West Nile cases in U.S. up nearly a third in latest week: CDC
(Reuters) – The number of U.S. cases of West Nile virus climbed by nearly a third in the latest week as the spread of mosquito-borne disease accelerated and threatened to make the 2012 outbreak among the most severe on record, government figures showed on Wednesday.
So far this year, 2,636 cases have been reported to federal health officials, up from 1,993 reported the week before, the Centers for Disease Control and Prevention said in its weekly update of outbreak data. A total of 118 people have died from the disease, compared with 87 reported one week ago.
The disease has been reported in people, birds or mosquitoes in 48 U.S. states, so far absent only in Alaska and Hawaii.
Texas accounted for about 40 percent of all human cases. Two-thirds of the cases have cropped up in six states – Texas, Louisiana, South Dakota, Mississippi, Michigan and Oklahoma.
Of the cases reported to the CDC this year, 1,405, or 53 percent, are of the severe neuroinvasive form of the disease, which can lead to meningitis and encephalitis.
The milder form of the disease causes flu-like symptoms and is rarely lethal.
West Nile outbreaks tend to be unpredictable. Hot temperatures, rainfall amounts and ecological factors such as the bird and mosquito populations have to align just right to trigger an outbreak like the one this year.
The CDC said the number of cases this year is the highest reported to federal health officials through the second week in September since 2003, the worst year on record.
The disease is thought to have originated in Africa and was first detected in New York City in 1999.
This year’s outbreak already is more than three times the size of last year’s, when 712 cases were reported nationally, with 43 deaths.
(Reporting by Paul Thomasch; Editing by Bill Trott)
US, Canada Sign Great Lakes Agreement
WASHINGTON, D.C. – U.S. Environmental Protection Agency Administrator Lisa P. Jackson and Canada’s Minister of the Environment Peter Kent today signed the newly amended Great Lakes Water Quality Agreement at a formal ceremony in Washington, D.C. First signed in 1972 and last amended in 1987, the Great Lakes Water Quality Agreement is a model of binational cooperation to protect the world’s largest surface freshwater system and the health of the surrounding communities.
“Protecting cherished water bodies like the Great Lakes is not only about environmental conservation. It’s also about protecting the health of the families—and the economies—of the local communities that depend on those water bodies for so much, every day,” said Administrator Jackson. “The amended Great Lakes Water Quality Agreement we signed today outlines the strong commitment the U.S. and Canada share to safeguard the largest freshwater system in the world. Our collaborative efforts stand to benefit millions of families on both sides of the border.”
“Joint stewardship of the Great Lakes—a treasured natural resource, a critical source of drinking water, essential to transportation, and the foundation for billions of dollars in trade, agriculture, recreation and other sectors—is a cornerstone of the Canada-United States relationship,” said Minister Kent. “The Great Lakes Water Quality Agreement supports our shared responsibility to restore and protect this critical resource, and builds on 40 years of binational success.”
The revised agreement will facilitate United States and Canadian action on threats to Great Lakes water quality and includes strengthened measures to anticipate and prevent ecological harm. New provisions address aquatic invasive species, habitat degradation and the effects of climate change, and support continued work on existing threats to people’s health and the environment in the Great Lakes Basin such as harmful algae, toxic chemicals, and discharges from vessels.
The overall purpose of the Agreement is “to restore and maintain the chemical, physical and biological integrity of the waters” of the Great Lakes and the portion of the St. Lawrence River that includes the Canada-United States border. Both governments sought extensive input from stakeholders before and throughout the negotiations to amend the Agreement. Additionally, the amended Agreement expands opportunities for public participation on Great Lakes issues.
The amended agreement sets out a shared vision for a healthy and prosperous Great Lakes region, in which the waters of the Great Lakes enhance the livelihoods of present and future generations of Americans and Canadians.
