To the best knowledge of Scientists working on ways to prevent Lyme Disease and related tick-borne illnesses from infecting us human animals, sustained cold weather at ground level(beneath snow and leaf litter cover) at 14 degrees or below as well as severely hot and dry weather with humidity at 40% or lower will kill ticks...........Unfortunately, in the lower 48 states, our colder regions rarely have prolonged low and single teen Winter temperatures at surface levels..............And even during a prolonged single digit cold snap, temperatures actually warm with snow cover as experienced in Maine this past Winter.............."Temperatures below the snow were pretty much a constant 30 degrees, well above the 14 degree threshold below which ticks start to die"................"Even in areas where ticks had no protection from leaves or snow, they were surviving at rates between 30 and 40 percent"...................And in our arid southwest and Rocky Mountain states, we have created tick breeding oases via our planting of lawns and exotic shrubbery which we keep moist consistantly through the year via our sprinkler system paradigms................In the east, white-footed mice, masked and short-tailed shrews and chipmunks harbor the tick borne spirochetes which the ticks extract into their bloodstream via biting these rodents...............In the West, it appears that the western gray squirrel is the chief infection-carrying rodent that ticks feed on..................The ticks get a blood meal from the mice, chipmunks, shrews and squirrels,,,,,,,,,,,While the lyme and other diseases does not harm the ticks, the ticks give us the disease upon biting us..............And even though pharmaceutical trials are beginning again to test a vaccine that might make us immune from Lyme(not certain about the other tick diseases), we are some 5 years away from knowing if the results of the test will prove positve..............In the meantime, when gardening, hiking or just playing on the grass in your yard, it is a must to immediately shower(scrub up and down, all over, with a wash cloth) upon coming into your house..........Disrobe in your garage, put the clothes you were wearing into the hot water cycle of your washing machine(cold water will not kill ticks)..........The tick nymphs are the size of a speck of pepper so your best post-outdoor hygiene regimine is a must to avoid the debilitating symptoms associated with Lyme et al.

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Dry Weather May Mean Less Lyme Disease

by Dave Mance III

July 23, 2018

1 Comments

Illustration by Adelaide Tyrol

Over the past few decades, black-legged tick populations have grown relentlessly throughout much of southern Vermont and New Hampshire, and farther north in the Connecticut and Champlain Valleys. These are the ticks that carry Lyme disease, and so what was once a novelty illness has become a rite of passage for many. It’s probably safe to say that by now everyone reading this knows someone who’s had the disease, if they haven’t had it themselves.

But some years are worse than others when it comes to Lyme disease infection rates, so the obvious question is: what causes this? Part of the answer involves the number of deer and small mammals around. There’s been elegant science done that establishes a neat connection between Lyme disease rates and good acorn years. The oaks produce a good crop, which causes a spike in the mouse and chipmunk populations the next year, and then a surge in human Lyme disease cases a year after that.

Weather also plays a role, but maybe not in the way you might think. Around here there’s a lot of speculation every winter that maybe the cold will knock back the ticks. Unfortunately, any hope placed in this idea is probably misplaced. Remember that deep cold we had in late December last year, when much of the region dipped well below zero at night and didn’t get above freezing for two weeks? During this cold snap researchers were studying tick mortality in Maine, and noted that temperatures below the snow were pretty much a constant 30 degrees, well above the 14 degree threshold below which ticks start to die. Even in areas where ticks had no protection from leaves or snow, they were surviving at rates between 30 and 40 percent.

Dry early summer weather, though, like the kind we’re having this year, does affect ticks, or at least the rate at which humans contract Lyme disease.

CHIPMUNKS, WHITE-FOOTED MICE AND SHREWS
CARRY THE LYME AND OTHER TICK BORNE DISEASES
IN THE EASTERN USA

white-footed mice account for about a quarter of infected ticks. Short-tailed shrews and masked shrews were responsible for a quarter each and chipmunks for as much as 13 percent. 

Masked Shrew(top left) and Short-Tailed Shrew(top right)

“Most tick species show reduced host seeking behavior when it's dry,” said James Burtis, a  postdoctoral associate at Cornell University who’s studying the subject. “Black-legged ticks are particularly sensitive to desiccation, likely in part due to their smaller size and their adaptation to moist forest environments.”

Ticks can seem supernaturally tough. Pinch one with all your strength between the fleshy parts of your fingers and nothing happens. Drop one in a glass of water and it’ll just sit on the bottom wriggling instead of drowning, waiting for you to toss the water outside so it can walk away. But its Achilles heel is desiccation – a fancy word for drying out. They need moisture, which is why you find them in the moist leaf litter at the edge of the yard and not in the drier, mown parts. Expose a tick nymph to air with 40 percent humidity and deprive it of moisture for 24 hours and it will likely die.

Western Gray Squirrel harbors lyme disease in our Western States

In early summer, the tiny nymphs – about the size of a poppy seed – have to climb up a stem of grass or brush and then just hang there waiting for you or something else warm blooded to brush into them so they can eat. The wind dries them out. The sun dries them out. As a result, in hot, dry years, they need to climb up and down the vegetation more often to rehydrate. There’s evidence they don’t climb as high, since the farther they get from the moist duff layer, the more exposed they are; this presumably would make them more likely to be stepped on than brushed into. They may also do more questing at night when there’s more moisture, which further limits human exposure.

Some of the ticks might be dying in the drought. “There is some evidence that ticks burn through their energy reserves when it is hot & dry, said Burtis, “but those are just preliminary data.” It’s best not to make too much of this, though. In one long-term study carried out at the Cary Institute for Ecosystem Studies, researchers noted that while they collected fewer tick nymphs by “flagging” (dragging corduroy cloth through the brush) in dry years, the tick counts on rodents they trapped didn’t show a big variation between wet and dry years, which seems to indicate that many of the tick nymphs are still getting their blood meal, it’s just coming from a mouse and not a human.

Presumably the drought won’t last all summer, and so the nymphs could yet resurface with a vengeance. But in the meantime, being able to take my 17-month-old daughter into the woods with my tick alarm on “alert” instead of “paranoid,” is a nice silver lining to the too-dry weather.

Dave Mance III is the editor of Northern Woodlands magazine.

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https://www.sciencedaily.com/releases/2007/11/071129183745.htm

Chipmunks And Shrews, Not Just Mice, Harbor Lyme Disease

Date:

December 6, 2007

Source:

University of Pennsylvania

Summary:

Biologist in the tick-infested woods of the Hudson Valley are 

challenging the widely held belief that mice are the main

 animal reservoir for Lyme disease in the US. Chipmunks

 and two shrew species, not just mice, are the four species

 that account for major outbreaks.

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https://academic.oup.com/jme/article-pdf/42/3/388/18211580/jmedent42-0388.pdf

PATHOGEN/HOST INTERACTION, TRANSMISSION:

 Western Gray Squirrel (Rodentia: Sciuridae): A Primary Reservoir Host of Borrelia burgdorferi in Californian Oak Woodlands? 

ROBERT S. LANE,1 JEOMHEE MUN, REBECCA J. EISEN, AND LARS EISEN Division of Insect Biology, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 9472