Black-legged Ticks

This marks the 20th anniversary of my column for the Pennsylvania Game News. The first appeared in January 1993 and concerned the Carolina wren. Thanks for reading!
—Marcia

Black-legged tick

Last January I walked along the Black Gum Trail. Since our son, Dave, constructed the trail halfway up Laurel Ridge, back in the 1990s, I had never been able to take the trail in winter. Usually, it was deep in ice and snow as was our north-facing hollow road. But on that mild day there was not a smidgeon of ice or snow on the trail or road.

I neither saw nor heard any creature despite the warm day. The long-promised sun was trying to shine through a matrix of puffy, white clouds drifting past patches of blue sky. At dawn it had been 34 degrees and breezy, and the thermometer had been slowly rising all morning.

Then, as I descended the trail, I glanced down at my pants and socks and pulled off seven adult black-legged ticks. I could hardly believe it. I had considered winter to be tick-free on our mountain. Usually, they spend their winters buried under leaf litter that should be covered with snow. But they are tough creatures, and as soon as it warms up they are out and about. At that time the adult females are not carrying Lyme disease because they had had their last blood feeding on white-tailed deer. Some even winter on the deer.

But, as Dr. Richard S. Ostfeld of the Cary Institute of Ecosystem Studies in Millbrook, New York says, don’t blame deer if you get Lyme disease. The immune system of deer kills the bacteria that cause the disease.

“We don’t know why,” Ostfeld says, “but the deer immune system clears the infection. When they get bit, they wipe out Lyme. Deer play a tremendous role in suppressing adult ticks from spreading the bacteria.” He also dislikes the name “deer tick” and prefers “black-legged tick.”

three deer in snowy woods

White-tailed deer in Plummer’s Hollow (photo by Dave Bonta)

After all, like any arachnid to which ticks are closely related, the nymphs and adult ticks have eight black legs. But the larvae only have six. The larvae hatch from the several hundred to a few thousand eggs each female adult tick lays in spring. She then dies. Both the larvae the first summer and the nymphs the second summer feed once on a mammal and prefer white-footed mice, although they will feed on other small mammals or birds if they can’t find a mouse.

And it is white-footed mice that are the real culprits. They can get the Lyme disease bacteria and pass it on to the ticks even though the bacteria don’t seem to sicken them. Because nymphs are so small, no larger than a poppy seed, they are liable to bite and never be detected during the three to four days they need to take their blood meal. At least 70% of Lyme disease cases are from those nymphs that do not look like the black and reddish-brown adult female ticks. Instead, they have dark heads and bodies that appear to be translucent. Adult male ticks, which don’t feed but will attach to a host when searching for a female to mate with in the fall, are either black or dark brown.

Entomologist Thomas Say named the black-legged tick — Ixodes scapularis — back in 1821. But the first known case of Lyme disease wasn’t identified until 1975 when several children in Lyme, Connecticut were diagnosed with juvenile rheumatoid arthritis. It turned out to be what later was named Lyme disease. In 1982 scientist Willy Burgdorfer isolated the bacterium causing the disease, and it was named in his honor Borrelia burgdorferi.

Scientists also thought that a new species of tick carried the disease and named it Ixodes dammini. It was only later in the 1990s that they realized the tick transmitting the disease had been around and named long ago. But they did recognize that the tick belonged to the family Ixodidae, the so-called hard ticks. They have a hardened plate called a scutum on their idiosoma region, which is a specialized part of a tick’s body that expands to hold its blood meal.

White-footed Deermouse (Peromyscus leucopus)

White-footed Deermouse (Peromyscus leucopus) by J. N. Stuart (Creative Commons BY-NC-ND license)

Like ticks everywhere, the nymphs and adults climb a shrub or blade of grass, hold out their forelimbs, and wait for a victim to brush past. They also lurk on fallen logs, tree trunks, or even on the ground, especially the nymphs which can’t climb as high as the adults. Since they arrived on our mountain, about six years ago, I no longer have the pleasure of sitting on my hot seat on the ground, my back against a tree, watching the life of the forest. They even reach me on our benches unless I pull my feet up on to them.