A Case for Stormwater and Mosquito Management
Federal mandate as amended in the Clean Water Act (CWA) in 1987 requires the development and implementation of stormwater management programs by all states to abate problems with runoff and other nonpoint-source pollution (Metzger 2004). Although the CWA regulations and recommendations address sediment and other environmental problems associated with the runoff of surface waters entering local waterways, surprisingly and collectively, they do not address public health issues such as the production of habitat for nuisance and disease-carrying insects such as mosquitoes. Although public health and safety is a major component of all stormwater management programs, mosquito management has been overlooked. In fact, an informal nationwide survey of state stormwater regulations including some sort of strategy or action plan to deal with mosquito control revealed that of the limited information available most has been developed through mosquito control agencies, through university involvement, or on a county-by-county basis.
Since initial reports of West Nile virus in 1999, public awareness and concern have increased dramatically regarding the risks associated with mosquito abundance. Because stormwater management ponds or best management practices (BMPs) hold standing water, their potential as mosquito breeding habitat is high; consequently, their design and maintenance is important in reducing public health risks and concern associated with West Nile and other arthropod-borne viruses (arboviruses). The primary functions of stormwater management BMPs include 1) the retention of water to reduce or remove pollutant runoff from impervious surfaces such as roads, sidewalks, and roofs; 2) the provision of flood control during storm events, thereby preventing or minimizing damage to public and private property; and 3) the impediment or slowing of stormwater flow or runoff in order to reduce streambank erosion and suspended sediment loads in adjacent or nearby streams. Relatively recent changes regarding water-quality impoundment in the National Pollutant Discharge Elimination System (NPDES) Phase II stormwater regulations mandate have caused concern among municipalities, developers, environmental land-planning firms, and property owners with respect to mosquito and human health–related issues.
Stormwater Management in Maryland
The Chesapeake Bay Initiatives in 1984 included the development of Maryland’s original stormwater management program to control flooding into local streams (Comstock and Wallis 2003). At that time, Maryland became the first state to adopt stormwater-quality regulations (MDE & Center for Watershed Protection 2000). The dogma in the mid-1980s was that if runoff flooding from the increase of development were controlled, water quality of receiving streams would be maintained. Therefore, the State of Maryland specified in the original code of Maryland Regulations that stormwater management be focused on flood control (Comstock and Wallis 2003). Since this time, stormwater management has evolved significantly in Maryland due in large part to the contributions of several state agencies focused on identifying necessary improvements on the original statute that was designed for water-pollution control.
The Maryland Department of the Environment (MDE) developed a two-volume stormwater design manual to address three objectives: 1) control the quality of stormwater runoff due to urbanization; 2) provide more effective methodologies for stormwater management (BMPs) in new development sites; and 3) improve the quality of BMPs and maintain a high level of functioning in the state. Moreover, this approach would promote environmentally sustainable or “green” development techniques that would closely mimic natural processes—thereby reducing the dependence on formal structural management intervention techniques to deal with increases in stormwater runoff. While this manual would serve as a source of stormwater design information for regulatory agencies in Maryland and other states, it was lacking a significant component dealing with public health—namely, mosquito control strategies. Despite the presence of already-established mosquito-transmitted viruses (e.g., eastern equine and LaCrosse encephalitis) in the US, as well as the increasing risk of a new insect-transmitted virus, West Nile virus (WNV), the Maryland State Highway Administration (MDSHA) was the state agency ahead of the curve in this respect by expressing interest in developing stormwater management strategies that incorporated a multiyear mosquito surveillance component coupled with mosquito abatement to determine which BMPs not only were most influential in accomplishing all three goals of the MDE manual but also reduced the potential for mosquito activity related to nuisance and disease transmission concerns.
