Mosquito control in the Ocean State has undergone changes over the years, much as it has elsewhere in the U.S. The following is a synopsis of events that were gleaned from annual reports of the R.I. Agriculture Dept. (now the Div. of Agriculture in D.E.M.) and from interviews with several knowledgeable people. Passages in quotes are excerpts from the annual reports.
Times were tough in the 1930's. The federal Civil Works Administration (CWA) was formed to create labor for the many unemployed. One program was aimed at mosquito control. In November of 1933, the R.I. Agriculture Dept. (RIAD) received a letter from the U.S.D.A. Bureau of Entomology stating that the CWA had allotted funds to the Bureau for that purpose. The Bureau was requesting states' cooperation. RIAD accepted the proposal and "...a comprehensive program of ditching and other work for the extermination of this pest..." was developed. A "Director of Mosquito Extermination" was assigned and ditching work rapidly commenced - several hundred acres of salt marsh were drained by some 14 miles of ditches dug in the first two months of the program!
The extensive tracts of saltmarsh which fringe Narragansett Bay produce tremendous populations of three mosquito species. Monthly high tides flood the marsh, hatching the mosquito eggs that have been deposited in the "high marsh" - that zone which receives flooding only monthly. Ditches were designed to drain the marsh, lowering the water table so that depressions (which normally harbor the aquatic mosquito larvae) dry out, preventing larvae from completing their development to adults.
As requests from communities for drainage work mounted, the program was expanded and reorganized. Enactment of a state law in 1934 established a more permanent program. According to the new arrangement, "...mosquito projects are recommended by the health departments of the various cities or towns, approved by the local E.R.A. (Emergency Relief Administration) administrator and the Mayor or the President of the Town Council, the Director of Public Aid, and finally by the State Unemployment Relief Commission." Federal funds financed 30% of a project's costs, "...five elevenths of the remainder is paid by the city or town, and the balance from state funds."
Some 52 miles of ditches were dug in saltmarsh and cattail swamps during the 1934 - 35 period. Saltmarshes were ditched by a method developed by the State Reclamation Board of Massachusetts. First, two men worked a special double-bladed saw through the sod. Two other men then followed them with a 30 pound double-handled spade which cut blocks of sod measuring 10" wide, 24" deep, and 6" thick. Once leveraged upward, each block was pulled from the spade by a fifth man using a "California patented potato hook...". Blocks were piled alongside the ditch or used to fill depressions. Each man earned 5 cents per linear foot of ditch.
The ambitious drainage of the state's wetlands was not without controversy. Refering to "...interference with wildlife protection by mosquito work due to drainage..." the 1936 annual report notes that permanent ponds need not be drained because they support fish that prey on mosquitoes. By 1939, draining freshwater marshes was "...largely disontinued." Ponds were being created and "...stocked with fish to keep down mosquitoes (and) to serve as wildlife oases." Also, "Potholes in salt marshes (were) linked together to provide water circulation,...". Connecting depressions allows fish access to mosquito larvae.
That is one component of what is today referred to as Open Marsh Water Management (OMWM). OMWM is generally regarded as the best compromise for achieving long-term, low maintenance mosquito suppression while maintaining the integrity of the saltmarsh ecosystem. Today, an OMWM approach begins with an assessment of the existing natural and man-made elements in a marsh. Neglected ditches (partially clogged ditches often serve as mosquito nurseries) are either filled, reopened, or rerouted to connect low spots. Appropriate depressions are deepened to serve as fish reservoirs and the material removed may be used as fill for other areas. The design is such that normal tidal flow is restored and the water table is maintained.
By 1940, "The program for the eradication of mosquitoes in Rhode Island (was) facing difficulties." The WPA (Works Progress Administration) had expended some $1,800,000 but some towns were exhibiting a "...lack of cooperation on maintenance work...". "...the state refused to endorse new projects where old ones had not been maintained." A progressive program begun in 1939 trained WPA workers as mosquito inspectors. Some 700 inspectors spent 1940 mapping mosquito production sites throughout the state! The surveys pinpointed problem sites as targets for control efforts. This program represented an advancement over what had been, in many instances, indiscriminate drainage projects - evident today as hundreds of acres of saltmarshes are laced with miles of ditches. The straight, parallel pattern of the ditches suggests that little effort was expended on locating larval production sites. Obviously, the main goals were to put people to work and drain the marsh.
America's entrance into World War II had its effects on WPA programs. Most mosquito control projects ceased, although the fear of malaria and other mosquito-transmitted diseases being introduced from overseas by service personnel based at the Quonset Naval Air Station and Forts Getty and Wetherill on Jamestown Island led to a different program. A U.S. Public Health Service request resulted in a $300,000 federally funded, state-supervised WPA program "...to eliminate mosquito breeding places adjacent to defense areas." "...control plans involving salt marsh areas within five miles and fresh water areas within one and one-half miles of coastal defenses.." were drawn up. "Many pounds of Paris Green (an arsenic-containing compound) and dust mixtures and many gallons of No. 2 fuel oil were used..." near the military bases. The government's new emphasis on mosquitoes as disease-causing agents also prompted cities to rework ditches and destroy freshwater habitats that support species of Anopheles mosquitoes - vectors of malaria.
