New England Public Radio

Public Health Officials Say Horses Should be Vaccinated For EEE and West Nile Virus

The warmer weather means spring is finally here, but it also means mosquito season is around the corner. Public health officials in New England are urging horse owners to begin vaccinating their animals now for mosquito borne illnesses like West Nile Virus and the more serious Eastern equine encephalitis (EEE).

Massachusetts state veterinarian Catherine Brown says these diseases can be fatal.

“Unlike in humans, there are good vaccines available for animals,” Brown says. “So it’s a reasonable recommendation to encourage horse owners to vaccinate their animals to protect them from these diseases which we know will occur at some point this summer.”

Brown says although a vaccine was developed for humans, it’s for experimental use only, which is why people should take precautions against mosquito bites such as wearing long sleeves and using insect repellent.

Last year, nine people and six horses were diagnosed with a mosquito-borne illness in Massachusetts. Symptoms of West Nile Virus can range from a mild fever to severe muscle weakness but it rarely causes death, while EEE has a 40 percent fatality rate.

Hard Frost in Western Massachusetts Spells End to Mosquito-Borne Illness Season

The season for mosquito-borne illnesses in western Massachusetts is all but over after much of the region received a hard frost over the weekend. Even with mild temperatures in the days since the frost, it was enough to kill off most adult mosquitos.

Dry weather has contributed to a lower than normal mosquito population this year says Chris Horton, superintendent of the Berkshire County Mosquito Control Project. But, Horton says, that low population produced high numbers of mosquito-borne illnesses. And, he says, the record heat over the summer could have contributed too.

“When you have extra hot conditions, the chance of virus being transmitted between mosquito and bird is higher.”

Both West Nile Virus and Eastern Equine Encephalitis (EEE) are spread from infected birds to humans through mosquito bites. All told, 22 human cases of West Nile have been confirmed in the state so far this year, and seven human cases of EEE. That’s well above last year’s numbers when the state saw six cases of West Nile and two  cases of EEE. Horton says now that a frost has hit much of the region, the risk of encountering an infected mosquito is essentially gone, but even with winter approaching, the mosquitos themselves are not.

“There are different species of mosquitos. Some will over-winter as adults, some will over-winter as larvae, and some could over-winter as eggs, and next spring, as soon as the snow melts, it’ll start all over again.”

Many schools and municipalities in the region had limited evening outdoor activities while the risk of mosquito-borne illnesses remained high earlier this fall. After Saturday’s frost, many organizations have lifted those limitations, including UMass Amherst. 

 

 
 

A Warm Fall Could Extend Mosquito Season, Threat of Mosquito-bourne Illnesses

The threat of the mosquito-bourne illnesses West Nile Virus and Eastern Equine Encephalitis have caused many communities in western Massachusetts to limit evening outdoor activities until the first hard frost. But that hard frost could come later than usual this year.

Michael Rawlins, manager of the Climate System Research Center at UMass Amherst, says because of general warming patterns in the northeast, current prediction models call for warmer than average temperatures through October and November. If temperatures stay warm he says, that could delay the first hard frost by one or two weeks, which would extend the mosquito season.

“That said, weather variability plays a large role. We could easily have a really cold snap that lasts a day or two that would give us that hard freeze, and then the mosquitos are basically done.”

Rawlins says mosquito season has already been longer than usual this year due to the abnormally warm spring. He says though precipitation has been fairly average so far this year, a spike in rainfall could produce even more mosquitos.

“If we were to get a lot of rain over a period of a week or so, let’s say two to three inches, and the ground gets really wet, a lot of standing water, that may allow a lot more mosquito larvae to hatch and create even more of a problem.”

The state Department of Public Health has raised the risk-level for mosquito-bourne illnesses to “critical” in five communities in western Massachusetts. They are Athol, Belchertown, Chicopee, Orange, and Royalston. Many other communities, including Springfield, Holyoke, Northampton, Amherst, and Pittsfield have a “high” risk level for the viruses.