Tick Pictures

Avoiding Deer Ticks

Removing Ticks

Reducing Ticks

Disinformation

Politics of Deer Ticks

Tick Borne Diseases

BeSafeNewtown

Deer_Tick_Nymph

Dealing with Deer Ticks      


© 2002, 2003, 2006-2013 by John Moran, Newtown,CT, USA      
We can be absolutely certain only about things we do not understand." Eric Hoffer, "The True Believer"

Deer ticks are endemic in Connecticut so residents often endure deer tick bites. Frequently, this is cause for concern but a little knowledge about the deer tick can help to determine whether this concern is well founded. Less than 10% of bites can cause Lyme disease and it is possible to tell which bites are potentially dangerous with a 10x magnifier. Read on to learn more about the deer tick. Click for tick pictures plus notes or click here for detailed pictures of deer and dog ticks.

The Deer Tick's Life Cycle

Deer tick eggs hatch in the spring or summer beginning in April. The larvae from these eggs are very small, about 0.7mm or 0.025 inch long. The larva, like all stages of the deer tick, are blind and parasitic: they feed on the blood of mammals, reptiles and birds. The larva (which has 6 legs) "quests" for its blood meal by climbing up a stalk of grass or brush, then awaits the passage nearby of a host animal; any animal which brushes against the larva's perch becomes a host. A deer tick larva can wait for its meal for up to about 5 months before it dies from starvation or dehydration. About 10% of larvae find a host, feed and drop off to molt. If the host was infected with Lyme disease, the tick becomes a carrier. The most common host for deer tick larvae in CT is a mouse but other larger hosts, though less common, are possible including all small animals: chipmunks, squirrels, rabbits, birds, dogs, cats, deer and humans.

The larva's molting process, which takes a month or more, results in a nymph. The deer tick nymph has 8 legs and is a bit over 1mm long; nymphs are sexless being neither male nor female. The nymph quests in a manner similar to the larva but tends to climb higher, preferring high grass and low brush since it prefers hosts larger than a mouse: rabbits, squirrels, dogs, cats, deer and humans. Again, a small fraction of nymphs find a host, feed and drop off to molt.

The nymph's molting process usually involves overwintering so the adult tick emerges in the spring, and quests for a host. The adults are male or female, a bit larger than a nymph (again with 8 legs), and generally climb higher - up to several feet high in brush - to quest for a large host, preferably a deer or bear. Again, a small fraction find a host. Mating occurs on the host so this is another low probability part of the tick's cycle since both a male and a female must infest the host simultaneously. Adult female ticks can remain attached for a considerable time, apparently to improve the chance of mating. Reportedly, the adults can remain on a host over the winter. Generally, after mating the female drops off the host, lays up to 3000 eggs, and dies thus completing the life cycle. In temperate climates the overall life cycle is generally 2 years in the wild. The CDC site had a nice graphic which depicted the deer tick's 2 year life cycle very clearly but it has disappeared; the CT info still has it as does the ALDF site.

A deer tick acquires the Lyme disease bacteria when it feeds on the blood of a small animal (usually a mouse) which has Lyme disease. Once infected, the deer tick retains the Lyme disease bacteria through subsequent molts. The dog tick (aka wood tick) can also get Lyme disease but the disease is not retained through the subsequent molt so dog tick bites do not generally cause Lyme disease. (Dog tick larvae and nymphs are very similar to deer tick larvae and nymphs, it takes a sharp eye to tell them apart; the palps and hypostome are the most obvious differences).

Lyme Disease vs the Deer Tick's Life Cycle

Knowing a bit about the deer tick's life cycle helps to understand which tick bites are likely to cause Lyme disease:

1. If a tick has 6 legs it is a larva and is unlikely to cause Lyme disease (this was from the CDC site on Lyme disease but has been removed along with much of the other useful info that was there in 2004). It is important to examine the tick after removal (see below) and count the legs to determine whether you are at serious risk from Lyme disease.

2. Most tick bites in warm months are from larva since only a small percentage of deer tick larvae find a host and advance to the subsequent (8 leg) stage(s). That is, there are 10 times more larvae than nymphs + adults.

3. Tick bites in cold weather are more likely to be from nymphs or adult ticks and thus are potentially more serious. Estimates of Lyme infection rates in deer tick nymphs and adults range up to 80% in some areas.

4. Ticks acquired in brushy areas are more likely to be nymphs or adults than those acquired on a lawn. Ticks are commonly found in border areas between lawn and woods.

5. There are about 10 times as many nymphs as adult ticks so the nymph is the most common source of Lyme disease in humans.


Avoiding Deer Tick Bites

Clearly, avoiding deer ticks is difficult in many areas of Connecticut. On the other hand, avoiding contact with brush especially in cooler weather will help limit exposure to ticks which are likely to carry Lyme disease. Deer ticks do not stalk their host. Rather, they move to a likely spot on brush or grass and quest, i.e. wait for a host to happen by and brush against them. Since ticks drop off a host and molt or lay eggs near the spot where they drop, and since ticks typically don't move more than a few feet on the ground (deer ticks are blind), ticks will be found along game trails or in other areas frequented by deer or other common hosts.

Deer frequent the border between forest and lawn, generally walking on the grass with the idea of ducking into the brush if alarmed, so this is an area with a high probability of harboring ticks. Deer also take the path of least resistance through fences and stonewalls so avoid brushing against vegetation near gateways and other openings. Observation of deer plus a little thought will allow you to make intelligent choices when moving through areas frequented by deer. This is easier said than done: I often see deer gazing longingly through the fence around my garden yet I've found attached ticks twice after working in that garden.