Ticks have a Haller’s organ on each foreleg with spiny indentation packed with sensors and nerves capable of picking up a breath of carbon dioxide, heat, sweat, or even vibrations from your footsteps. So no bird or mammal can escape their sudden lunge. As I’ve discovered, the small huckleberry shrubs on Laurel Ridge Trail and the grasses of First and Far fields, are ideal “questing” posts for ticks, as well as the underbrush in our forest off the trails where I rarely venture anymore.

Once a tick arrives on its host, it probes around for a soft, bloody site to attack, often in private crevices. Normally, you won’t feel a thing. As David George Haskell writes in The Forest Unseen, “I suspect they charm our nerve endings, taming the cobralike neurons with the hypnotic music of their feet.”

The tick presses its mouthparts into your flesh and saws an opening. Then they lower a barbed tube, called the hypostome, to draw out blood. Because it takes several days to get a full blood meal, it cements itself to your skin with a glue-like material called “attachment cement,” which is why a tick is so difficult to remove.

During the first 24 hours it is attached, it is harmless. But later, when it is full, it takes water from your blood into its gut and spits it back into you, which is when it can transmit Lyme disease or two other diseases — babesiosis and anaplasmosis. The parasite Theileria microti causes babesiosis and Anaplasma phagocytophiolum causes anaplasmosis. As many as 2 to 12% of Lyme disease patients will have anaplasmosis and 2 to 40% babesiosis. This complicates the diagnosis and treatment sometimes because the tick might transmit one or the other or both diseases and not Lyme to a patient. In rural New Jersey, for instance, the Center for Disease Control studied 100 black-legged ticks and discovered that 55 of them had at least one of the three pathogens.

Black-legged tick on human skin.

Black-legged tick by Jerry Kirkhart (CC BY license)

Both babesiosis and anaplasmosis have flu-like symptoms similar to those of Lyme disease but without the telltale bull’s-eye rash. Some folks don’t recognize or even have symptoms of babesiosis, yet they can pass it on to others through donated blood. So far, Pennsylvania seems to be almost free of those two diseases, but they are more prevalent in New York and New Jersey. Unfortunately, it is probably only a matter of time until these diseases increase in the commonwealth.

Last year was supposed to be especially high in Lyme disease cases. That was because in 2010 there was a bumper crop of acorns, followed by 2011 when there were practically none. Dr. Ostfeld, forest ecologist Dr. Charles D. Canham, and colleagues at the Cary Institute first worked out the connection between the amount of acorns and the population size of white-footed mice. In abundant acorn years mice numbers soar but they crash when the acorn crop fails. According to Ostfeld, that leaves a large number of infected ticks looking for hosts. Without the mice, they are after us instead.

At least one hunter friend of ours contracted Lyme disease last June. Although he did get the rash, he never saw the tick. I suspect it was a nymph that bit him. He also listed four places where he could have picked up the tick — turkey-hunting at our place, at a friend’s country property, and on his own country property, or his backyard at the edge of Altoona.

If Ostfeld’s research is right, his backyard was the most likely habitat. In a paper for Conservation Biology Ostfeld and other colleagues entitled “Effect of Forest Fragmentation on Lyme Disease Risk,” they wrote, “Our results suggest that efforts to reduce the risk of Lyme disease should be directed toward decreasing fragmentation of the deciduous forests of the northeastern United States into small patches… The creation of forest fragments of 1-2 hectares should especially be avoided, given that these patches are particularly prone to high densities of white-footed mice, low diversity of vertebrate hosts, and thus higher densities of infected nymphal black-legged ticks.” Given both the size of our forest and the diversity of vertebrate species, we should have less Lyme disease here.