For some years following the war, many communities actively engaged in control programs, assissted by matching state funds. In 1951, 24 communities spent some $88,000 draining and filling areas, maintaining ditches, and spraying with fuel oil and "...New Jersey larvicide.". A five man state crew conducted mosquito control work on state lands and assisted cities on a matching fund basis. In 1950 this crew dispersed 120 gallons of DDT in kerosene on state lands and at sites such as Pawtucket Stadium and a Camp Fire Girls' Camp. The full-time crew, formed in 1947, was reorganized as a seasonal crew of 14 college students in 1954. The 1955 report notes a peak of 27 community mosquito control program.
The appearance of Eastern Equine Encephalitis (EEE) clearly boosted mosquito control activities at times in Rhode Island. 55 horse deaths were attributed to this mosquito-borne disease in 1938, and one pheasant farm lost over 3,000 birds to EEE in 1955. In 1956, the Agriculture Dept., the University of Rhode Island, and the newly formed Northeastern Mosquito Control Association sponsored a two-day forum at the University on mosquito ecology. That same year saw the return of EEE. "In spite of the truly epidemic proportions which (EEE) has reached in Rhode Island, we are most fortunate in escaping the tragic picture as presented in...Massachusetts where 13 human cases have been reported, and with practically no exception have had fatal termination." In 1957, the Regional EEE Investigation Laboratory was established in Taunton, Mass. For some years, mosquitoes collected in Rhode Island were delivered to that facility for EEE testing. The laboratory, established by the U.S. Public Health Service in the wake of the 1955-56 EEE episode, closed its doors in 1969 after 13 years during which viral activity was negligible. As fate would have it, 1970 ushered in a 6 year period of EEE activity in our area. In 1973, all but the most densely populated areas of Rhode Island were aerially sprayed with Malathion at a cost of nearly $250,000; 1.7 million acres in Massachusetts were sprayed that same year.
Community-level mosquito control in Rhode Island continued through 1973, but activity declined, apparently due to shrinking state support (the record is incomplete). The EEE events of 1973 apparently led to renewed adulticiding activity in communities. This prompted the state legislature, at the behest of environmental activists, to form the Mosquito Abatement Board to regulate indiscriminate control activities. In 1983, the first two reported human cases of EEE in Rhode Island occurred. One survived, but an infant lapsed into a coma and died one year later. This EEE episode prompted the state to create the position of Mosquito Abatement Coordinator (MAC) in D.E.M. Among other duties, the Coordinator conducts a surveillance program for the early detection of EEE. EEE was isolated from mosquitoes in 1990 and 1992 in the East Bay area. The EEE activity in 1990 resulted in a localized adulticiding program in Tiverton. There was a planned, localized adulticiding program in 1992 that was cancelled due to poor weather conditions and an early frost. The disease claimed the life of a 14 year old Rhode Island boy in 1993.
During the 1996 season, EEE infected mosquitoes were collected in 8 towns throughout the state (Charlestown, Hopkinton, Little Compton, North Smithfield, Richmond, South Kingstown, Tiverton, and Westerly). The majority of the viral activity was in the southern portion of the state with Westerly providing 42 of the state's 56 EEE isolations. Consequently, the entire town of Westerly was aerially sprayed with Resmethrin and a portion of Chapman Swamp in Westerly was aerially sprayed with an environmentally benign larvicide (Bacillus sphaericus). Additionally, many of the towns with EEE isolations initiated truck spraying operations targetting adult mosquitoes. Fortunately, no human cases of EEE were diagnosed in this higher than normal risk year; however, 2 emus in the town of Hopkinton died due to EEE infection.
In the 1997 and 1998 seasons, normal background levels of EEE were found in Rhode Island. However in 1998 there was one human fatality, and one confirmed horse death in 1997.
Community involvement in mosquito control has increased over the past several years as a result of a matching grant program that was initiated in 1990. Some $60,000 a year, a portion of pesticide registration fees paid by manufacturers, is earmarked for environmentally sound and progressive mosquito abatement projects. Awards are made on a competitive basis by the Mosquito Abatement Board and the program is administered by the MAC Office.
As of 1992, a EEE surveillance program has been conducted by the Mosquito Abatement Coordination (MAC) Office as follows. CDC light traps (baited with dry ice) are set weekly from mid-June until mosquito populations plummet in the fall. Traps are set on Monday evenings, retrieved Tuesday morning, and female mosquitoes are pooled into vials by species and site. The pools are delivered to the Rhode Island Health Department laboratory for viral testing. Pools are ground, filtered, and cultured on Vero cells. Pools exhibiting cytopathic effects are subjected to a specific ELISA test. EEE - positve pools are reported to the MAC Office via telephone approximately one week after the mosquitoes are trapped.
The current responses to viral isolations are as follows. When Highlands J (HJ) virus or EEE virus are detected in an endemic vector species (primarily bird-biting Culiseta spp.), trap numbers are increased in that area and appropriate press releases are issued. When EEE virus is detected in epidemic vector species (primarily mammal-biting Aedes, Coquillettidia and Culex spp.) or animal (horse, emu, and other exotic birds) or human cases are reported, trapping is increased, press releases follow, school and/or other public officials are notified, and an EEE Committee meets to consider further actions. Adulticiding via a truck-mounted ULV unit is considered as a local response. If warranted, aerial adulticiding is contracted and financed by R.I. Department of Health emergency funds. Responses vary depending on the season, weather, population trends, location of the isolation, pool size, and other pertinent factors. Arrangements are currently being made for broad-scale aerial larviciding to occur as preemptive suppression tactics.