Small animals (mice, chipmunks, squirrels) frequent stonewalls so avoid sitting on stonewalls to rest. Rabbits, possums, woodchucks, raccoons and other common mammals and birds have less predictable habits and so are liable to disperse ticks more randomly. People are at risk from these randomly scattered ticks even when using normally "safe" mowed areas well away from the normal deer habitat.

When a questing tick acquires a host it does not immediately bite that host. Instead, it moves around on the host for up to 4 hours searching for a suitable site. Generally, this is a protected site with soft, perhaps damp, skin such as in the armpit or under a watchband or the strap of a sandal. Taking a shower immediately after a walk in the woods may remove ticks which are still looking for a site. Immediately placing clothes in a clothes drier with heat for 15 minutes will kill any ticks wandering on those clothes.

Ticks also can hitch a ride into your home on a pet, accidentally drop off, then acquire you as a host. Treating your pet with Frontline will kill ticks which bite the pet but hitchhiking ticks are not affected. We've had much better luck with tick collars for pets.

It is conceivable (but very unlikely) for a mated adult tick to drop off of your pet and lay eggs inside your home; conditions inside a typical home make it essentially impossible for these eggs to hatch. The tick dies after laying eggs; it looks shriveled, unlike an engorged tick which dies without laying eggs -- see picture near the end of my tick pictures page.

When engaging in outdoor activities, DEET on shoes, clothing, and exposed skin repels insects and ticks as well (ticks are arachnids). Permethrin insecticide is available at Dick's Sporting Goods and elsewhere (several brands, check label for permethrin). Permethrin dries on fabric and will kill ticks for up to 3 months. Permethrin is neutralized fairly quickly (and harmlessly) if it contacts the skin so apply it to the outside of clothing only. Spraying carpets and furniture is a good option if you have pets who may bring in ticks. Hunters often apply permethrin to the outside of their clothing once at the beginning of hunting season; ticks reportedly die if they crawl more than 8 inches on treated fabric. A Google search for "permethrin clothing" will provide more information on its characteristics. The US military uses permethrin on clothing and DEET on exposed skin to minimize tick and insect problems.

When You're the Tick's Host

A deer tick bite is not painful but generally will cause a persistent mild itch: when you scratch, look carefully since they are difficult to see. If you determine you have a deer tick, removal requires care but becomes easier with practice. Commercial tick removal tools are generally not useful because the deer tick is so small (especially the larva) that the tool cannot get a grip on it.

Everyone exposed to deer ticks develops their own technique for removal. My wife and I have been hosts so often that we keep a tick kit in a plastic box which contains:

1. Rubbing alcohol. Note: Using alcohol may prevent PCR testing of the tick for Lyme or other diseases.

2. A couple of paper towels and q-tips

3. An X-acto knife from the hobby shop with a #10 blade (rounded with a point, not acute) Only the very tip is used so you may dull the blade if desired.

4. Scotch tape

5. A 10x magnifier


We wash the area with alcohol thoroughly. Then stretch the skin taut, put the tip of the knife firmly against a point just below where the tick is attached and (using the side of the knife) flip the tick upwards gently; a magnifier may help to do this accurately. It frequently takes a couple of tries but the tick releases; sometimes it sticks to the knife, sometimes it just lays on the skin. Deer Tick Larva(The goal is to remove the tick and a "micro-divot" of skin containing the hypostome -- this "micro-divot" should be tiny and should not draw blood. This technique is applicable to small ticks, especially larvae and nymphs. This picture shows a larva with a "micro-divot" on its hypostome (hard to see in the picture, but it is there). Err on the side of caution.) We use a section of Scotch tape to pick the tick up for examination - without tape, the tick is almost always lost. Wash the area again with alcohol. Avoid touching a tick with bare fingers since the Lyme bacteria could be acquired from a mangled tick. Video of tick removal.

Examination with a 10x magnifier is sufficient to count the number of legs. Our microscope allows a detailed examination so we know that our tick removal method generally leaves the tick unharmed or only slightly damaged. The hypostome (see below) is almost always intact.

Some sources recommend removing deer ticks by pulling them out with tweezers; this works on dog ticks but is a challenge with deer ticks due to their small size. Deer Tick Larva in my legThis picture shows the tick larva above prior to removal from my leg and makes it clear why the often seen advice to "grasp the tick by its mouthparts" is easier said than done despite the artist's conception in the CT paper. Ticks have a holdfast organ (called a hypostome) which looks like an arrowhead with a number of barbs so pulling causes the barbs to dig in deeper. In addition, ticks produce a type of super glue to prevent their dislodgement (which is why removing a micro divot with the tick is helpful). Squeezing a tick forcefully enough to pull it out may cause the tick to inject its stomach contents into the wound, possibly including Lyme bacteria, so think carefully before adopting this approach. Further, if the hypostome is broken off it will cause intense itching over an extended period until you succeed in scratching the remains of the hypostome out of the wound.

If the tick which bit you has 8 legs then it has the potential to transmit Lyme disease - but the transmission of Lyme disease is not assured even if the tick carries the disease. If the tick you remove has 8 legs and is visibly engorged then the chance of disease transmission is increased. Having a tick tested for Lyme disease is an option which, if it carries Lyme, may allow treatment to begin earlier. However the test is not totally reliable so this is a somewhat expensive crap shoot. Having a larva tested for Lyme is almost certain to be a waste of time and money....

To retain a tick alive, place it in a test tube or other small container and plug the entrance with cotton moistened slightly with water. If you moisten the plug slightly from time to time then the tick may live for a month or more. It is unclear whether the tick will survive the alcohol treatment suggested above since we have not had good luck keeping removed ticks alive for more than a day. Ticks and a common pinTicks can be retained indefinitely in a vial of alcohol.

