Yale Bulletin and Calendar

July 19-August 23, 1999

Volume 27, Number 35

Entomologist verifies immigrant
mosquito's arrival in state

The buzz among Connecticut entomologists is that there's a new species of mosquito in the state, and the earliest known evidence of the insects' arrival is now in the collections of the Peabody Museum of Natural History.

This most recent insect immigrant is the Aedes (Finlaya) japonicus, or Japanese Rock Pool mosquito. It is one of only two mosquito species known to have been introduced recently into the United States from Asia, according to Yale entomologist Leonard Munstermann, curator of entomology for the Peabody Museum and a research scientist in the School of Medicine's department of epidemiology and public health (EPH)

Scientists in Long Island, New York, and Colliers Mill, New Jersey, reported last August and September that they had found specimens of Aedes japonicus in their respective states.

Because of these reports, Munstermann and fellow entomologist Theodore Andreadis of the Connecticut Agricultural Experiment Station surveyed tire dumps in this state for the insect's larvae. (Discarded tires in which rain water has collected are popular breeding grounds for this species of mosquito, explains Munstermann.) The entomologists discovered evidence of Aedes japonicus larva in four sites in Connecticut: North Haven, Bloomfield, Portland and Essex.

Meanwhile, while learning more about the East Asian mosquito, Munstermann began to sense that the insect was very familiar. "I realized that I had seen it before," he says.

The Yale scientist, who has for years gathered samples of the flying, crawling and digging creatures inhabiting his backyard in suburban Hamden, began looking through his private collection and discovered that he had indeed seen Aedes japonicus before: Two adult specimens of the mosquito were among the insects he'd gathered in June of 1998, two months before the discovery of the insects in New York and New Jersey. "I just hadn't paid much attention to them before," he says. Those specimens are now part of the Peabody's entomology collections.

Scientists are still uncertain about how Aedes japonicus made its way from Asia to the United States, notes Munstermann. One strong possibility is that the mosquitoes' eggs were inside discarded tires that were later shipped overseas, says the Yale scientist, noting, "There's a big used tire trade from Asia to the United States." However, this is just a hypothesis, he notes, adding, "We still have a lot of detective work ahead of us."

Only female mosquitoes bite and suck blood; they use the proteins in the blood to produce eggs. While mosquito larvae can develop in a variety of water habitats, those of the Aedes japonicus are found in small water containers, such as holes in rocks or trees, as well as the aforementioned used tires or other containers. Although many mosquitoes are most active at dusk or dawn, Aedes japonicus is a daytime feeder and is usually associated with wooded areas.

Around the world, mosquitoes are responsible for transmitting many serious infectious diseases, notes Munstermann, who studies the biology of mosquitoes and sandflies (another group of important disease carriers) in his laboratory at EPH. Yet, of the approximately 3,000 species of mosquitoes in the world, "only 100 or so are documented transmitters of disease," explains the entomologist, and most of those species are associated with a specific disease -- such as malaria, for instance.

Scientists are continually testing different kinds of mosquito species to determine their potential for being infected by and transmitting serious diseases, especially their ability to serve as a "bridge vector" carrying diseases between different species of animals, explains Munstermann.

Japanese scientists reported 50 years ago that Aedes japonicus had the potential to transmit Japanese B encephalitis. In more recent experiments, Aedes japonicus have shown high infection rates, efficient transmission and the ability to pass on viruses from the mother mosquito to her progeny.

Studies in Japan of Aedes japonicus adults collected in the field showed that, under laboratory conditions, the mosquitoes fed readily on both viremic chicks and suckling mice. This, combined with the species' proven eagerness to feed on humans, means it may be possible for Aedes japonicus to transfer bird viruses, such as the deadly EEE (Eastern Equine Encephalitis), to humans, says Munstermann. However, there is no reason to panic, he says. The Connecticut Department of Public Health reports that, of the 45 species of mosquitoes in Connecticut, only a handful have been linked to outbreaks of EEE -- and that those outbreaks occurred in other states. In fact, according to the state health department, there has been no documented human case of EEE in Connecticut.

Whether or not Aedes japonicus does prove capable of transmitting EEE, "we probably will not suffer any immediate health consequences from the presence of the mosquito in this state," says Munstermann.

A sampling of the interesting and unusual creatures that entomologist Leonard Munstermann has gathered near his home in the past few years is now on view in the "Backyard Biodiversity" display in the lobby of the Peabody Museum of Natural History, 170 Whitney Ave.

-- By LuAnn Bishop

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