From a medical perspective, mosquitoes are arguably the most important group of insects in terms of both economic and health costs worldwide to humans and animals. They are responsible for transmitting a wide array of viruses (e.g., West Nile virus, eastern equine encephalitis, dengue); protists (e.g., malarial Plasmodium); and nematodes (dog heartworm). To date, of the approximately 3,500 species of mosquitoes that exist worldwide, 174 species are in North America, with roughly 60 of these inhabiting the state of Maryland. Without exception, all mosquitoes require an aquatic habitat such as a pond, marsh, treehole, tire, natural or artificial container, crabhole, or artificially created system such as a stormwater BMP in which to rear the larval stage (Laird 1988) (Figure 1). Mosquito larvae possess structures (siphons) that allow them to breathe atmospheric oxygen. Mosquito larvae, in general, filter-feed particles from the water column. Some are predators, but for the most part, larvae feed on organic debris that is either suspended in the water column or floating at the water surface. Larvae do not and cannot transmit any disease-causing organism.
With adult mosquitoes, it is the female that requires a blood meal in order to provide protein necessary for egg yolk production and egg laying. However, not all mosquitoes require blood to produce eggs; some species barely feed or perhaps feed on nectar before laying a batch of eggs. Among those that do require a blood meal, some feed exclusively on frogs, birds, or mammals. There are some mosquito species (e.g., Aedes vexans and Aedes albopictus) that feed both on birds and mammals; from a vector ecology perspective, these species are defined as bridge vectors. It is the populations of these species that require greatest vigilance, as they are responsible for bridging the gap between the WNV-infected bird communities and uninfected mammals (e.g., horses and humans).Host location for blood meals is facilitated by flight. Mosquitoes can fly 0.5 to 1 mile for a blood meal. It is this behavior that has facilitated the evolution of many disease-causing or pathogenic organisms such as viruses, protozoa, and filarial worms. At certain times of the year, in many areas of the United States, mosquitoes are formidable nuisance biting insects. Considering these dispersal capabilities, managing stormwater BMPs for mosquito activity may appear daunting if management involves abatement strategies for adults. However, many mosquitoes that are nuisance biters and are not important vectors of WNV or other arboviruses do not utilize stormwater BMPs as their larval habitat. Thus, because complaints of nuisance biting mosquitoes and concern about WNV transmission may involve those mosquitoes not inhabiting stormwater BMPs, abatement or control should focus on the larval stage—that is, the developmental period during which the mosquito larvae reside in a stormwater BMP filled with water.
As a result of the rapid spread of WNV across the United States as well as the tremendous economic and health impact it has had on human and horse populations, the focus of mosquito abatement and control programs to regulate mosquito populations quickly turned to stormwater management BMPs. The control of mosquitoes in either the larval or the adult stages involves the application of pesticides, some chemical and some biological. Such pesticide use is federally regulated under the Federal Insecticide, Fungicide, and Rodenticide Act within the guidelines of the CWA. In 2002, the House Subcommittee on Water Resources and Environment convened a hearing to discuss the CWA and mosquito control. However, rulings on several cases have resulted in mixed interpretations of the current legal situation in terms of communities’, industry’s, and any other private or public entity’s use of pesticides with regard to the restrictions of the CWA. In light of this problem, the Division of Emergency and Environmental Health Services (within the Centers for Disease Control and Prevention) has suggested a more integrated systems-based approach to control mosquitoes when designing stormwater management facilities (www.cdc.gov/ncidod/dvbid/westnile/index.htm).
The significant increase of West Nile virus across the United States and especially in Maryland warrants a more thorough understanding of larval habitats in terms of the role that anthropogenic habitats such as stormwater ponds play in this mosquito-borne public health issue. Long-term (multiyear) studies are lacking with respect to understanding how larval mosquito population dynamics change from year to year as stormwater management BMPs evolve with time.
Based on the preliminary results of a pilot study, a more thorough surveillance program of five stormwater BMPs (shallow marshes, retention ponds, detention ponds including extended detention basins, infiltration basins, and trenches) was established for an additional two years and divided into two phases, a surveillance phase and a control phase. Because climatological conditions vary from year to year and stormwater BMPs change or evolve over time, it is unknown how larval mosquito populations might change as well. Therefore it is critical to maintain monitoring efforts to more fully understand this relationship.