Ticks and a common pin along with forceps for scale are shown at right. The deer ticks shown are l-r: adult, nymph, and two larvae (mounted on a microscope slide. Compare to the theoretical removal method here - advice on removing ticks is easy to find but much of it seems to be from people who haven't actually removed a deer tick (note how their model has a two part body, unlike a tick). ) A video showing tweezers and poor technique. A video with workable methods for MDs and for us amateurs.



A Speculation About Socks

A number of sources suggest pulling socks over pants cuffs as a method of reducing tick bites. I was bitten by an adult deer tick under my cotton sock so I have serious reservations about the protective capabilities of common socks. My speculation is that the fibers in socks are sufficently similar to animal fur that ticks deal with these fibers easily. Using women's knee length nylon stockings over cotton socks and tucking pants into these nylons might provide some protection. Wearing rip stop nylon pants and tucking them into the nylon stockings would potentially help more since the fine weave of rip stop nylon should be impenetrable to ticks and is slippery enough that they are likely to fall or be brushed off. Apply permethrin to the nylon pants and stockings for better protection.




On Reducing the Deer Tick Population

Reducing the number of deer ticks requires reducing the probability of survival at one or more stages in a tick's complex life cycle. When the number of ticks drops low enough, the Lyme reservoir hosts have a low probability of becoming infected so the disease nearly disappears. Unfortunately, there is always a small reservoir somewhere so the number of ticks must be maintained at a low level or the disease problem will recur.

A crude mathematical model helps to understand the tick's life cycle and the vulnerabilities inherent in that cycle:

All of the assumptions above are pulled out of the air rather than based on field measurements. Still, the numbers make some sense based on what is seen in practice. As long as the number of adult ticks at the end of the cycle is greater than the number at the start then the tick population will increase. There is little that can be done to affect the hatch rate so effort must be directed to limiting their ability to find a host or somehow making that host inhospitable.

Deer ticks are blind and find a host by climbing up onto grass or brush and waiting for a host to brush against them. Each stage of tick is larger and climbs higher when selecting its questing perch, assuming a higher perch is available in the immediate area; they do not travel far in search of a higher perch and will settle for whatever is available nearby. This simple questing strategy generally works well for the larva and nymph stages since there are sufficient rodents to support this tick population most everywhere. Adult ticks, when engorged, are much larger than the earlier stages and are more likely to be noticed and removed by small animals; by questing from a higher perch the tick is effectively opting for a larger host where it is less likely to be noticed. The tendency to climb higher occurs on the host also - ticks are often found on an animal's head and neck in preference to other locations. None of this behavior is cast in stone, so some adult ticks find small hosts and some larvae find large hosts -- however, this questing strategy evolved over a long time span: the tick's survival and prevalence are testimony to its success.

The deer tick's questing strategy allows their species to survive and multiply when there are sufficient hosts available. Still, most ticks perish from dehydration before a host happens by -- that is why our model uses a 10% survival rate at each stage. Ticks are not fussy eaters, they accept the first host that happens to brush against them. When the normal host is not present then they accept alternate hosts. However, recall that the adult deer tick's questing strategy is to climb higher than earlier tick stages when selecting a perch; this means that many alternate hosts are too short to be acquired by the adult ticks that found a higher perch. In Connecticut the most common large host is the white tailed deer; 90% of adult deer ticks which find a host find a deer(last paragraph, pg 52), the other 10% find an alternate host. (Note: these are percentages for ticks that find a host, about 90% of adult deer ticks fail to find a host and perish.) The white tailed deer is the "dominant host" for the deer tick in Connecticut, meaning the tick's population will decline if the deer's population density is lower than needed to ensure sufficient adult ticks find a host.

When the deer population is below about 10 per square mile, the adult deer tick's probability of finding a host drops below that needed for them to survive with a stable population so their numbers decline -- their questing strategy is a liability in this situation. In the mathematical model above this would mean that instead of 10% of adults finding a host less than 5% would find a host. While the model is not accurate, the concept is correct and the exact percentages required in the real world are achieved at about this density of deer population. The rate of deer tick population decline is proportional to the percentage of adult ticks which find a host, of course. When deer were totally eliminated from an area, the deer tick population was about 4% of the original level after 3 years and unmeasurable after 4 years. Alternate hosts likely allowed a few ticks to survive or the tick population would have dropped more rapidly. The Mumford Cove experience shows that maintaining the deer density at about 10 per square mile reduced the incidence of Lyme disease by about 80% (graph, pg 4 copied below for reference).

Mumford Cove experiment

Things can get worse: the Lone Star Tick is similar in many ways to the deer tick and can carry Lyme and other diseases; unlike the deer tick, the Lone Star Tick actively pursues its host. That is, if a host is detected the tick moves toward the host to improve its chances of acquiring that host. This tick is slowly spreading in the US and is established in Connecticut along the coast. The density of hosts needed for this tick's survival is likely lower than needed by deer ticks because of its aggressive pursuit of hosts.

