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Al Gettman, Ph.D.
URI East Farm
(401) 789-6280

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Did You Know? get fresh

There are 46 different species of mosquito in Rhode Island.

A principal duty of the Mosquito Abatement Coordination (MAC) Office is to conduct surveillance of mosquito-borne diseases as an early warning system. Adult mosquitoes are trapped statewide weekly from June through September. Samples are then tested at the RI Health Department Laboratory for the presence of Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV). Appropriate responses are based on those results.

The MAC Office assists communities with efforts to reduce the human risk of WNV. Since 2000 (the year WNV arrived in RI) the state has been providing product to communities to be distributed into underground storm-water catchment basins. This effort reduces mosquito production from that habitat one that is well known to produce mosquitoes that are important in transmitting WNV. Low Ground Pressure machines

The MAC Office also conducts salt marsh water management projects with specialized low-ground-pressure machines. This effort alters water flow such that predation of mosquito larvae by fish is enhanced. The MAC Office partners with other agencies and organizations as well, in conducting salt marsh restoration projects.

Want to know how you can help control the spread of WNV and EEE? Read on.

Mosquitoes in Rhode Island

Rhode Island is home to 46 different species!

Life cycle

While both male and female mosquitoes need nectar for sustenance, only the female requires a blood meal, which is needed for egg production. Several days after ingesting the meal, a batch of up to 250 eggs is laid. Some species lay egg "rafts" on the water surface which hatch in two days. Other species deposit eggs above the water surface, around the edges of depressions. These eggs can remain viable for months and hatch when flooded.

The next stage after the egg hatches is the larval stage. During this stage, the larvae "wiggle" in the water and will go through four developmental stages where they will shed their skin or "molt". They filter-feed and breathe at the surface. The larval stages last from five days to several months, depending on several factors. Larvae then become the non-feeding pupal stage, which lasts for several days before adults emerge.

Aquatic Habitats

Immature stages can occur in a variety of aquatic habitats including salt marshes, freshwater swamps, woodland pools, retention ponds, abandoned swimming pools and artificial containers. For this reason, it is important that homeowners do not permit stagnant water to collect in backyard containers -- buckets, clogged gutters, forgotten glasses and pool covers are common examples -- as several important disease-transmitting species are readily produced in these habitats. One cup (8 oz.) of stagnant water can breed hundreds of mosquitoes.

Immature stages do not occur in flowing water, and are generally absent from permanent bodies of water, which tend to support a variety of predatory creatures. Finally, the immature stages of many species only occur in particular habitats. For example, species that occur in salt marshes do not occur in backyard artificial containers, and vice-versa.

For more information, visit the following sites:

Mosquito-Borne Diseases in RI

Eastern Equine Encephalitis (EEE) and West Nile Virus (WNV) are the two human diseases transmitted by mosquitoes in RI. Both are maintained in bird populations in nature. Mosquito species that bite both birds and mammals acquire these diseases from birds and can then transmit them to humans. EEE has a very high human mortality, but fortunately is very rare. WNV has a very low human mortality, but has become prevalent in both rural and urban environments since its establishment in RI in 2000.

The most effective way to reduce the risk of acquiring EEE and WNV is to reduce exposure to mosquito bites. Mosquito biting is more prevalent at dawn and dusk, in the shade and at temperatures above 55 degrees. Wearing protective clothing and using repellents containing DEET are effective ways for reducing risk. Finally, it is important to maintain screens and prevent stagnant water from collecting in artificial containers around the home.

For more information, visit the following sites:

Salt Marsh Water Management

Narragansett Bay and the islands are fringed by some 3,600 acres of salt marsh which provide many valuable functions. Unfortunately, two species of mosquitoes can be produced in tremendous numbers from this habitat. Large "broods" of adults can occur following the highest monthly tides, which hatch eggs that were deposited in the higher elevations of the marsh. Water management projects involve altering the water regime to reduce stagnant pools, and to enhance predation of larvae by fish.

Many acres of RI salt marshes have been degraded due to human intervention. Roadways, dikes, undersized culverts and excess runoff from adjacent upland development have altered the tidal regime and soil salinity, such that undesirable invasive plant species thrive. The MAC Office partners with other agencies and organizations on projects aimed at restoring salt marshes utilizing water management and other techniques.

For more information, visit the following sites:

For General Information 222-6800 • After Hours Emergencies 222-3070 • Disclaimer
rev. 7/23/14