The mosquito issue in Connecticut has generally had two components: one the nuisance factor and, two, the thankfully never realized human health issues associated with mosquito-borne disease. Until this past season, the disease of concern has been Eastern Equine Encephalitis (EEE); and as we are here today to recognize, we now need to be similarly concerned about West Nile or a West Nile-like Encephalitis (WNV). Recent findings notwithstanding, it is still fair to say that the risk of EEE or WNV transmission to humans is low. However, we need to review our understanding of that risk, evaluate our approach to comprehensive mosquito surveillance and control, and adjust our program as necessary.
Organized mosquito control in Connecticut began in 1902 in response to hundreds of malaria cases reported from many coastal communities. The program was part of the Connecticut Agricultural Experiment Station (CAES) in New Haven. Operational control of mosquitoes consisted of hand ditching of tidal wetlands for drainage and application of pesticides and oils to kill mosquito larvae. Systematic "grid-ditching" climaxed in the early 1930's with the formation of the Civilian Conservation Corps. Some 90% of original Atlantic coast tidal wetlands from Maine to Virginia were altered in this fashion.
The virus that causes Eastern Equine Encephalitis (EEE) was first identified in 1938 in Massachusetts, although horse and human deaths in the region symptomatic of this disease had occurred prior to the isolation of this virus. Outbreaks of EEE have occurred sporadically among horses and domestic pheasants in Connecticut since 1938 but no human cases nave ever been confirmed. In 1949, the mosquito control responsibilities were transferred to the Department of Public Health (DPH) primarily to maintain the tidal grid ditch network. With the advent of environmental awareness in the 1970's and 1980's, mosquito control evolved into a more natural resource oriented, interdisciplinary program coordinated with wetland and watercourse management. Because of this progressive approach to mosquito management, when in 1993 the Mosquito and Vector Control Section was eliminated from the DPH due to budgetary constraints, it was transferred to the Department of Environmental Protection (DEP) to function as a wetlands restoration unit. In 1996,with the identification of high incidence of EEE in human-biting mosquitoes in southeastern Connecticut, the DEP along with the Connecticut Agricultural Experiment Station (CAES) and DPH responded on an emergency basis. The following legislative session under the leadership of Governor Rowland and then Commissioner Holbrook, state funds were appropriated to institute and support the current Mosquito Management Program.
Connecticut's Approach to Mosquito Management
The state's Mosquito Management Plan is a public health-based monitoring and management collaboration involving the DEP, the CAES, and the DPH, which includes the systematic monitoring of mosquito breeding populations; monitoring the prevalence of disease within those populations; application of pesticides to control populations; communication and provision of technical assistance to municipalities regarding mosquito control. The program is coordinated by the DEP which is responsible for the systematic identification and monitoring of mosquito breeding sites, the provision of technical assistance to municipalities and private property owners regarding mosquito control, and the collection and communication of information and data. Long term mosquito breeding site management occurs through DEP's wetland restoration program.
The CAES, in consultation with DEP, identifies the locations for traps, conducts the trapping, identifies mosquitoes by species and conducts arbovirus testing. Trapping has been conducted in areas known or suspected to support mosquito populations which have historically tested positive for EEE, are capable of supporting such populations, or are proximate to locations where EEE-related horse deaths have occurred. Additional trap sites were established this past season in response to the identification of WNV and will inform the identification of additional trap sites this coming season.
The DPH reviews all mosquito test data and consults with the DEP and CAES regarding the epidemiological significance of such results. Based upon its evaluation of the potential human health risks, DPH advises as to appropriate personal, municipal, and state actions to reduce such risks. DPH also maintains direct communication with local health directors and the state veterinarian as necessary to evaluate and advise on mosquito borne disease issues. This season, DPH played an active and invaluable role as the State's liaison with neighboring state's health departments as well as the CDC.
Increased efforts in response to West Nile virus
This summer when human cases of West Nile virus were detected in New York City, the Mosquito Management team immediately responded. Working together and guided by our Eastern Equine Encephalitis Contingency Plan, with ad hoc modifications based upon the breaking revelations of the new virus, this team
-- identified and implemented the strategic deployment of additional mosquito traps to augment existing traps and track the existence of this mosquito borne virus in lower Fairfield County;
-- determined appropriate locations and methods of spraying adulticide and applying larvicide to control mosquito populations while minimizing any adverse impacts of pesticide application;
-- conducted the spraying of a low toxicity, narrow band pesticide specifically targeted to mosquitoes and sprayed to maximize reduction of potential reservoirs of virus;
-- established an effective communications system with all local officials simultaneously to advise and consult on all actions affecting their communities and to effectuate communication with the public;
-- maintained continuous communication with the federal Centers for Disease Control (CDC) and neighboring state officials;
-- established a protocol for the collection and sampling of dead birds associated with the virus
It is important to note that because we had an existing monitoring and surveillance program already in place, we were able to be responsive rather than reactive. We relied on the data provided by the additional population monitoring to guide our decision as to where to conduct spray operations to provide the most control with the least risk to human health. Moreover, because of the scientific data available, we were able to make the decision to ground spray vs. aerial spray, further reducing the potential exposure of humans to pesticides.
Looking towards the Future
Towns in lower Fairfield and New Haven counties have expressed deep concern about West Nile virus and would like to see continued and additional efforts made to prevent any public health threat. Traditionally, the southwestern corner of Connecticut has had little arbovirus activity because it is highly urbanized. However, West Nile virus appears to be an urban disease; the primary vector (Culex pipiens) is an urban mosquito and both have been found in the most densely populated area of the state.
At a recent conference, the CDC indicated that an intensive monitoring program for WNV should be undertaken in this upcoming year and should include monitoring of the crow population (as a sentinel), monitoring of the human population and increased monitoring of the mosquito population. Also, monitoring of larval mosquito populations and preventative control through education, source reduction and the use of larvicides would reduce the adult mosquito vector population and potentially reduce the need for and extent of adulticides. Connecticut's team of experts is reviewing these recommendations and evaluating the efficacy of their implementation. The DEP has and will continue to provide technical assistance to towns and can increase operational mosquito control efforts in southwest Fairfield County. We are also aware of the concerns regarding increased pesticide use and are committed to continue our practice of a reasoned, measured response to the mosquito borne disease issue as well as a continued evaluation of pesticide usage.
All this must be done while maintaining the program of mosquito trapping and testing throughout the state. EEE remains a concern in our region and we cannot forsake this effort.
There is the potential for federal action in two areas. First, we look for the continued support and encouragement of the CDC and the National Wildlife Disease Center. The continued participation of the CDC in evaluating the health risks associated with mosquito-borne viruses and its assistance in public information and outreach regarding those risks provides a voice of expertise and credibility beyond that which individual states may be able to provide alone. Second, here in Connecticut we rely on wetland and habitat management as a natural mosquito management tool. Additional federal resources and support of our wetland restoration program would also be most welcome and could provide direct benefits to coastal communities beyond those associated solely with reduced mosquito populations.