Lower threshold to consider aerial spraying against mosquitoes, among other changes

BOSTON — The Massachusetts Department of Public Health (DPH) today announced several revisions to its Guidelines for Phased Response to Eastern Equine Encephalitis (EEE) as recommended by an expert panel convened by DPH earlier this year. The changes to the guidelines include lowering the specific conditions under which health officials consider the use of aerial spraying against mosquitoes; adjusting the range of factors that classify “high” risk; and a move towards more focal and targeted use of aerial spraying of insecticide.

“EEE and other mosquito-borne illnesses represent a serious public health concern for Massachusetts families,” said DPH Commissioner John Auerbach. “These revised guidelines will ensure that we mount the most effective, science-based approach to reduce the risk of disease spread by mosquitoes among our residents.”

In response to indications that risk from EEE may be increasing, this past winter DPH convened a panel of external authorities and experts to review and comment on the current EEE surveillance and response plan. The panel included nationally-recognized experts in the fields of mosquito control, toxicology, ecology, climate change, public health, and infectious disease, as well as representation from local public health in southeastern Massachusetts — the area hardest hit by EEE.

The recommendation of the panel were reviewed by all state agencies involved in EEE prevention and response, including the Department of Agricultural Resources, Department of Fish and Game, Department of Conservation and Recreation, and the Department of Environmental Protection, and have been incorporated into the 2012 Massachusetts Arbovirus Surveillance and Response Plan under the section “Guidelines for Phased Response to EEE Surveillance Data.” They include:

  • Lowering the threshold for considering aerial spraying from “Critical” to “High”, the second-highest classification for risk.
  • Adjusting the factors that indicate “High” and “Critical” risk. Risk level will be classified as “High” when one mammal-biting EEE-infected mosquito has been found; the current guidelines indicate a “High” level of risk only after two such mosquitoes have been found. The second key revision is to reduce from two to one the number of human or mammal cases of EEE required to indicate “Critical” risk.
  • Considering options for more targeted, focal area aerial spraying as an alternative to full regional spraying, and exploring potential local assets and airplane-based equipment to support more rapid and focused aerial spraying activities.

Aerial spraying is just one aspect of the state’s multi-pronged approach to reduce the impact of EEE illness in Massachusetts. The type of insecticide used in aerial spraying has been selected after careful consideration due to its efficacy in killing mosquitoes while posing minimal risk to humans.

“These changes represent a balanced and responsible approach to addressing EEE that will protect the public health while preserving natural resources,” said Department of Environmental Protection Commissioner Kenneth L. Kimmel.

Personal prevention methods continue to be the most effective way to prevent mosquito-borne illness. They include using mosquito repellent spray featuring DEET, covering up when outdoors at the peak mosquito hours of dusk and dawn, repairing window and door screens to keep mosquitoes from getting indoors, and removing sources of standing water around the house and yard which can serve as mosquito breeding grounds.

Arboviruses in Massachusetts: mass.gov/mosquito-borne-diseases