Ticks That Spread Lyme Disease Down 50 Percent
The decrease is attributed to numerous episodes of lower humidity this summer. Still, experts warn that poppy seed-sized middle-stage ticks are still a threat and another wave of adult stage ticks are coming this fall.
For the first time in years, a dramatic decrease has been seen across Aquidneck Island for summer deer ticks, which transmit the debilitating and sometimes deadly Lyme Disease, but experts warn that humans are not out of the woods just yet.
Dr. Thomas N. Mather, Ph.D, University of Rhode Island Professor and Director at the Center for Vector-Borne Disease, said the hot, dry summer so far has resulted in a significant drop in the deer tick population throughout all of Rhode Island by more than 55 percent and across Aquidneck Island by about 50 percent, as evidenced by preliminary data collections and field observations from sites in Middletown, Newport and Portsmouth.
The sudden drop reverses an alarming trend tracked on Aquidneck Island between 2007-2010, where the population of the most dangerous deer tick, the nymphal or middle stage tick, had risen by 80-200 percent, with the greatest increases seen in Middletown, said Mather.
"The nymphal stage deer tick is by far the most deadly and, until this summer, in recent years we had seen the largest increases in the state on Aquidneck Island, particularly Middletown near Newport at the southern, eastern area," said Mather.
The nymphal or middle stage deer tick is considered to pose the greatest threat to humans. One in five carries the deadly pathogens that cause Lyme Disease and—because they are about the size of a poppy seed—they often go unnoticed after attaching themselves to their victim host, Mather explained.
For a deer tick to transmit Lyme Disease, it must stay attached to the person's skin for about two days, said Mather.
"Before 2007, there hadn't been that many deer ticks on Aquidneck Island sites," said Mather. "Since then, we'd been seeing them reach the same levels as other parts of the state rapidly, and that was what was so striking."
Few biologists and medical professionals would argue: More deer ticks mean a greater likelihood of people contracting the debilitating Lyme Disease.
Lyme disease was first identified in 1975, and since then the disease has continued to increase, both in the number of people afflicted and in the geographic distribution. National surveillance for Lyme disease began in 1982, when 491 cases were reported. In 2004, the latest year for which statistics are available, there were 19,804 human cases verified by the Centers for Disease Control and Prevention. More than 60,000 cases are reported each year in Europe, according to Tickencounter.org.
"More people are truly encountering these tiny poppy seed size deer ticks and contracting Lyme Disease," said Mather, who maintains URI's Tickencounter.org and provides community outreach to warn humans about deer ticks and to educate them on disease prevention. Recently, he set up a display and distributed informational brochures at Newport's Easton's Beach to educate families and children on get the word out. His website also demonstrates the harsh realities of the deadly disease, profiling the stories of pain and tragedy of patients, as well as the anguish of those who've lost loved ones to the disease.
URI scientists attribute the 2007-2010 deer tick population surge to an ecological process wherein Aquidneck Island nature habitats had transitioned to second growth forests, which encouraged a larger white tail deer population that provides more hosts and carriers for the deer tick to thrive. Deer themselves are not carriers of the disease, as the ticks aquire the pathogens from mainly rodents, Tickencounter notes.
URI biologists who are studying the state's deer ticks have a working hypothesis that attributes this summer's sudden drop in the deer tick count to the hotter and dryer than usual summer.
"Humidity affects these deer tick populations considerably," said Mather. "Low humidity episodes kill off some of them, and we've had a number of these episodes throughout the summer."
Many deer tick die when the humidity level drops below 85% for more than eight hours, he explained. "It's like holding their breath, almost. If it's more than eight hours, they're done. If it's less, they can recover."
It takes about two summer seasons for deer tick to become a threat to people, Mather explained. Larvae that are hatching and getting infected this summer from feeding off creatures like rodents will grow into the most dangerous nymphal stage deer tick by next summer.
Between now and then, another wave of deer ticks will show up in the coming months that will present a new threat to humans.
The fall season brings adult stage deer ticks that have not died off yet; One in two carry the pathogens that cause Lyme Disease, compared to 1-in-5 among the nymphal stage ticks. More would-be victims generally see these larger ticks sooner and remove them before the disease can be transmitted. Regardless of whether a person is bitten by a tiny poppy seed-size nymph or the larger adult tick, it takes about 2 days for the insect to transmit the disease-causing pathogens, noted Mather.
Hikers or outdoor enthusiasts are recommended to carry pointy tweezers to remove any ticks immediately, take precautions for preventing tick bites, and consult their doctor immedaietly for suspected deer tick bites.
For more information or to download the Tick Encounter program widget to help spread awareness about tick bites and Lyme Disease prevention tips, visit www.tickencounter.org.
Early symptoms may resemble a "summer flu" and include:
- Chills and fever.
- Muscle and joint pain.
- Swollen lymph nodes.
- A characteristic skin rash that resembles a red "bull's eye."
Prevention is key.
- T—TWEEZERS—Use pointy tweezers for
- I—INSPECT—Check your body for ticks
at least once a day.
- C—CLOTHING REPELLENT—Use repellents with permethrin on clothing,
- K—KILL THE CRITTERS—Spray the tick habitat around the perimeter
of your yard.