Japanese Barberry berries

Berberis thunbergii – Japanese Barberry berries by Virens (CC BY-NC-ND license)

On the other hand, another study by Tom Worthley and other researchers at the University of Connecticut Forest in Storrs claims that eliminating the invasive Japanese barberry shrubs (Berberis thunbergii) will help control the spread of Lyme disease, anaplasmosis, and babesiosis because white-footed mice favor the barberry’s habitat.

“When we measure the presence of ticks carrying the Lyme spirochete we find 120 infected ticks where barberry is not contained, 40 ticks per acre where barberry is contained, and only 10 infected ticks where there is no barberry,” Worthley says.

Unfortunately, our neighbor’s old 100-acre property that we were able to purchase only after it was poorly logged, is filled with Japanese barberry and other invasives. It’s also moved into the edges of our fields and even into the edge of portions of our older forest. Eliminating all of these bushes will take many manpower hours. But our caretaker hopes to experiment with a few of his own ideas for removing them over the next several years.

In the meantime, I’ll continue to follow most of the suggestions for avoiding tick bites, including super vigilance of my clothes and body, even in winter, when I take my daily walks.

12 thoughts on “Black-legged Ticks

  1. Contrary to your stating that Pennsylvania does not yet have much of a problem with Lyme disease, it is one of the 13 states with the highest incidence! See http://www.cdc.gov/lyme/stats/chartstables/reportedcases_statelocality.html for stats from the CDC. Pennsylvania is a high-risk area.

    As for the contribution of deer to Lyme disease, the black-legged tick and, consequently Lyme disease, would largely disappear were it not for the deer. The tick requires a large mammal for the adult blood meal. Mating takes place on the deer while the female is feeding. Without this blood meal, the female could not reproduce. Following engorgement and mating, it drops to the ground and eventually lays hundreds of eggs. Monhegan Island, too far off the coast of Maine for deer to swim to, got rid of their Lyme disease problem by getting rid of the deer.

    In 2011, 96% of Lyme disease cases were reported from 13 states:
    • Connecticut
    • Delaware
    • Maine
    • Maryland
    • Massachusetts
    • Minnesota
    • New Hampshire
    • New Jersey
    • New York
    • Pennsylvania
    • Vermont
    • Virginia
    • Wisconsin

  2. Thanks for your comment, but I did not say Pennsylvania did not have a problem with Lyme disease. I said that we did not yet have a problem with babesiosis or anaplasmosis but that it was only a matter of time until we do. Of course, we have a problem with Lyme. That’s why I’m writing about it. My whole column was a complaint about this disease and ticks that we never had until fairly recently on our central PA mountaintop. But eastern PA has been plagued by them for years. Incidentally, a friend of mine from southcentral PA tells me they don’t have a problem in his area. Your information about deer and Lyme re Monhegan Island is interesting. I guess I was relying on information from the Cary Institute of Ecosystem Studies.

    • You are quite right that your comment was referring to babesiosis and Anaplasma, which I realized upon a careful rereading. Sorry about that.

      I was glad, if one can use such a word under the circumstances, that you mentioned how your times in the woods have been changed by the presence of ticks. Entire lifestyles of families including my own have been changed by the expansion of ticks and tickborne diseases but it is very seldom mentioned even at times that it should be. For example one sees discussions about day camps or hiking activities in state parks, etc. where nothing is said about the risk of tickborne infections even though those areas are known to be at high risk. Seems like a strange disconnect in the consciousness. I lament the carefree days when I could just plunge into the woods and sit, like you mention, against a tree, hike, or go berry picking.

      I always enjoy your posts. Great picture of you, by the way.

  3. This article has the most information about the ticks, that I have ever seen. Thank you so much for this. One of my sons had contracted Lyme disease while camping in the Adirondacks several years ago. A cousin of mine has had this disease for quite a few years and is still quite ill at times.