Methods of Reducing the Deer Tick Population

Natural biological control of ticks by reducing the population of small host mammals isn't practical using snakes, hawks, owls, or other predators. Deer tick larvae and nymphs prefer rodents (mice, chipmunks, squirrels) but will use other animals and birds. Unfortunately, when the small animal population drops their predators tend to move on or die out (kind of a Malthusian feedback effect); this occurs at a level which leaves sufficient rodent population to support the deer tick larvae and nymph population. Applying insecticide to mice (pg 2) via permethrin impregnated nesting material in order to kill ticks infesting the mice isn't sufficient to significantly reduce the tick population, i.e. testing by CT AES showed MaxForce doesn't reduce ticks appreciably. Nor are other chemical controls economically effective, although you need to read between the lines of this paper to see this because tick reduction rates aren't quantified. Some approaches with bait boxes are incredible -- uncontrolled use of antibiotics on mice is almost guaranteed to develop treatment resistant strains of tick borne diseases.

Biological control of ticks with parasitic wasps, fungi, and virus have been tried and found limited success only at very high tick concentrations.

Another approach is to apply pesticide to deer, killing ticks (and other pests) on the deer. There are some appealing features to this approach: deer are the dominant host for adult deer ticks in temperate climate -- without deer (or bears in a few areas) this tick's population would be minimal, probably limited to incidental ticks arriving on birds. And, adult ticks often over-winter attached to a deer, then drop off in the spring to lay eggs -- this gives a long window of opportunity for application of pesticide. Since only about one larva in 1000 will survive to infest a deer as an adult, killing adult deer ticks on their dominant host would seem to be attacking the deer tick at the most vulnerable point in its reproductive cycle. This approach was tried on Monhegan Island, Maine and failed; the ivermectin treated corn killed ticks on deer but also killed intestinal parasites which plagued the deer, making the deer healthier. With improved health, deer reproduced faster resulting in an increased deer population able to support more ticks via deer that didn't ingest pesticide. Following that, deer were eliminated on Monhegan Island in 1999-2000; by 2004, immature deer ticks were no longer found on rodents on the island.

The 4-poster device is another way of applying acaricide to deer but suffers from high initial cost, high maintenance cost, and high maintenance effort. It has some limitations that make it difficult to use in suburban sites: it must be placed at least 100 yards from any dwelling and access by children must be prevented. A unit treats deer on approximately 40 acres and must be accessible by vehicle for regular refilling of the bait holder as well as replentishing the acaricide. Each unit requires about $500/year for expendables plus the cost of labor involved. Using corn for bait rather than a salt lick seems much more expensive from a material and labor standpoint; there is no indication whether a salt lick was considered as an alternate bait. One problem mentioned is that deer in the northeast are larger and eat more corn than deer in Texas where the 4-poster was developed. In addition, when acorns are available deer may ignore the corn in 4-posters so acaricide is not applied. Large scale trials of the 4-poster in the northeast were conducted in 1999-2004 (or 1997-2002, I've found both cited); oddly, a search on the net has not found clearly stated results for these large scale trials although there are many mentions of the trials starting plus progress reports through 2002.

4-Poster Tick Reduction Graph A CDC publication shows the 4-poster experiment failed in CT -- the tick population was reduced to 35% after 5 years and the rate of further reduction at the end of the study was low. With a tick population stable at about 35% of the original, sufficient ticks remain to pose a serious disease problem. Compare these results to this exclusion experiment (pg 53) where the tick larva population dropped by 84-100%.

It is my speculation that in the long run acaricide based tick control will fail: if the experience with the boophilus tick in the southwestern US is any indicator, resistant ticks will emerge. As noted earlier, deer tick control will be required for the forseeable future so the control method adopted must remain viable for the forseeable future.

The only workable solution so far in the northeastern US has been reduction of the deer population density. Some areas in Connecticut have over 100 deer per square mile (average 21/sqmi), resulting in high numbers of deer ticks (as well as damage to forests, homeowner's shrubbery and motor vehicles). The deer tick appeared in large numbers when the density of the deer population rose to high levels. Reducing the deer density to more normal levels in the range of 8-20 deer per square mile makes the adult tick's chances of finding a host much lower. About 90% of adult deer ticks use deer as a host (see pg 52) -- when the density of deer is reduced, the probability of an adult tick finding a host and surviving to lay eggs is reduced. When the probability of finding a host at any stage in the tick's multi-host life cycle is sufficiently low, the tick's life cycle and need for three hosts causes its population to dwindle. The adult deer tick tends to climb higher than larvae and nymphs when selecting a perch for questing; when large hosts are not available the adult's perch selection strategy becomes a fatal flaw for a large fraction of adult ticks.

The state of Connecticut has the highest per capita rate of Lyme Disease in the US. In response, Connecticut has produced a fairly comprehensive and growing collection of excellent reports (referenced above) describing experiments aimed at reducing the incidence of Lyme. These reports are careful to avoid suggesting a major reduction in the deer population as a solution because it is unpopular with a vocal minority. It takes a bit of thought to interpret the bar chart for this experiment where deer were fenced out of an 18 acre plot and the density of deer ticks measured in the central area and within the area but close to the borders. Detailed analysis is open to some interpretation but the main point is that when deer are excluded from a large area the deer tick population drops dramatically. This report does not go on to analyze the results of the exclusion experiment but instead talks about cleaning up leaf litter and spraying pesticides on large areas, neither of which is practical for an 18 acre farm, a state forest, or a town park -- all found here in Newtown.

