Our next meeting is Saturday, March 28 from 1:30-3:30 with Doctor Waters, LLMD speaking. Think and perhaps write down any questions you have for Dr. Waters as there will be time for questions. Also, please bring back books you borrowed so others can have access to them as well.
With the warmer weather upon us, here is some excellent information on ticks. Remember, not all ticks go into a feeding diapause and can actively infect people all year round.
*Adult ticks lay their eggs in early spring and the larvae hatch about a month from when the temperature is warm enough.
*Transmission of Lyme spirochetes to eggs is low, although it does occur. When it does occur, viable spirochete levels in the eggs are generally 100%.
*Larval transmission in humans is rare, but it does occur.
*Peak larval activity is in August.
*As soon as larvae start to feed, they begin releasing a blend of chemicals into the blood stream of their host. These chemicals are cues for any spirochete already in the body to get to the site of attachment. Now they enter the previously uninfected tick and colonize the tick gut and pass to a new generation.
*Much like iron-filings and a magnet, the ticks have a special receptor (TROSPA) that binds to proteins (Osp, type A or OspA) in the outer surface of the spirochetes’s bodies, allowing gut colonization in the tick.
*From here, the spirochetes infect many other sites within the tick (hypodermis, central ganglion, salivary glands, ovaries, and connective tissues.)
*Larval tick drops off the animal after about 72 hours or 3 days. They absorb their blood meal and molt to change into a nymph, which takes about 35 days.
*The nymphs winter over and begin their activity the next spring. Many nymphs carry Lyme due to infection of the larval-stage tick. The number infected depends upon what kind of winter it was to the density of mice that year. Infection rates run anywhere from 3% – 100%. In endemic areas at least half of all nymphs are infected with Lyme at the beginning of the season, but more are infected as the season progresses due to the spirochete’s responsiveness to tick saliva factors during multiple nymph attachments.
*Nymphs begin activity in May and are very active all summer, and are highly infective. The overlap in the tick cycle ensures that most larvae will be infected before they molt.
*Nymphs feed 4-5 days, then they drop off and moult into adult ticks, which takes about 42 days.
*Adult ticks emerge from moult in Oct or early Nov and tend to not feed on anything smaller than a woodchuck or a dog and feed for 7-8 days. They then drop off and prepare to overwinter.
*Both fall-fed and spring-fed ticks lay their eggs (two to three thousand) in the spring, and then die.
*The eggs take about a month to hatch. There is high egg and larval mortality and both are fed upon greatly by predators.
*Ticks in warmer climates differ from ticks limited by colder temps. The warmer climates give the ticks life cycles that can run anywhere from 2-6 years. Unfed ticks can live up to 5 years without a meal.
*The primary reservoir for the spirochete changes from country to country and reduction of mice or deer results in a temporary reduction in ticks, but they rebound quickly, and the deer is not to blame as Madeira, a subtropical island, has no large mammals yet Lyme as spread prolifically due to two different species of rats.
*The use of pesticides to kill ticks also works for a while, but ticks have a tendency to develop resistance.
*Spirochetes are opportunistic parasitic organisms with experience in promulgating themselves. They infect a variety of biting insects.
*Nymphs feed quite happily on people, and this is where most human infections come from. Larvae feed on people too and while the rate of larva to human infection is low, the rate of human to larvae infection is much higher.
*Humans, along with birds, are one of the major life forms spreading the disease out of endemic areas.
*The Lyme spirochete takes advantage of the tick’s saliva. Studies have found that if levels of interleukin-2 and interferon gamma in lab mice are kept high, counteracting the tick saliva chemicals) the rate of infection drops precipitously.
“Most people think that bloodsuckers like mosquitoes and ticks disappear along with the risk for disease transmission once there is a frost and the weather turns cooler. That’s true for mosquitoes; they either die, or some species go into a feeding diapause. Some ticks also go into a feeding diapause in the autumn, but not deer ticks (Ixodes scapularis) – they are a different type of bug! The adult stage deer tick actually begins its feeding activity about the time of first frost (or early October throughout its range), and it will latch onto any larger host (cat to human) any day that the temperature is near or above freezing.”