This project incorporated a multiyear (temporal) perspective and a spatially diverse component encompassing four counties: Baltimore, Howard, Montgomery, and Prince George’s counties in Maryland (Figure 2). The MDSHA included BMPs in this study that were along roads and highways in wooded habitats; in urban and suburban habitats; in industrial sections; and near schools, hospitals, nursing and assisted-living homes, and residential neighborhoods. The underlying goal of assessing BMPs located adjacent or in close proximity to human populations at risk of WNV infection and those not at risk would allow the MDSHA to better formulate BMP design and mosquito control to minimize public health concerns for these subpopulations. Thus, the objectives for the surveillance phase included 1) an assessment of larval and adult mosquito diversity among the identified BMPs and 2) a comparison of the spatial and temporal distributions of mosquito larvae among these types of stormwater BMPs. The primary objectives for the control phase were 1) to initiate an abatement program and determine the efficacy of larval control among the types of stormwater BMPs examined in this study; 2) to train MDSHA personnel on mosquito sampling to determine efficacy of control application; and 3) to provide an integrated pest management program for the MDSHA. Such a program would serve as a model or template for other county stormwater habitat management decisions as they relate to mosquito surveillance and control.
In 2003, the MDSHA initiated a preliminary study on three types of stormwater BMPs: shallow marshes or wet ponds, retention ponds, and detention/extended detention ponds (Figure 3). During the study, biweekly monitoring of larval and adult mosquito populations associated with these BMPs was conducted from June through September (Figure 4). It was anticipated that the outcome of this study would create a better understanding of mosquito population dynamics temporally (over the mosquito-breeding season) and spatially (among different types of BMPs) and that it would lead to a more efficient and thorough surveillance and control program to minimize public health concerns as well as cost and maintenance issues associated with mosquito management. The intent was to use this first season as a fact-finding mission to more thoroughly address with a longer-term study.
Due to a number of factors that can influence mosquito abundance and diversity, such as inter- and intra-BMP type variation with respect to microhabitat for mosquito larvae, differences in maintenance schedules of BMPs, microclimate differences among BMP types, variation in the amount and location of precipitation, and BMP functionality, preliminary results suggested that increased rigor (via increasing the number of BMP replicates and types, as well as number of seasons) would be needed to track mosquito population dynamics more accurately. What was learned about these types of BMPs was that during the surveillance phase, mosquito diversity varies among BMP type and that populations of those mosquito species important in arbovirus transmission fluctuate depending on the amount of precipitation and rate of water filtering by each BMP type. Moreover, adult mosquito sampling provided important evidence that some nuisance mosquito species may be collected from close proximity to any given BMP; however, that does not imply that the adults emerged from larvae inhabiting these BMPs. This is an important piece of information to understand when dealing with public complaints about BMPs being potential reservoirs for mosquitoes and resulting concerns about transmission of West Nile virus.
In developing a control or abatement system for the MDSHA stormwater management program, it was clear from the control phase of this first year that if source reduction via water-level reduction does not occur in a timely rate, control methods should focus on reducing larval populations. Representative BMPs were selected as treatment sites using a larvicide, Bs (Bacillus sphaericus), that specifically targets the insect order Diptera, including mosquito larvae. Other BMPs served as control or nontreatment sites (Figure 5). This particular larvicidal treatment has through rigorous scientific studies been shown to be environmentally friendly as it occurs naturally in the environment but not normally in aquatic systems. It can be applied by properly trained technicians in the field or subcontracted out to private companies, and it, along with a close relative, Bti (Bacillus thuringiensis var. israelensis), is commonly used in larval mosquito abatement programs throughout the United States. Preliminary results indicated that larval control was possible and most cost-efficient with the types of BMPs examined during this pilot year. Because only one control event was implemented, additional events would help support the contention that larval numbers can be reduced and reduction can be maintained in order to reduce nuisance levels of flying adult mosquitoes.