Reducing the density of deer in Connecticut through hunting as a way of controlling Lyme Disease is very unpopular with a vocal minority who ignore or deny the validity of the reports cited above and suggest acaricides as a solution. CT state publications show that about 12,000 deer are taken through hunting and 18,000 are killed by motor vehicles yearly. The population of deer in CT is estimated to be 80,000+; deer population can double in about 2 years so predation from hunters and motor vehicles is insufficient to control the deer population. Human deaths in deer-vehicle accidents in CT are on the order of 10+ per year; the cost of treating Lyme Disease coupled with the effects of deaths from deer-vehicle accidents as well as the cost of damaged vehicles and other property damage from deer has not reached the level where hunting is seen as a solution although it is under consideration in some towns where a particularly virulent strain of Lyme Disease is prevalent. Loss of plant diversity in forests coupled with loss of bird habitat is causing a shift in the northeast's bird population but songbirds lack a vocal lobbying group. Clearly, songbirds don't have a lobby who thinks banning deer hunting is more important than protecting endangered bird species. The Audubon Society advocates reducing the density of deer to control their impact on other species of animals as well as their serious impact on plant diversity in forests; Friends of Animals views Audubon Society's actions with a different slant.

In researching deer and their impact on the environment I was surprised to find that ticks and Lyme Disease are one of the less common reasons for reducing the deer density. Deer are prolific so their numbers generally increase 40% a year when measures are not taken to control their population. Deer are causing long term problems with plant diversity and natural renewal of forests. The deer population density needed to control ticks is similar to that needed to prevent deer from damaging the ecosystem in general.


On NOT Reducing the Deer Tick Population

The current situation in Connecticut and much of the northeastern US is that the deer population density is sufficient to ensure that deer ticks survive in large numbers. This is a giant experiment in which the result of allowing deer density to increase has already had several unintended consequences, as noted above.

Unfortunately, the long term ramifications of a large population of deer and consequently deer ticks hasn't been thought through. Some of the results are becoming clearer. In the beginning, Lyme disease was identified and considered a serious problem, treatable with antibiotics. Over the years additional common tick borne infections were identified: bartonella, babesiosis, erlichiosis were most common. Patients who happened to get multiple "co-infections" from a single tick bite were (and remain) difficult to diagnose and treat -- with considerable controversy in the medical profession on many aspects of treatment. More time passed and the number to tick borne illnesses increased to 12, further complicationg diagnosis and treatment. At least one disease, babesiosis, is a protozoan parasite (like malaria) so treatment needs different drugs than those used for bacterial infections.

The establishment of new types of tick borne infections seems to work as one might expect: a few cases are noted of a new disease in one locale (like Lyme, CT) and then additional cases pop up in an expanding area until the new disease is established throughout the region. It isn't a great leap of logic to surmise that a tick (or bird or other animal) with the new infection arrived in the area and the disease spread via the established tick vector/host setup.

New diseases introduced into and amenable with this established disease chain should be expected to spread similarly, i.e. more diseases should be expected over time unless this chain is disrupted. Fortunately, deer ticks don't currently vector rapidly fatal diseases. Other types of ticks do transmit diseases with moderate fatality rates, e.g. Rocky Mountain Spotted Fever can be vectored by the Lone Star Tick which is now found in CT. Unlike current deer tick borne illnesses, RMSF can be transmitted via the egg to the larvae so the tick itself can be the disease reservoir.

In other areas of the world, more severe tick borne illnesses are known, e.g. CCHF. So it is conceivable for the existing deer tick situation with a well established host/vector chain to become extremely serious fairly quickly. The CDC apparently assumes that RMSF or other serious disease can't be vectored by the deer tick - seems like a major gamble with public health to allow this vector/host chain to persist, since Mother Nature has come up with surprises before. Here's a CDC list of recently recognized pathogens; note that at least two are vectored by the deer tick.

Of Politics and Deer Density

Author's Disclaimer: I am neither pro-hunting nor anti-hunting. I am anti-deer tick to the extent that I will accept any workable method, including hunting, that reduces deer ticks and the infections they carry. When I began this paper I assumed mice were the key but as I came to understand the deer tick's life cycle it became obvious that the only workable way to reduce deer tick density would be to reduce deer density by any pragmatic means. I believe I understand the deer tick's life cycle reasonably well and that sufficient information concerning this is presented above so readers who get this far have a reasonably accurate understanding of the tick's life cycle.

As a fan of Richard Feynman and especially his "Cargo Cult Science" essay, I've investigated the deer tick problem as honestly as I know how and have tried to link to the most pertinent information I came across in my study.

There is considerable controversy with regard to how to reduce the number of deer ticks. Presently, this is divided into two camps -- anti-hunting and pro-hunting. Armed only with information about ticks and their life cycle I believe I can often judge when an argument being used is defective or misleading. This may be harsh but my view is that when an argument's foundation is based on erroneous information or erroneous interpretation of information then the remainder of the argument is moot. That is, when the basic facts are wrong the conclusion isn't supported. Even harsher, when I have found two clear attempts to mislead I assume it is propaganda and become much more critical of the remaining material.

In considering the anti-hunting and pro-hunting arguments I evaluated the material presented on the following sites (all concern CT), judging the veracity of information presented using my understanding of deer ticks and their life cycle:

I read "Managing Urban Deer in CT" and found it generally coincides with what I've learned by personal experiment plus reading technical papers on the net, some referenced above. Earlier papers by CT were careful to avoid proposing hunting as a way to reduce Lyme disease in CT but this paper uses the results of the Mumford Cove experience to show that reducing deer density reduces Lyme disease rate. One criticism is that they did not also measure the tick population density. However, other studies that attempt to measure the tick population produce peculiar results, implying that it is difficult to accurately chacterize. Another criticism is that CT changed the Lyme disease reporting mechanism in 2002, reducing the cases reported considerably but it is not stated whether the Mumford Cove graph was adjusted for this. Another quibble: the paper provides the number of Lyme disease cases reported but does not provide the per capita rate so one must presume the human population was stable for the duration.

