Posted on 18 February 2015.
These days most of us have relatives or friends struggling with Lyme Disease and its devastating impact. An infectious disease, Lyme is caused by at least three species of bacteria from the genus Borrelia, which dates back some 20 million years.
Lyme disease in the United States was identified in 1975 when a constellation of cases was discovered in Lyme and Old Lyme, Connecticut. By 1978 scientists determined that it is transmitted by infected ticks.
Ticks and Lyme Disease in Western Washington
Although Lyme disease is relatively widespread in the Northeast and increasingly in parts of the Midwest, it remains fairly uncommon in our region. However, ticks infected with Lyme disease do exist here in Western Washington, and locally transmitted cases of Lyme disease occur here.
According to Washington State Department of Health (WSDH) entomologist Liz Dykstra, who specializes in ticks, there are three main types of ticks in Western Washington: the American dog tick, the coastal squirrel tick, and the western blacklegged tick (also known as the deer tick), which is the primary carrier of Lyme disease in the west coastal region.
Centers for Disease Control distribution of western blacklegged tick
“People don’t realize we have ticks at all in Western Washington,” Dykstra said. “We suspected that Lyme disease was here, but it wasn’t until 2011 that funding became available to test for the Lyme disease parasite. It’s probably been here for quite a while.” Dykstra explained that the tick that carries Lyme disease in the Northeast and Midwest is a separate species from the western blacklegged tick and that there is yet another carrier tick in Europe.
Since testing began in our area four years ago, Lyme disease has been identified in ticks in the following counties: Mason, Pierce, Clallam, and one in King. Dykstra was not aware of ticks from Kitsap County having tested positive for Lyme. However, she pointed out that only a small sample of 37 ticks from Kitsap have been lab tested. She said some ticks from Bainbridge Island have been tested but none have turned up a positive result for Lyme—”yet.” She explained that given the limited testing there is no way to know for sure if the disease is present in a given community. Kitsap Public Health District spokesperson Karen Bevers corroborated Dykstra’s data.
Western blacklegged tick larva, nymph, adult male, adult female courtesy of the California Department of Health
Washington State Department of Health epidemiologist Melissa Kemperman said cases of Lyme disease in our state have gone up somewhat from the mid-2000s but not dramatically. Between 2010 and 2013 there were 15-19 confirmed/probable cases of Lyme disease, with most acquired out of state. She said it is hard to say if the number of cases is rising: “It is low, but there is some risk out there. This is something we’re very interested in and watching closely. People should be aware.”
The Tick Life Cycle and Complex Host/Vector Relationship
Although many people believe deer are the main vectors for Lyme disease, deer mice are the disease’s reservoir. “Deer mice are the cute little ones in your garage in the winter time. They also carry hantavirus,” said Dykstra. Larval western blacklegged ticks hatch from eggs and attach to deer mice, becoming infected. As they grow, they drop off, molt into nymphs and find a slightly larger host to feed on. In their final life stage, nymphs molt into adults and look for a large host to feed on, such as deer, dogs, cats, and people. Interestingly, the ticks, rodents, and deer are immune to Lyme disease. People and dogs get it. Dykstra said cats appear to be less susceptible to it, possibly in part because they are more fastidious about grooming.
I asked Dykstra how deer mice contract the disease in the first place. “We’re not sure how it originates in the population,” she said. “It could have been brought here. Ticks keep it alive and passing around.” She said that other rodents common around human habitats, including the house mouse, Norway (brown) rat, and black (roof) rat, do not carry the disease.
Western black legged tick courtesy of Alameda County Health Department
Western Blacklegged Tick Facts
- Adult bodies are slightly smaller than the diameter of a pencil eraser and have white lines on the lower half.
- In the nymph phase they are the size of a poppy seed.
- They form a “cement plug” that helps keep them in place under the host’s skin.
- They inject anticoagulates to thin the blood and facilitate feeding.
- It takes 24 to 36 hours for a carrier of Lyme disease to transmit the infection to its host.
- Prime tick habitat in our region is the forest/field edge zone and grassy areas.
- They thrive in temperatures in the 50s and 60s and moist conditions, making spring (and sometimes part of fall) their most active time of year.
- Dykstra said with our mild February this year, the ticks are hatching now, with their prime months March through June.
- They can attach to a host for days and become increasingly bloated with blood, making them easier to find and turning their brown bodies a grayish color.
- Extremely bloated ticks can reach the size of a jelly bean.
Preventative Measures Against Ticks
The Washington Department of Health recommends protective measures against western blacklegged ticks. When in tick territory,
- wear long pants and long sleeves;
- tuck pant legs into long socks;
- wear Deet on exposed skin;
- spray clothes with Pyrethrum (it kills ticks); and
- afterward check yourself and your dogs thoroughly, especially around the neck, ears, eyes, belly, and underarms.
Signs of Lyme Disease Infection
Lyme disease bull’s eye rash
A “bulls-eye” rash around the bite zone is characteristic of Lyme disease but does not always show up or is not always noticed. The incubation period of Lyme disease is 3-10 days, and a prompt antibiotic treatment is most effective. Dykstra said that a Lyme disease infection can show up as a red bump, along with flulike symptoms, within 2-3 weeks of a tick bite. Anyone concerned about Lyme disease exposure/symptoms should seek prompt medical intervention.
The Washington State Department of Health recommends tick removal with tweezers as close to the bite site as possible, pulling it straight out. Dykstra said the western blacklegged tick is notorious for breaking off at its mouth parts. She said Lyme disease cannot be transmitted through the remaining head, but it can lead to secondary infection, so the area should be cleaned thoroughly.
Transmission of Lyme Disease
Dykstra hesitantly likened the transmission of Lyme disease in our area to a lottery. “The prevalence is very low, but if you happen to be the one that got the tick that happened to have it. . . .”
She encouraged people who find ticks on themselves or on their dogs or cats to send the ticks in for lab testing. “We’re missing folks because of a lack of lab testing,” said Dykstra. Not all ticks submitted will be tested, however, depending on funding levels and the condition of the tick.
Here is a form to include with your sample. Dykstra emphasized that the more information provided about the location and circumstances regarding ticks the better.
Photo of rash courtesy of Chris Booth.