Mosquitoes and BMPs: Results of an Additional Two-Year Study
The pilot study in 2004 provided a strong foundation to build upon for 2004–2005 with special focus on increasing the statistical rigor of the project by increasing the number of replicates per BMP from three to five as well as increasing the number of types of BMPs (from three to five, adding infiltration basins and trenches) for all aspects of the study including surveillance and control (Figure 6). These modifications allowed for a more complete understanding of the mosquito diversity among BMPs and the relevance of this diversity to public health concerns (Table 1).
The surveillance phase of the study over the next two years revealed that increases in mosquito abundance (quantified by number of larvae per dip, based on 50 dips per sampling date along the periphery of each BMP) among counties were reflected by increases along the path of isolated occurrences of major rain events. This underscores the importance for stormwater managers to track the path of major precipitation events, such as thunderstorms and especially tropical storms and hurricanes, to be able to focus mosquito surveillance on BMPs located along such paths. Interestingly, the majority of species listed in Table 1 are not of major importance in terms of vectoring most of the arboviruses, including WNV, in the United States. Within the BMPs studied over this two-year period, those primary species responsible for vectoring WNV among birds include Culex pipiens and Culex restuans. Aedes vexans and possibly Culex salinarius may be those species most likely responsible for bridging the feeding gap between birds and mammals, thereby facilitating transmission movement from birds to mammals (including humans). Conducting larval monitoring or surveillance on each BMP over two years has provided valuable data on how the percentage of these “target” species populations fluctuate over a mosquito season (June through September) in both years (Figures 7 though 11).
Mosquito abatement efforts in 2004 provided between 98% and 100% reduction of mosquito larvae in treated versus untreated BMPs (Table 2). These findings corroborated those of 2003 but also show that, when necessary, larval mosquitoes can be controlled efficiently and inexpensively to determine efficacies of treatments. In 2005, precipitation was so scattered that it prohibited any control operations.
Lessons Learned Over Time
Since mosquito-borne illnesses in the United States have largely been eliminated as a health risk (while their vectors remain), Americans have not regarded these diseases as a threat until the recent introduction and very rapid spread of West Nile virus changed this view. Educating the public on how to reduce larval mosquito habitat (source reduction) has been of greatest priority to reduce the threat of WNV and other mosquito-borne diseases through the efforts of state mosquito control associations, state environmental agencies, and private mosquito control businesses. The Federal Clean Water Act as interpreted under the NPDES requirements was established to improve the nation’s clean water supply by developing systems to deal with surface runoff created from storm events. Because of increased development and increased amounts of impervious road surfaces, stormwater has become one of the leading causes of water pollution nationwide. NPDES has increased restrictions and presented serious issues to agencies dealing with stormwater management. The MDSHA has been one of a few agencies interested in addressing the issue of stormwater management and mosquito surveillance and control so that important management decisions on stormwater BMP design and construction can be based on empirical scientific research focused on larval mosquito population dynamics and can incorporate strategies to minimize mosquito production and issues related to mosquito nuisance and mosquito-borne illnesses such as WNV.
Many statewide mosquito-surveillance programs and in some cases privately consulted projects do not incorporate rigorous spatial or temporal components in their monitoring efforts. That is, sometimes surveillance sites are selected because of convenience and/or logistical issues and the selection is not based on valid scientific inquiry designed to address specific management questions. This project illustrates why, clearly, conclusions from such programs can be premature and reckless from a legal perspective. This type of inefficient monitoring needs to be avoided. For example, the pilot study in 2003 allowed a preliminary yet scientifically rigorous understanding to unfold relative to which mosquito species inhabited three types of BMPs as well as their population dynamics over a complete field season (June through September). Although certain stormwater BMPs in Maryland at certain times of the year or those exposed to heavy precipitation can arguably be large producers of mosquitoes, the pilot study provided initial data indicating that those mosquito species implicated in the transmission of WNV among birds and mammals do not on average make up a significant percentage of those collected per dip.
