Risk of Eastern Equine Encephalitis in New Hampshire high this year, and may be higher in 2010

070329_eastern_equine_encephalitis_genericNew Hampshire  11/08/09  eagletribune.com:  More mosquito batches tested positive for Eastern Equine Encephalitis in New Hampshire this year than ever before.  Add to that the fact the state tested considerably fewer batches than in years past, and it adds up to a bad year for the presence of EEE in the Granite State. And it could mean another bad year ahead in 2010.  The only good news is there was only one human case of EEE this year — a 3-year-old from Candia who survived.

“It was way, way higher than it ever has been before,” said Alan Eaton, an entomologist with the University of New Hampshire Cooperative Extension.  He said some of that increase could be attributed to the way the state tested this year — but not all.  “It suggests to me the risk this year was the highest since we have been keeping records, 2003 or 2004,” Eaton said.

This year, 73 mosquito batches tested positive for EEE, according to Beth Daly of the state Department of Health and Human Services. That compares to eight positive batches last year and just six in 2007. And, interestingly, the state tested far fewer batches this year, Daly said.  “We tested significantly less — 3,887 tested pools,” she said. “The last couple of years, we’re been testing around 10,000 or more. We lost federal funding and get no state funding, so we did more targeted testing.”

The state targeted mosquito species most likely to test positive, so although they tested fewer batches, the testing was more efficient, Daly said. Regardless, the numbers bear out a high level of EEE presence in New Hampshire in 2009.  “We may have expected more human cases … but it’s hard to extrapolate,” Daly said. “We certainly had human-biting mosquitoes that tested positive. We were probably lucky.”EEE Mosquito 2

Eaton would like to think the state’s single human case of EEE this year means residents have become better educated about the risks associated with mosquitoes and have begun to take precautions to protect themselves.  That means using insect repellent, scheduling fall athletic events earlier in the day or on Saturday morning, spraying mosquito larvae and adults, and reducing standing water.

“I hope it’s because people are listening now,” Eaton said. “To me, this is an example of empowerment. By giving people a little bit of information, you empower them to reduce their risk and you can reduce risk tremendously by what you do.”  He said the numbers bear that out. In 2005, only 15 mosquito batches tested positive in New Hampshire, but there were seven human cases, including two deaths. That’s a big difference from this year’s 73 positive batches and single human case of EEE.

But it’s more about the percentage of positive batches, according to Eaton. This year, 0.018 percent of batches tested were positive. That sounds like a small percentage, but it’s a huge increase over 2008, when just 0.00079 percent of batches tested were positive. There were no human cases of EEE last year.

Seven animals — two alpacas, three horses, a llama and an emu — tested positive for EEE this year. There was just one animal case last year. Also unusual this year were six canaries in Rochester that tested positive for EEE.  The state has stopped testing birds for EEE, Daly said, and never tested canaries. But this group was different, she said.

“If requested to do so for specific veterinary purposes, we might test birds,” she said. “This was a large group of outdoor canaries. They were housed outdoors. The veterinarian had requested EEE testing. Given the fact so many died within a particular flock, we agreed to test.”  Daly said the state has found testing birds is not a useful signal for the presence of EEE, although they used to test hundreds of birds a year.

thumbnailCAGGY500The state had no reported presence of West Nile virus this year and just a single mosquito batch tested positive for that disease in 2008. But there’s no quick answer as to why that is, she said.  “We’ve never had a lot of West Nile activity,” she said. “We have had human cases, but they were not believed to be locally acquired.”

What this year’s results portend for next year isn’t clear, but it’s probably not good.  “EEE is very difficult to predict,” Daly said.  The loss of federal funding this year translated into the loss of two positions — a surveillance coordinator and a lab technician.  The state has applied to the federal government for the funding again and if it’s restored, would fill those two openings, Daly said. That would allow the state to “ramp up” testing next year, she said, do more investigation and data collection.

Daly was reluctant to forecast what 2010 might bring, and Eaton agreed it’s a tough thing to do.  “To some degree, I think the high incidence of positives suggests we might get a higher-than-average year next year — and we should brace ourselves,” he said.  But a lot of questions remain unanswered, including how EEE overwinters, he said. He and others in the field will gather later this year to analyze data and try to draw some conclusions.

Thirty-two New Hampshire municipalities had positive mosquito pools this year, Daly said. Those towns included Derry, Windham, Atkinson, Plaistow, Newton, Kingston, Danville and Sandown. Rockingham County continues to be the center of EEE activity in the state.  “Rockingham County has been the heaviest risk area for a good long time,” Eaton said. “There are some factors we think we know contribute to that and others are open to question.”  One thing experts do know is that the county offers the ideal habitat for larvae in the species of mosquito that spreads EEE in the bird population. But lots of other questions remain unanswered, he said.


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