Maine CDC Press Release

September 1, 2009

Third Maine Horse Dies of Eastern Equine Encephalitis (EEE)

FOR MORE INFORMATION, PLEASE CONTACT:
Dora Anne Mills, MD, MPH
Phone: (207) 287-3270
Or Don Hoenig, DVM Phone: (207) 287-7615

AUGUSTA - The Maine Center for Disease Control and Prevention in the Maine Department of Health and Human Services and the Maine Department of Agriculture’s Animal Health and Industry Division announced today that a third horse in Maine has died of Eastern Equine Encephalitis (EEE).

EEE is a virus that is transmitted through the bite of an infected mosquito that has picked up the virus by feeding on an infected bird. The disease was first detected in Maine mammals in 2005 among two horses in York County, and was also found that year in some mosquitoes and birds in York and Cumberland Counties. Last October a man spending time in Cumberland County died of EEE. Earlier in August of this year, two horses in Waldo County were identified with EEE. Now a third horse that died recently in the Penobscot County town of Stetson has been identified with EEE. All three horses did not have updated vaccinations for the disease.

“Although the risk from one mosquito bite is very low, it now appears the risk of contracting EEE is geographically widespread,” said Dr. Dora Anne Mills, Director of the Maine CDC. “Since 2005, EEE has been detected in four Counties in Maine. We can assume other areas of the state have infected mosquitoes as well. Until we experience several deep frosts, it is important people take precautions.”

Steps people should take to protect themselves from EEE include:

  • Using an effective insect repellent on skin and clothing such as DEET or another EPA-registered repellent;
  • Covering up with long-sleeve shirts, pants and socks when outdoors;
  • Placing mosquito netting over infant carriers when outdoors with infants;
  • Being aware that mosquitoes are most active at dawn and dusk;
  • Cleaning up unnecessary standing water around the yard to reduce mosquito habitats; and
  • Vaccinating horses.

Although many persons infected with EEE have no apparent illness, those who develop symptoms do so usually 3 to 10 days after the bite of an infected mosquito. Symptoms range from mild flu-like illness to encephalitis, coma, and death. About one-third of those who have symptoms of EEE die. Approximately half of those identified with EEE and who survive will have permanent neurological damage. Unlike horses, there is no vaccine available for humans. There is also no known effective treatment.

The transmission cycle of EEE among birds and mosquitoes is most common in coastal areas and freshwater swamps. Human cases occur relatively infrequently, largely because the primary transmission cycle takes place in swamp areas where human populations tend to be limited. Those people at most risk are:

  • Residents of and visitors to endemic areas, especially near wetlands
  • People who engage in outdoor work and recreational activities
  • Persons over age 50 and younger than age 15 seem to be at greatest risk for developing severe disease

“It is especially important with schools starting that those schools near wetlands or taking field trips to wetlands assure parents and children are aware of the importance of protecting themselves,” cautioned Dr. Mills.

In horses, EEE is a highly fatal disease with mortality approaching 100 percent. Infected horses can exhibit clinical signs of illness within 3-10 days of being bitten by an infected mosquito. Clinical signs include unsteadiness, erratic behavior and a marked loss of coordination. There is no effective treatment and seizures resulting in death usually occur within 48-72 hours of an animal's first indications of illness.

“All horse owners should be sure their horses are current on their EEE vaccination, as this is a very effective vaccine,” reminded Dr. Don Hoenig, DVM, State Veterinarian. “All three of these horses were not vaccinated.”

Maine CDC is working with partners to trap and test mosquitoes in Waldo County as well as other areas of the state to help determine the geographical scope of the risk. Although EEE has been detected along the Eastern United States for a number of years, these recent cases in Maine are the farthest north the disease has been identified. Area Maine CDC staff are also working with municipalities and some local schools to inform them of the risks and of their options for controlling the mosquito population.

FMI

US CDC “Fight the Bite” Mosquito Website http://www.cdc.gov/ncidod/dvbid/westnile/prevention_info.htm

Maine CDC EEE Website http://www.maine.gov/dhhs/boh/ddc/epi/vector-borne/index.shtml

US CDC EEE Website http://www.cdc.gov/ncidod/dvbid/arbor/eeefact.htm

Maine Department of Agriculture Animal Health Website http://www.maine.gov/agriculture/ahi/index.html