Many times the general public associates biting adult mosquitoes with a particular marsh or accumulation of water, such as any of the BMPs used in Maryland. It is imperative for stormwater managers to understand that adult mosquitoes will fly at times great distances for a blood meal; consequently, people located near BMPs receiving mosquito bites will accuse BMPs through guilt by association with nearby biting mosquito populations. Moreover, not all mosquitoes are vectors of disease-causing agents, so to attempt to manage all mosquitoes is a waste of time and resources. In addition, mosquitoes found to be positive for WNV might actually not be a competent vector of the virus; therefore, it is critical to understand the mosquito ecology for a region before management decisions are made.
Likewise, because stormwater management is federally mandated, it may be that mosquito abatement programs will have to accompany design and construction, as well as maintenance, of future stormwater projects. The decision to control larval mosquitoes in this project was based on several reasons: 1) environmental safety—i.e., the use of biological larvicides was much more environmentally friendly, less visible, and of less cause for concern for the general public; 2) less training was required; 3) there were cost-benefit advantages—i.e., while the larvicide chosen (Bacillus sphaericus) was more expensive, the residual time or the duration it remains effective is longer, translating into future treatments to BMPs; and 4) the MDSHA was responsible only for those larvae produced in BMPs, not for transient adult mosquitoes on MDSHA property. It would be unreasonable for the MDSHA or any other stormwater management agency to be responsible for controlling those adults breeding in other types of habitats away from the BMPs.
Integrated Pest Management Program:
A Template for the Future
In order to comprehend the dynamics of how and why West Nile virus has increased to epidemic proportions among birds and has threatened certain human populations in a relatively short time period, and to develop an integrated pest management strategy to control mosquito populations, ensuring public health policies, an understanding of larval mosquito biology is needed (Mostashari et al. 1999; Peterson, Macedo, and Davis 2006). It has been suggested that control and prevention of mosquito-borne illnesses such as West Nile virus and other related viruses should be grounded in a well-established integrated mosquito management program at the local level (Nasci 2002). However, such programs tend to not be based on empirical research local to the region and may not address the specific needs of the locality. I would recommend that local-level programs be derived from research studies such as the one described here in order to meet such needs in a more cost-effective and relevant manner. Based on the results from this study, I would like to make the following recommendations to ensure that future stormwater/mosquito management programs incorporate a systems-based approach:
•Identify BMPs already constructed that are in close proximity to hospitals, schools, and retirement homes and establish regular maintenance programs such as cleaning litter, removing floating and emergent vegetation, and regularly mowing the periphery.
•Before constructing new BMPs, consider design options for structures regarding slope of the basin (slow-moving water will deter mosquitoes from laying eggs) and slope of the banks (generally, BMPs in this study with steep banks tended to not have as much emergent vegetation and did not produce large numbers of mosquitoes).
•Contrary to other recommendations suggesting that dry detention ponds be maintained to ensure complete drainage within 72 hours, I would recommend that BMPs be constructed either as shallow marshes or as retention ponds, as long as they serve the purpose from a water-quality perspective. This study indicates that detention/extended detention ponds as well as infiltration basins left unmaintained behaved similarly to detention ponds, producing large numbers of WNV bird- and mammal-feeding mosquito species. It is the intermittent wet/dry periods that attract these species of mosquitoes. Shallow marshes and retention ponds produced mostly those mosquito species that play minor or no roles in the transmission of WNV. If detention ponds and infiltration basins are required, periodic mosquito monitoring of those near populated areas is recommended. Perhaps hybrid BMPs that allow a wetpond element, extended detention component, and a wetland element (Downey 2003) may address the issues stated above. Anecdotal evidence over the span of this project has shown that BMP types that have evolved to hold water indefinitely or are shallow marshes generally have a higher abundance of natural predators (such as dragonfly larvae and water scorpions/predacious water bugs) of larval mosquitoes. On average, these ponds typically had lower numbers of those mosquito species that are important as disease vectors. Therefore, it is recommended that stormwater managers using stormwater BMPs that hold water 72 hours or less or display numerous wet/dry periods should move away from this type of BMP and incorporate instead BMP designs that minimize larval survival, such as steep banks, minimal emergent vegetation, and systems that do not experience several wet/dry cycles over a summer season.
