Tick uptick in NYC: Data shows pathogen-prone parasites in more parks

Ticks are spreading into new sections of New York City, bringing diseases with them as they infest parks, Columbia University researchers say.

The findings come as part of Columbia’s NYC Ticks research project, which launched in 2017 with a focus on Staten Island — the most tick-infested of the five boroughs, due to a large deer population.

Professor Maria Diuk-Wasser, the lead investigator on the project, said that as Staten Island has gotten control of its deer and reduced its tick population, the parasites have turned up in other boroughs that were thought to be relatively tick-free. The trend is expected to continue as climate change causes milder winters, making the ticks a year-round menace.

Meanwhile, the deer population in the region will continue to prosper thanks to man-made development and the elimination of natural deer predators. Statistics show cases of tick-borne Lyme disease have steadily increased in the city in the last two decades.

“We're finding more and more,” Diuk-Wasser said. “The ticks continue to expand.”

Last year, 80% of Brooklyn and Queens parks had blacklegged ticks — a dramatic increase from 2022, when researchers found the eight-legged critters in only 40% of surveyed parks. Ticks were found in popular parks including Prospect Park and Forest Park, and Diuk-Wasser said her team has also found ticks in Bronx parks.

She said Alley Pond Park, the second-largest park in Queens, is one of the most infested in the borough.

The researchers conduct their tick census by dragging a white banner through wooded sections of parks. The ticks stick to the fabric and are plucked off with tweezers, put in tubes and tested for pathogens at a lab.

So far this year, about 70% of parks surveyed by the Diuk-Wasser's team have disease-carrying ticks.

Data from the city's health department shows that Lyme disease cases have also steadily risen. In 2000, there were 215 cases of Lyme disease in the city. In 2020, there were 704 cases. In 2023, there were 3,323 cases.

Lyme disease isn’t the only risk. City residents were also afflicted with other tick-borne illnesses. Last year, nearly 200 New Yorkers were diagnosed with anaplasmosis and babesiosis, which have severe flu-like symptoms.

Other tick-borne illnesses are also emerging, such as a red meat allergy known as Alpha-gal syndrome. Different types of ticks carry different pathogens. Diuk-Wasser’s team has found four varieties of ticks now in outer-borough parks and adjacent yards: blacklegged ticks, Asian longhorned ticks, Lone Star ticks and American Dog ticks.

“On Staten Island, all four tick varieties are present and a significant problem,” Diuk-Wasser said. “Most people are concerned for the blacklegged tick or the deer tick, which is a Lyme vector.”

The blacklegged tick carries a total of six pathogens.

Last year, the city's health department said ticks had been found in all boroughs and that the highest concentrations were in Staten Island and northern parts of the Bronx, including Pelham Bay and Hunter Island. The city downplayed the risk in other parts of the city.

“Most NYC residents diagnosed with a tick-borne disease are infected when visiting grassy, wooded areas in upstate New York, Long Island and surrounding states. However, several types of ticks have been found in New York City,” the health department states on its website.

In 2016, the city started a deer vasectomy program on Staten Island, which has reduced the population to just under 1,300 deer — a 41% drop. The decline in deer has corresponded with a decrease in blacklegged ticks on Staten Island. Research has found that deer are resistant to Lyme disease and serve as a primary host for female ticks, giving the mammals a critical role in the parasite’s life cycle.

“If you have deer in your yard, you have a high likelihood that there will be ticks there too,” Diuk-Wasser said.

In Staten Island, deer-control measures are correlating with decreased cases of Lyme disease. In 2021, the city's parks department reported a 21% decrease in the deer population due to the vasectomy program. That same year, Lyme cases dropped in Staten Island by 60%.

She guessed that birds might have brought ticks to other deer-free areas, such as Prospect Park. A spokesperson for the Prospect Park Alliance disputed the Columbia ecologist’s research, saying no ticks had been found in the park.

The parks department did not return a request for comment.

Ticks are mostly found in wooded areas, according to researchers.

“The blacklegged ticks will be present when there is forest and leaf litter, and especially when you go off-trail,” Diuk-Wasser said. “If it's a very manicured park, I would say you're relatively safe.”

The riskiest time of year is May through July, when the poppy seed-sized nymphs are out. They’re so small that they can be hard to spot during a post-hike tick check.

Still, experts cautioned that tick data is tricky because it’s difficult to confirm the origin of a tick bite. People travel during the warm months and usually don’t immediately notice when a tick has jumped on them for a ride.

The NYC Tick project hopes to better understand the rising tick-borne disease rates in New York City by collecting more data on travel history and activities of people who have been bitten.

Adult ticks are larger, about the size of an apple seed. They pose a year-round threat. As long as temperatures remain above 35 degrees, the arachnids can survive.

Climate change contributes to the rising likelihood of four-season transmission around the city. Warmer temperatures are also more favorable for the booming deer population.

“The climate would have two effects: making them [ticks] active year-round, and then the main effect is deer continue to grow,” said Diuk-Wasser.