture rates and that Ae. albopictus surveillance projects need to monitor trap placement carefully for maximum efficiency.

Suppressing Aedes albopictus, an emerging vector of dengue and chikungunya viruses, by a novel combination of a monomolecular film and an insect-growth regulator.

The Asian tiger mosquito Aedes albopictus (Skuse) is rapidly increasing its global range and importance in transmission of chikungunya and dengue viruses. We tested pellet formulations of a monomolecular film (Agnique) and (S)-methoprene (Altosid) under laboratory and field conditions. In the laboratory, Agnique provided 80% control for 20 days, whereas Altosid, in combination with Agnique, provided 80% control for > 60 days. During field trials, the 1:1 pellet ratio of combined products provided > 95% control for at least 32 days and 50% control for at least 50 days. Altosid remained effective after a 107-day laboratory-induced drought, suggesting that the product serves as a means of control during drought conditions and against spring broods in temperate regions. Agnique and Altosid, when used in tandem for cryptic, difficult-to-treat locations, can provide long-term control of Ae. albopictus larvae and pupae. The possible additive or synergistic effects of the combined products deserve further investigation.

Experiences with the Large-Scale Operation of the Biogents Sentinel™ Trap

Abstract We obtained 160 Biogents Sentinel™ traps (BGS-traps) to monitor adult mosquito populations for the Area-wide Pest Management Program for the Asian tiger mosquito (Aedes albopictus) in New Jersey. We deployed between 90 and 110 BGS-traps weekly from May through October of 2008, 2009, 2010, and 2011. Here we detail our experience: challenges with acquisition, defects in construction, as well as actions taken to correct problems we found and preempt them in the future. Further, we describe the impact of these problems on our research and provide a cost analysis of repairs.

Evidence of Vertical Transmission of West Nile Virus in Field-Collected Mosquitoes

ABSTRACT: Male and nulliparous female mosquitoes were surveyed for evidence of vertical WNV infection in East Baton Rouge Parish, Louisiana. Adult male mosquitoes collected by trapping and aspiration, and adult male and nulliparous female mosquitoes reared from field-collected larvae were tested. Adult male Culex spp., female Aedes albopictus (Skuse), and female Culex quinquifasciatus Say mosquitoes that were collected as larvae were test-positive for WNV RNA. Infectious WNV was detected using virus isolation in field-collected male Aedes triseriatus Say and Culex salinarius Coquillett; these data represent the first field evidence of vertical transmission of WNV in Ae. triseriatus and Cx. salinarius.

Integrating the Public in Mosquito Management: Active Education by Community Peers Can Lead to Significant Reduction in Peridomestic Container Mosquito Habitats

Mosquito species that utilize peridomestic containers for immature development are commonly aggressive human biters, and because they often reach high abundance, create significant nuisance. One of these species, the Asian tiger mosquito Aedes albopictus, is an important vector of emerging infectious diseases, such as dengue, chikungunya, and Zika fevers. Integrated mosquito management (IMM) of Ae. albopictus is particularly difficult because it requires access to private yards in urban and suburban residences. It has become apparent that in the event of a public health concern due to this species, homeowners will have to be active participants in the control process by reducing mosquito habitats in their properties, an activity known as source reduction. However, limited attempts at quantifying the effect of source reduction by homeowners have had mixed results. Of note, many mosquito control programs in the US have some form of education outreach, however the primary approach is often passive focusing on the distribution of education materials as flyers. In 2010, we evaluated the use of active community peer education in a source reduction program, using AmeriCorps volunteers. The volunteers were mobilized over a 4-week period, in two areas with approximately 1,000 residences each in urban Mercer and suburban Monmouth counties in New Jersey, USA. The volunteers were first provided training on peridomestic mosquitoes and on basic approaches to reducing the number of container habitats for mosquito larvae in backyards. Within the two treatment areas the volunteers successfully engaged 758 separate homes. Repeated measures analysis of variance showed a significant reduction in container habitats in the sites where the volunteers actively engaged the community compared to untreated control areas in both counties. Our results suggest that active education using community peer educators can be an effective means of source reduction, and a critical tool in the arsenal against peridomestic mosquitoes.