•Monitor weather fronts and precipitation amounts, especially if storms are heavy in areas near detention ponds and infiltration basins. These BMPs typically experience wet/dry periods that promote outbreaks of Aedes vexans and Culex pipiens, both species important in vectoring WNV among birds and mammals. In the event heavy precipitation does occur around areas with these types of BMPs, stormwater managers should monitor these sites for the presence of mosquito larvae.
•Make resources available to train technicians to recognize mosquito larvae and pursue training/certification programs for pesticide application so they can treat BMPs as needed. Mosquito control in many states is administered by the Department of Agriculture or Department of Environmental Protection in addition to the Department of Health, and these agencies may provide training in these areas.
•Threshold levels for treatment should be established by one of two methods. One is by field sampling and determining when larval numbers exceed an average of 20 larvae per dip based on a 50-dip minimum of the BMP in question. (This number was established based on anecdotal evidence that when larval numbers were this high, typically flying and biting adults were abundant.) The other method for establishing threshold levels for treatment is by monitoring the number of formal complaints by the public or by maintenance workers responsible for ongoing maintenance and operation of BMP facilities. It is not imperative that all BMPs be treated with bacterial larvicides, only those identified through monitoring or complaint calls.
•If pesticide use is required, there are many options available, both chemical and biological, to control larval mosquitoes. However, the bacterial larvicides used in this study provided an effective, environmentally friendly, and cost-effective approach to control mosquitoes in Maryland BMPs. Therefore, it is recommended to use either Bti or Bs, as these bacterial larvicides will effectively control mosquito larvae and not harm water quality or non-target invertebrates significantly.
•Provide a phone number for the general public to call to provide information regarding BMPs with mosquito nuisance problems. This will empower individuals and allow open communication between the general public as well as allow them to feel they are working with stormwater managers for their own benefit.
In the past five years, with the exception of a few studies (Banks 2004; Kluh et al. 2002; Metzger et al. 2002), very little work published has involved empirical research to address the applied needs of the private sector with regard to stormwater and mosquito management. The intention of this article is to provide additional relevant scientific research directed toward not only improving stormwater management but also reducing public health concerns with regards to mosquito-transmitted diseases, by providing a systems-based set of recommendations to manage both mosquitoes and stormwater. In the real world, stormwater must be managed, and unfortunately, in doing so, mosquito habitat is created. Understanding mosquito ecology as well as the human ecological aspects associated with the creation of artificial systems to manage stormwater runoff is best attained by integrating science with industry when it comes to stormwater BMP design, maintenance, and management.
Natural systems holding water on a permanent basis rather than temporarily have figured out a way not only to maintain water quality but also to regulate problem mosquito species populations. It is believed through current stormwater management dogma that if water is filtered through a system quickly (a minimum of 72 hours, based on federal mandates), then larval mosquitoes will run out of water—i.e., habitat—before completing their life cycle. However, this regular wetting and drying of stormwater basins provides excellent opportunities for those species, such as one of the potential bridge vectors of WNV, Aedes vexans, that have co-evolved with temporary aquatic systems to exploit these types of BMPs. If development continues to increase, if the amount of impervious surface covering our landscape continues to increase, and at the same time if available acreage to manage the associated increase in stormwater runoff is decreasing, then maybe filtering stormwater and dumping it into our stream systems in a short period of time—as with detention ponds and infiltration basins—is not the best approach. Perhaps a better approach would involve systems that are based on multiple recommendations that are economically, environmentally, and aesthetically efficient and sustainable.
Author’s Bio: John R. Wallace, Ph.D., is an associate professor of biology at Millersville University in Millersville, PA