The NAB site provided information that conflicts with my understanding of the deer tick's life cycle. I clicked "The Minority Report" tab and then opened the complete text of that report, where Page 6 concerns Lyme disease vs deer ticks. The first paragraph contains several deliberately misleading statements. For example: "And, there can be infectious ticks and Lyme disease present on your property even when you don't have deer!" Based on the exclusion experiment referenced earlier, this is true - ticks can be carried onto a property by alternate hosts even when deer are excluded. However, the experiment showed that areas farther from the fence had far fewer ticks so a reasonable interpretation would be that deer ticks wouldn't be present at all if deer were not allowed in the vicinity of the fence. Alternatively, an infected tick could arrive on a bird, drop off and make the statement technically correct. This report emphasizes (on pg 6) that mice carry Lyme disease and deer do not; this is not pertinent to solution of the disease transmission problem -- while deer are not a reservoir for Lyme disease but they are a reservoir for at least one tick borne illness, erlichiosis (HGE) so this emphasis is hairsplitting. The fact that adult ticks use deer as a host is admitted but there is no recognition of how this affects the deer tick's life cycle. The Minority Report emphasizes: "Killing deer does not control Lyme disease." Again this is true in the narrowest sense: it is reduction of the deer tick via reducing the dominant host that controls Lyme disease, not the method of reducing the dominant host. Overall, "The Minority Report" reads like it was prepared by a lawyer: a series of statements, each true in some narrow sense, designed to lead to the desired conclusion - much as in defending a client. This approach doesn't work so well on technical matters; blunt truth rather than style is needed when dealing with Mother Nature.

The NAB site also linked to an HSUS report citing testimony to the Massachusetts Fisheries and Wildlife Board. This paper opens with a declaration that the deer tick is a multi-host parasite so it can't be controlled by reducing one host. This conflicts directly with the results at Monhegan Island and indirectly with Mumford Cove (as judged by reduction in Lyme disease). Statements on the next page note that deer were reduced at Crane Beach, Ipswich by 83% (from 350 to 60) and the tick population was not reduced. Stating deer reduction as a percent is a classic technique for misleading the unwary: the Crane Beach site lists area as 1234 acres or 1.93 square miles. I calculate that with 350 deer they had 181 deer per square mile and with 60 deer they had reduced the density to 31 deer per square mile. The CT DEP suggests that deer be reduced to 8-10 per square mile in order to reduce the tick population. Stating population reduction in percent is a slick way of making that reduction seem large so it is an often used subterfuge which is effective when the reader can't easily determine the resulting deer density. Here again, two attempts to mislead makes this complete report suspect.

With two suspect reports cited, I judged the NAB site to not meet at least one criteria discussed in Cargo Cult Science, i.e. first, don't fool yourself - and I believe the NAB site and both reports noted here have fooled themselves, the open question being whether it is accidental or deliberate. A minor quibble with the NAB site is that the main page is a very biased editorial; fortunately, it is so obviously biased that it is humorous.

The FCMDMA site mainly uses reports by state and government agencies to point out Lyme disease, ecological effects, and deer/vehical accidents as problems associated with deer overpopulation. This information generally mirrors what I've found in researching the deer tick problem (although in my concern with deer ticks I neglected to consider the effect of deer on forests until recently). The main quibble with the site is that they include editorial opinions from newspapers, etc. which are clearly opinions rather than facts; this isn't done in a way where it is confusing to separate opinions from factual material. The FCMDMA now includes Newtown; the BeSafeNewtown site promotes direct action by residents.

Having reviewed the above sites, I concluded the NAB/HSUS info is less believable than the CT-DEP and FCMDMA material. Which leaves me with the question of whether I am suffering from True Believer Syndrome, unable to accept inferences from legitimate experiments. That is, having arrived at hunting as the only practical approach based on my understanding of ticks am I biased such that I now look for studies that reinforce this conclusion and reject all others?

I believe current political tactics are being used in scientific contexts now, leading to decision by concensus based on the louder argument rather than the better measurement. Further, some of the "scientific" papers I reviewed while investigating deer ticks seem to have an agenda and in some cases mention effects noted that would seem to need to be justified before the paper is published, yet the paper is published without further mention of the odd effect.

On Disinformation and Deer

Reducing deer population density as a means of reducing Lyme disease, deer damage to forests, and deer/vehicle accidents is gaining traction based on measured results from a number of experiments, as cited earlier. The main method of reducing the deer population density has been through hunting and sharpshooting. The anti-hunting forces haven't found an effective way of combatting the expanding pool of information which shows the results, as in Mumford Cove, to be effective. The normal way of rebutting a fact based attack is to cite reports detailing conflicting facts. This hasn't worked out well so the anti-hunting forces have been waging a disinformation campaign. My review of the NAB site above shows one facet of this.

Another facet of the disinformation campaign is waged via letters targeting the local newspaper where the errors/fabrications are often egregious but may mislead some people, i.e. those who have not studied deer ticks. The disinformation campaign seems to be based on a list of "talking points", borrowing from current practice of the major political parties. The HSUS report cited by NAB gathers many of these talking points into one document, a blueprint from which letter writers seem to select items. Below, I have extracted some samples of this disinformation from our local paper and added explanations and/or citations to sources that show why I believe them to be disingenuous; check the HSUS document and you'll find most of them included there.

HSUS Fact: Hunts that removed a high percentage of deer - even up to 83% --- still did not result in tick decline! The main reason is that the Lyme disease-causing tick (Ixodes scapularis) is carried by over 40 bird species and all mammals. Actually, mice are the primary host for immature ticks which are the most infectious to people. A recent study underscored that Lyme disease risk is correlated with the abundance of mice and chipmunks (immature tick hosts) and food resources for these hosts (acorns), not the abundance of deer (Ostfeld et al, 2006).

