PITTSFIELD -- It's mid-winter but city Board of Health and county mosquito control officials are planning a stepped-up campaign of trapping, testing, insecticide treatment and public education in response to the presence of disease-carrying mosquitoes here last summer.
Christopher Horton, superintendent of the Berkshire County Mosquito Control Project, who met with the health board this week, laid out the results of the testing and treatment program during 2012, which he described as "an epic season."
Mosquito testing statistics for the past warm season showed that 29 insect tests in the seven Berkshire County communities the program serves were positive for West Nile virus and two were positive for Eastern Equine Encephalitis, Horton said during a presentation to health board members.
Of those, both encephalitis hits and 12 West Nile ones were in Pittsfield.
"We found all kinds of things we didn't expect were going to be there," Horton said.
He said the positive findings were three times the state average and placed Pittsfield among cities considered in a "high risk" zone on a state Department of Public Health map -- the only community so designated in Berkshire County. That was in part because there was one human case of West Nile here, Horton said.
In the Berkshire communities involved in the mosquito program, there was only one insect test in 2011 that was positive for West Nile virus, in Sheffield, and none for EEE.
In most human cases of West Nile, people won't even know they have it. About 1 in 5 will have headaches, fever, body aches and vomiting, while about 1 percent of all infected patients could develop a severe illness. There were 30 confirmed cases in Massachusetts last year. EEE is rare, but causes a headache, stiff neck, and lethargy, or death in about half of all or cases. Only about 100 cases of EEE have been confirmed in Massachusetts since 1938, seven of which were confirmed in 2012.
Interim health board Chairwoman Roberta "Bobbi" Orsi asked whether the program of testing and insecticide treatments should begin earlier in light of the statistics from 2012. She and other board members said they prefer public education and remedial steps like draining standing water sites and treating drainage catch basins or other sites with larvicide, rather than spaying for adult mosquitoes.
"Spraying should be the last resort," she said.
Horton said the April-through-October program ideally follows a process of testing before treatment, in part so that workers know "where the hot spots are," and spraying in problem areas as needed.
He said the goal is not to eliminate all disease-carrying mosquitoes -- an impossibility -- but to trap and test the insects continually to detect signs of disease and then to react quickly. The program seeks to "break up the cycle" of infection, he said, which can also be passed to and be carried by birds. Their flight allows disease to spread over a wider area and potentially infect humans.
All aspects of the program, including spraying for adult mosquitoes, are important to controlling the insects and the diseases they can carry, he said, and they work best together. The focus is on sites near human populations, not on remote areas of the city or county towns.
Beginning in late March, there is testing in known areas of standing water and in drainage system catch basins, of which there are about 6,000 in Pittsfield, and those with standing water are treated with a larvicide. Horton said the number was lower last year because of dry weather but more than 3,400 catch basins were treated.
Mosquito larvicides also can be used in an area with standing water, he said, and workers typically will remove obstructions to allow the water to begin flowing or drain from the area.
The two seasonal crew members and Horton constantly perform remediation work in wet areas, working to drain them if possible. The program works with conservation officials and has permission to perform work by hand in wetlands, Horton said.
Spraying for adult mosquitoes is primarily done in a radius around areas where disease-carrying mosquitoes were found. The application is 0.62 ounces per acre of a rapidly dissipating pyrethrin class insecticide, he said.
Horton said a federal Environmental Protection Agency study recently found no ill effects for humans from the insecticide type, which is an organic compound made from crushed chrysanthemum leaves -- and lately from synthetics.
Since the beginning of the county program, spraying has been controversial, and many communities, including Pittsfield, dropped the service when Berkshire County government was eliminated in the late 1980s. Pittsfield rejoined the program in 2010, he said, after a bad year for mosquitoes in 2009.
Describing the 2012 season, Horton said 226 "pools" of mosquitoes from Berkshire County were tested at state DPH labs in Boston. Testing consists of compressing batches of 50 mosquitoes each and testing them for DNA evidence of disease.
The program here will receive new mosquito traps that lure them with carbon dioxide and vacuum them into a container. The CO2 release simulates the breath of an animal or person.
Older traps contain a mixture of standing water that also vacuums the insects inside when they land to lay eggs. Horton said a mosquito will first feed on a host and draw blood before laying eggs, so the trap is likely to detect disease if it is present in an area.
New detailed maps of the county that overlay aerial photographs also will be used to chart the areas where disease is detected and to keep track of insecticide applications and the dates and times, he said.
Because of the possibility of a recurrence of disease-carrying mosquitoes, spraying to reduce nuisance mosquito swarms -- a longtime staple of the program -- could be limited this year. "Nuisance spraying will be on the back burner," Horton said.
Beaver dams in Pittsfield are another concern, he said. Of the sites where disease was detected in mosquitoes, most were where beavers had created shallow areas of standing water. Some were drained by program crews in cooperation with wildlife officials.
"Beaver mediation in this city is a huge issue," he said.
Orsi also expressed concern about the beaver activity: "I think more needs to be done with that. It sounds like an increasing problem."
The mosquito control program in the county has a budget of $208,000, Horton said. About half of that is spent in Pittsfield under a state formula based on population and other factors. The funding comes in the form of state aid to communities.
To reach Jim Therrien:
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