  4. Thanks, Anna. I discovered, after this column went to press at Game News, that I had contracted Lyme disease from a tick I pulled off in early November. I didn’t bother to get an antibiotic because I thought I had gotten it within 24 hours and that it was too late in the season to contract it. I was wrong on both counts and am now on a 28-day antibiotic treatment. I feel fine now, although initially my left thigh and then knee swelled up like a balloon. Anyway, my brother, who lives and hikes in southern N.J. contracted it years ago and it wasn’t caught in time. He’s been suffering the effects ever since.

    Re white-tailed deer and their possible carrying the disease–We had a huge overpopulation of them back in the 80s and early 90s and started a deer-hunting program that has been wildly successful, due to a core of dedicated hunters, because we were worried about the forest understory being browsed to death by the deer. Our deer herd is now quite small and we have Lyme. Back in the 80s and 90s we had no black-legged ticks and no Lyme disease. But we have plenty of white-footed mice. So, I guess I will agree with the folks at the Cary Institute that the mice are the culprits. Unfortunately, they are not as visible as deer. However, my husband keeps a mousetrap permanently set on our kitchen floor and at least a third of the time it has killed a white-footed mouse. Our guesthouse has a similar, permanent infestation of them–the joys of living in old farmhouses. If so many of them come into our houses, how many more must live outside.

    • I live in Nothern Pa and we have have other co infection than the one that was listed. Unfortunatly I have them.
      I also have not heard about the fact that deer rid ticks of Lyme. I would like to see evidence of that.

      • Studies find that deer do not transmit the Lyme disease bacteria to other ticks. Their role in the Lyme cycle is they they are the way the black-legged tick reproduces. Adult female ticks must have a large blood meal to produce eggs. Usually, this is provided by a large mammal, most often a deer. The male mates with the female while she is feeding. Eventually, she drops off and lays a large numbe of eggs on the ground. The larva that hatch are not infected. They become infected as larva or nymphs, the next stage of development, if the small animal they feed on is infected. The immature stages of ticks usually feed on small animals like mice, shrews, birds, lizards, etc. Certain species of these amimals may be infected with Lyme, if so, then pass it on to ticks that feed on them.

  5. Thanks for your clarification, Marcia. If you want anymore information on this, Casey, you should check the Cary Institiute of Ecosystem Studies papers online.

  6. Marcia, I am so sorry that you did become infected (again?) recently. May your treatments give help and hope to you.
    Would you know of a medical person who would know how to find out if I have Lyme disease? I live now northern Mississippi. And where can I find on the internet, symptoms of Lyme disease. Also, I was in contact with those ticks without realizing it, in the late 1960s and in the 1990s. Thanks for listening to me. Anna Mae Schroeder.

  7. Growing up in rural northeastern Indiana and southern Michigan, the only tick I ever saw was on a dog that wasn’t well taken care of. Through thirty plus years of being outdoors hunting and playing and not one member of my family saw or worried about such a thing as ticks. There were always rodents and small mammals around then, but deer were a rarity in the 60s and 70s and there were no turkeys. It is difficult not to blame it on the rise of the deer numbers as that is all that has changed. The very woods where I grew up have gone from no ticks on people to literally dozens on anyone who hasn’t sprayed DEET all over his shoes and socks and lower pants. Even then an occasional tick drops on one from branches or sprigs. In NW Florida from the 1980s-2000s, again, I found one tick on me. Now they are everywhere. We need more answers.

  8. I agree that the medical establishment and the scientific community still do not understand all there is to know about the rise of Lyme-disease ticks and how they live their life cycles. Since I wrote the above, I’ve had experiences living with ticks that leave me with more questions than answers. But as with any thing in the natural world, the causes are multiple and intertwined and cover a wide range of possibilities. For instance, I see adult ticks here in March and April, October and November, but none in the summer, including the so-called tiny young ones. Also, numbers fluctuate wildly from year to year. We have cut our deer numbers way down and yet we have had our highest numbers of ticks. Go figure!

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