Lyme diseases cases spiked by 50 percent in Dutchess in 2017

The number of Lyme disease cases reported in Dutchess County last year jumped by 50 percent compared to the year before, reaching the third-highest total on record in the state.

If the recent past is any guide, though, the caseload could well decline this year.

In the last decade, the number of cases reported in Dutchess has largely fallen from a high in 2008 of 1,141 to a low of 386 in 2016. However, there have been spikes, such as in 2014 when 665 cases were reported and last year when there were 581.

Ulster County saw a smaller, but still dramatic spike in reported cases last year with 419, compared to 351 in 2016. Ulster also largely has seen a decline in the number of annual cases from a high of 778 in 2008 to the low in 2016. 

Statewide there was a 16 percent increase in Lyme cases from 7,543 in 2016 to 8,720 last year. 

Climate change, global travel key to tick diseases in New York, experts says

CDC toolkit provides info on Lyme, other tick-borne illnesses, highlights changes

.

Lyme, spread by the bite of blacklegged ticks, can cause fever, fatigue, a skin rash and occasionally more severe and lingering symptoms. It's the most prevalent tick-borne disease in the country and a particular problem in New York state.

Last year may not have brought the upstate Tickmageddon that some had predicted, but state researchers found plentiful ticks in the field last summer and fall — and more ticks equals more disease.

“We definitely had more cases than usual,” said Bryan Backenson, a research scientist with the state Department Health.

But why did the number of cases statewide jump from 7,500 in 2016 to more than 8,700 a year later?

Perhaps because it was an odd-numbered year.

An enduring curiosity of Empire State Lyme epidemiology is its boom-and-bust nature: For two decades, the number of cases has tended to jump markedly in one year, then decline the next year or two.

There were sizable year-over-year increases statewide in 2017, 2015, 2013 and 2011. Before that, the jumps came at slightly more irregular intervals.

The number of blacklegged ticks available to infect humans clearly varies from year to year.

It is influenced by a number of things, Backenson said, including winter weather, changes in the number of mice on which tick larvae feed and even the behavior of the physicians who diagnose the disease.

But there’s no clear reason for why the changes in caseload follows a seemingly regular pattern.

“I can’t explain … why it goes up in odd years and down in even years. It seems really consistent that way,” Backenson said. “Sometimes it doesn’t completely match that pattern, but in broad brush strokes it does seem to.”

Other trends in the Lyme caseload are easier to understand.

A doubling in the number of cases in 2008 compared to the year before, for example, was due to a change in federal rules that led physicians to report probable as well as confirmed cases.

As well, the geography of Lyme has changed over the years for seemingly logical reasons.

The disease was noted in Connecticut and on Long Island in the 1970s, and formally linked to a particular tick-borne bacteria, Borrelia burgdorferi ,in 1982. By the late 1980s, the case count was soaring on Long Island and in the Hudson Valley.

From there, the infection bacteria has spread to ticks in new parts of the state via the natural movements of mice and other animals that harbor the bacteria without being harmed by it. 

Lyme hit big in the Capital District, just north of the Hudson Valley region, in the early 2000's, data show. It began to blow up in the Southern Tier, just west of the Hudson Valley, in 2011.

The incidence of Lyme has been rising in the eastern Finger Lakes and Central New York, which border the high-caseload regions of the state.

"When I think about the leading edge... I think of a band between Syracuse and Rochester and down to the Pennsylvania border. That leading edge has been inexorably moving over the past 30 years to encompass more of the state," said Backenson, who is deputy director of the state Health Department’s bureau of communicable disease control.

There is no reason to think that high-risk line won't continue to move westward, he said.

"Will Rochester and Buffalo ever see the kind of case rate that we saw in Poughkeepsie, for example? I’m not entirely sure of that," Backenson said. "There may be something about the climate and habitat in the lower Hudson Valley that made that area have an explosion of cases.

"But will you see higher rates than you’re currently seeing? I think the likelihood of that is pretty high."