Tick season chomping at the bit
In California ticks are ready to bite year-round, but there are peak periods for some ticks in certain stages of their life cycle. Winter happens to be when the adult ticks that can cause Lyme disease are most active.
In 2019 in Sonoma and Marin counties, about 1.1 percent of adult ticks and 5 percent of nymphs tested were infected with Borrrelia burgdorferi, the causative agent of Lyme disease, said Nizza Sequeira, spokesperson for Marin-Sonoma Mosquito and Vector Control District.
In addition to backyards, Sonoma Valley has thousands of acres of open space where the little buggers live, and given that the lifecycle of some ticks may be up to three years, ample time for one to latch onto a bare human leg or a dog shoulder passing by.
Called “questing,” ticks perch on the tip of blades of grass or the rim of leaves with their two front legs stretched out, and wait for a “host” to attach to, which then becomes a meal provider. They cannot fly or jump so they climb onto passing hosts that brush by.
Nymph or immature ticks are often found in leaf litter or logs, and adult ticks frequent tall grasses.
The three most commonly-encountered ticks in Sonoma Valley are the western black-legged tick – also called deer tick (Ixodes pacificus) – American dog tick (Dermacenter variabilis), and Pacific Coast tick (Dermacenter occidentalis), according to vector control.
Deer ticks are active October through July, with adult activity peaking in the winter and nymphs peaking in the spring.
“The nymphal stage of this tick is tiny and hard to detect on your body,” Sequeira said. “Both the adult and the nymph can transmit Lyme disease.”
American dog ticks are found November through June, and the Pacific Coast tick can be found from May through August, Sequeira said.
There are “hard” and “soft” ticks, each with a different life cycle. Hard ticks, such as the deer tick, emerge from eggs as larvae with six legs and seek a host for its first blood meal. After it feeds it molts into the nymphal stage and acquires eight legs and again seeks a host, feeds and molts again into the adult stage. This final stage requires another blood meal after which adult females drop off and lay a batch of thousands of eggs. Then she dies.
The length of time a hard tick feeds varies from several days to weeks depending on life stage, host type and species of tick. When the tick is engorged, the exterior surface of an adult tick can expand anywhere from 200 to 600 times its unfed body weight, according to UC Davis Department of Entomology and Nematology.
Some ticks, such as the deer tick, go through higher levels of activity during seasonal and life stages. For example, winter and early spring is when adult deer ticks are most active. Just about the time adult activity tapers off, nymphal ticks ramp up. Nymphal ticks – the immature stage when ticks pose a higher risk of transmitting diseases such as Lyme disease – are at their most active in the spring and early summer, according to the California Department of Public Health.
There are other diseases transmitted by ticks, such as Rocky Mountain spotted fever. Nymphs are responsible for most of human infection of Lyme disease, in part because they are so small and difficult to see and remove, according to the CDC. A tick must be attached to its host for 36 to 48 hours before the disease’s bacterium can be transmitted.
Ticks may take anywhere from 10 minutes to two hours preparing to bite. It feeds by grabbing skin, cutting in and then inserting its barbed feeding tube, which it uses like a straw to suck up blood. Some species secrete a cement-like substance that helps them stay attached.
Found on the west coast, the Western fence lizard has a protein in its blood that can kill the spirochete (a spiral-shaped bacteria) – which can cause Lyme disease and other diseases – in the gut of an infected nymph tick if the tick eats a blood meal from the lizard. When the nymph becomes an adult it will not pass on the bacteria.
The Centers for Disease Control (CDC) reported that in 2018 there was a total of 33,666 cases of Lyme disease reported nationwide; 23,558 confirmed and 10,108 probable. In California there were 62 confirmed cases of Lyme disease reported in 2018.
Contrast that to Pennsylvania, which reported 7,920 confirmed cases, and Oklahoma, which reported none. That doesn’t necessarily mean Oklahoma had zero cases of Lyme disease, it just means none were reported to the CDC.
The Marin-Sonoma Mosquito and Vector Control District doesn’t spray for ticks as it does for mosquitoes, instead it concentrates on awareness and prevention as the best route to take to avoid tick bites, experts said.
Kelly Liebman, scientific programs manager for the district, said they use a flag – a 1-meter square white flannel material attached to a pole – and drag it on the grass along trails in all Sonoma and Marin parks to collect ticks.
The ticks are brought back to a lab, separated into life stages and gender, and tested for Lyme and other diseases. The surveillance is conducted yearly primarily for awareness and education, Liebman said.
“We do not control ticks. Our focus is on education and surveillance,” Sequeira said. “We have a robust outreach program that includes giving presentations about ticks and tick-bite prevention to wide range of community groups”
The vector control district also provides free classes on ticks, mosquitoes and yellow jackets to all grades in local schools, which is so popular there is a waiting list, Sequeria said.
“The lessons focus on safety tips as well as the biology and ecology of ticks,” she said. “Each class borrows a life cycle kit that includes preserved tick specimens, magnifiers, and a tick life cycle wheel. Students are also provided with activity books that reinforce what was learned during the lesson.”
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