YDN Staff Reporter
The high prevalence of infected Rhode Island mosquitoes prompted Connecticut officials to begin testing in the eastern part of the state in early September. Rhode Island officials discovered the high rate of infection during yearly mosquito surveillance in August, a procedure Connecticut Governor John Rowland abolished after assuming office two years ago.
Two scientists from the Connecticut Agricultural Experiment Station, Drs. Theodore Andreadis and John Anderson, began trapping Connecticut mosquitoes two weeks ago. Shirley Tirrell-Peck at the Yale Arbovirus Research Unit at the public health school analyzes cell cultures of the collected mosquitoes to determine the danger the disease poses to state residents.
So far in Connecticut, there have been no reported cases of the disease, which has a 50 percent fatality rate, but the symptoms -- headache and fever -- are nonspecific, so investigators are unsure if anyone has died from equine encephalitis this year. The Conn. State Department of Health recently set up a
mechanism to look into emergency rooms at state hospitals to see if cases do occur.
Robert Ryder, director of Infectious Diseases at the Yale Department of Epidemiology and Public Health, said the virus is usually found in one in a thousand mosquitoes. But this year, the virus was found in one in a hundred Rhode Island mosquitoes. In addition, the virus, usually found only in swamp mosquitoes, has spread to five or six different species which
are more likely to bite humans.
"The likelihood of encountering the virus goes up ten-fold," Ryder said.
To determine the rate of infection, Andreadis and Anderson trap and freeze mosquitoes from eastern Connecticut. They send the frozen mosquitoes to Yale's Arbovirus Research Unit, where they are ground up and injected into Vero cells, cultured from the kidneys of African monkeys. If a virus is present, the cells show symptoms within seven days.
"Yale has been criticized for having creepy viruses around," Ryder said. But "had we not been here, we could not have helped the state."
The results of testing done on Connecticut mosquitoes have been much more favorable than those of Rhode Island. Tirrell-Peck said the virus is much less prevalent in Connecticut than in its eastern neighbor, where officials are currently spraying a pesticide to kill the deadly mosquitoes.
"Barn Island in the Stonington township is the only exception," added Tirrell-Peck, who is the sole researcher in charge of analyzing the mosquito culture cells.
The percentage of infected mosquitoes in Connecticut is still higher than usual. Dr. Leonard Munstermann of the Yale School of Public Health said the Agricultural Station is currently collecting mosquitoes from other parts of the state, and, if necessary, will spray infected areas. But once the first frost comes, danger is abated.
"If it gets cold, no more mosquitoes are flying, and they can't bite humans," Munstermann said.