The 83% vs actual deer density sophistry was covered earlier.

The fact that mice are carriers of Lyme Disease and deer are not is often emphasized. While deer are not a reservoir for Lyme disease deer are a reservoir for erlichiosis so this carefully parsed distinction is lost on sufferers of tick borne illness. In fact, neither mice nor deer transmit Lyme Disease to humans -- deer ticks transmit Lyme Disease to humans. In Connecticut, both deer and mice are necessary enablers for the deer tick's survival but at different stages in the tick's life cycle as discussed earlier. The only viable method to control the deer tick population demonstrated to date is reducing the density of the deer population. This was demonstrated in a Connecticut experiment which showed a major decline in the number of ticks on an 18 acre parcel fenced to exclude deer. The power of the anti-hunting lobby is demonstrated in this report where, after briefly mentioning the exclusion experiment demonstrating that reducing the density of the deer population causes a precipitous decline in the deer tick population, the report suggests raking leaves and using chemicals to control ticks!!! This non-sequitur might be humorous if Lyme Disease were not a serious problem... The 2007 DEP brochure, Managing Urban Deer in CT, is much more courageous.

This HSUS "Fact" is a mix of items dealt with above in exploring the NAB site. What is new here is the Ostfeld reference; however, Ostfeld didn't investigate the effect on Lyme disease of reducing the deer population. His paper basically concludes that survival of larvae and nymphs improves when there are more small (rodent) hosts, as determined by the food supply for those hosts. This is not a surprising conclusion and is essentially similar to noting that the survival of adult ticks improves when there are more deer per square mile as Spielman did. The difference being that the tick's life cycle is affected at a different stage. Ostfeld investigates what might be called the "fine structure" of tick survival but doesn't address tick survival when the number of deer is reduced. Ostfeld (pg 1064) says "... once deer abundance exceeds a low threshold value, further increases in deer density have little if any effect on nymphal densities." I.e., Ostfeld's experimental results apply only when the deer density exceeds some threshold value and he has not explored what happens when the deer density is below this (unknown, low) threshold-- not what I inferred from the HSUS reference. Makes one wonder if the "low threshold" is 8-10 deer per square mile...

HSUS Fact:

Ticks also thwart deer reduction efforts by switching to other hosts or congregating at higher densities on the remaining deer. The bottom line is that hunting doesn't significantly reduce the tick population.

If it were possible to eliminate mice, it is difficult to determine whether the deer tick could survive using alternate hosts and it is also difficult to predict the effect on other species (hawks, owls, snakes, etc) from removal of a major source of their food. (One unintended consequence would likely be an increase in gypsy moths - white footed mice are a major predator of gypsy moth eggs.) On the other hand, the deer population was at very low levels in CT until relatively recently with no apparent adverse effect on other species and most studies indicate the opposite -- the rise in deer population density has adversely affected other animals and plants. The rise in the CT deer population correlates with the rise in the deer tick population as might be expected based on the information above on the deer tick's questing strategy and the result this strategy has of making deer the tick's dominant host.

Recall that deer ticks are blind so they acquire a host by climbing onto a perch and waiting until a host brushes against them -- they take the available first host; they don't seek out or switch hosts, they simply use whatever host arrives first. Nor do deer ticks "congregate" on a host; again, they use the first host to brush against them. With fewer hosts available, it makes sense that more ticks would acquire the remaining hosts in slightly larger numbers. Some ticks might find an alternate host, i.e. some animal other than a deer will brush against them but the adult tick's questing strategy (using a higher perch than earlier tick stages) greatly reduces its chance of finding a host when deer are not available. The majority of deer ticks die awaiting a host; reducing the number of deer below 8-10 per sq/mi further reduces the survival rate for adult ticks sufficiently that tick numbers dwindle.

The bottom line, that "hunting doesn't significantly reduce the tick population" may be true but only under certain conditions, specifically where hunting doesn't reduce the deer population density sufficiently to affect the deer tick's ability to acquire a host. The often quoted Monhegan Island experiment (search for Monhegan here ) that eliminated deer from that island reduced the deer tick density to unmeasurable after 4 years. This shows that a heavy handed approach does exactly what theory would predict and demonstrates that the HSUS "fact" is clearly wrong. The Mumford Cove experiment demonstrates that a more controlled approach works too.


HSUS Fact: The inter-related effects of herbivory by various mammals, acid rain, European earthworms, pollutants, and other factors all impact forest succession and plants species diversity. It is easy to point the finger at the visible culprit while the more complex, cumulative, yet less visible factors aren't even called on the carpet.

Someone anticipated this line of argument and fenced a deer exclusion area within an area of forest, so all the factors are the same (except deer) - the pictures tell the story in a way that inadvertently ridicules this HSUS "Fact". Our old favorite, Managing Urban Deer in CT has graphic pictures of an exclusion experiment on page 5; apparently, this part of the disinformation campaign has been noted so countering information is provided. A similar, more scholarly, study was done by McShea and Rappole.

Here is some similar disinformation from another writer:

Deer are a factor in the transmission of Lyme disease over longer distances, but the main carriers are (and always have been) meadow voles, a.k.a. field mice. You could totally exterminate deer and still have an undiminished amount of Lyme infection because deer are simply not the carriers most implicated in transmitting the disease to humans. The fact that the infectious ticks are called "deer ticks" merely reflects that scientists discovered them on deer sooner than on mice because they looked for them sooner on deer; it does not reflect their primary host.

This is simply the same "deer are not a major factor in Lyme Disease transmission" talking point noted above for its frequent emphasis by the anti-hunting faction. Here the writer goes well beyond the normal bounds and declares that Lyme Disease would be undiminished if deer could be eliminated. This is precisely opposite to reported results in numerous experiments, several of which are mentioned and identified here and is specifically contradicted by the familiar chart (on pg 4)for Mumford Cove. The CDC believes larger deer population causes a larger tick population, increasing disease transmission (note found near bottom of page): "Note: Deer are the hosts upon which the adult ticks feed and are indirectly part of the Babesia cycle as they influence the tick population. When deer populations increase, the tick population also increases, thus heightening the potential for transmission.".

A common "refutation" of the Monhegan Island and Mumford Cove experiments is that they use an island and a peninsula so deer density reduction there can't be generalized to what would happen in a larger area like the state of CT. This is precisely backwards from what we know from actual experience: there were very few deer and deer ticks were essentially unknown in CT for at least 100 years prior to the relatively recent increase in deer density (1870-1970). What we don't know is what will happen if we don't reduce the number of deer, although some unfortunate ramifications are becoming clearer as time goes on.

A writer to our Danbury paper cited Millburn Township, NJ as a compelling example of the failure of hunting to reduce deer/vehicle accidents, noting that accidents rose after 9 years of hunting. It's worth looking at this Millburn report pages 12 - 14; page 12 considers the results of deer reduction programs in two other small NJ towns which were very successful. On pages 13-14 they analyze why their results differ (accidents rose from 21 to 22). It's a judgement call whether their analysis is correct - it looks reasonable to me. It is interesting that for several years during Millburn's culling program no deer were removed; coupled with the employment of Strieter Lite reflectors (well known as ineffective) it's clear a local anti-hunting lobby is doing its best to prevent this program from being successful. Millburn's deer task force is apparently undeterred by their opposition according to their most recent annual review.


Tick Borne Diseases

There is a surfeit of Lyme disease information available on the net so this paper will present only an overview and a few bits of information gleaned from a local Lyme seminar I attended. This site has considerable info on Lyme Disease and ticks.

Lyme disease, or borreliosis, is the best known and most common bacterial disease spread by ticks but it is not the only one: ehrlichiosis and bartonella are becoming more common due to deer tick bites. In addition babesiosis, a protozoan infection, is also contracted from deer tick bites. There are presently 12 diseases known to be vectored by the deer tick - and this list continues to expand. It is possible, and becoming more common, for a single bite to cause a combination infection involving more than one of the above mentioned diseases. The symptoms of a combination infection are often more difficult to diagnose than infection with a single disease; delayed diagnosis can lead to a more serious infection. The best known of the serious infections is called "chronic Lyme disease" and is more widespread than is generally recognized. Variations of borrelia as well as other diseases are steadily added to the deer tick's list.

In 2002 I speculated that the established host/vector disease chain, if allowed to persist, would eventually begin to transmit a fatal disease. As of 2013, this may have become a reality with the Powassan virus and its derivative, the Deer Tick Virus (DTV).

Lyme disease is caused by a spirochete form bacteria which can extract proteins from blood serum, allowing it to evade detection by the immune system and in some cases penetrate the cell wall. The bacteria can stay dormant within a cell for an extended period and then emerge later, typically when the immune system is challenged by some other event or condition.

The Lyme bacteria is apparently sensitive to testosterone, leading to a severe reaction in males more frequently than in females and children. This severe reaction typically includes fever, chills, general malaise, and the well-known bullseye rash; an acute Lyme reaction causes the afflicted person to seek treatment which is successful because it is begun soon after infection. Women and children more frequently have a milder reaction which is not recognized as Lyme leading to a delay in treatment; thus, the majority of chronic Lyme sufferers are women and children.

A considerable amount of information on the treatment of tick borne diseases is available in the paper by Dr. Burrascano . Those who believe that Lyme Disease is always resolved easily with antibiotics should read the short article by Dr. Sherr.



Notes about Tick Pictures

Click here to see six tick pictures I took through a microscope Use the link at the end of this page for many more detailed tick pictures.

The top picture is a nymph whose left palp was lost when he was extracted.

The larva in the middle of the page was recently removed and was alive when this picture was taken; it was held on a piece of tape, which shows in the background. This larva is engorged from feeding so it is larger than normal. This larva has a piece of my skin stuck to its hypostome.

The chelicerae are the cutters which the tick uses to penetrate the skin, allowing insertion of the hypostome. The left and right chelicera can be extended and retracted independently. In addition, the end of the chelicera can be moved outward to cause the barbs to grip the edge of the wound so the tick can pull its hypostome in deeper. The chelicera is about one thousandth of an inch wide, much thinner than a human hair.

The hypostome is the holdfast organ which anchors the tick to the wound while it feeds. In this picture the chelicerae are visible partially extended over the hypostome. The chelicerae may be extended beyond the end of the hypostome.

The foot or claw is found on the end of each leg. The claw is used to grasp the fur or hair of an animal which rubs against the tick while it is questing. Each numbered division on the scale is about 0.001 inch.

The embedded larva is just beyond the tip of the pencil. This picture emphasizes how small a deer tick larva is and how difficult it is to see, particularly if you haven't seen one previously. This is the same engorged larva shown in the center of the page. Our removal method deals with these nicely -- anyone want to use fine tweezers to "grip the tick by its mouthparts"?

Click here for more and larger pictures of deer and dog ticks.


The Practical Science site has some pictures and information helpful in identifying ticks. This Kansas State information is outline text at the college level.

If you have question or comment on this paper, click here.

Last Modified: 25 August 2013 02:44 MST

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