A Treatise on Ticks
8/1/2002
Basher_boy D.V.M.
Part of my job requires me to help people understand ticks and how they affect peopleâs health. I would normally not respond to a forum posting in such detail, but I think that it is important for geocachers to be well informed about ticks, so I am going to step up onto my lecture box. I hope no one takes offence. If any one would like to ask me any questions I would be happy to answer them.
Having spent several weeks in school learning to identify ticks and the diseases that they carry, I just wanted to clarify a common misconception about ticks. I read in this, and in other threads, that the Lyme disease tick is the size of a pin head, while the Rocky Mountain Spotted Fever(RMSF) tick is much larger. I say Lyme disease tick, and RMSF Tick, because in actual fact several different types of ticks can transmit these diseases. The most common vector for Lyme disease is Ixodes scapularis (common name: Deer Tick or Blacklegged Tick), but it is generally believed that Lyme disease may be carried and transmitted by any of the ticks in the Genus of Ixodes. RMSF can also be transmitted by the Deer tick, as well as its more common carrier the Rocky mountain wood tick (Dermacentor andersoni). These two are by no means the only transmitters of RMSF. In the East the most common carriers of RMSF are the Deer tick and the Dog tick (Dermacentor varabilis). You can get RMSF if you have never left the east coast.
It is difficult to identify ticks by size or color, or shape. All ticks go through four life stages.
- Adults mate and lay eggs.
- Eggs hatch into larval stage ticks that are usually smaller then a pinhead. These larvae are often called “seed ticks,” and readily identifiable because they have three sets of legs (as opposed to the four sets of all adult arachnids). Larval ticks are so small even when engorged that they are easily overlooked – see picture.
- The larval ticks molt (grow) into nymphs after the first blood meal. These ticks regardless of species are all a little bigger then an pin head, and all have four sets of legs.
- The nymphs take a blood meal, detach and molt into the adult tick. Identified by the large size and a four sets of legs. Identification of species is fairly easy to trained personnel at the adult stage. To make identification of ticks by size even more difficult there is sexual dimorphism in ticks as with most arachnids. Males tend to be ½ to 2/3 the size of females.
I guess the best thing for people to do is prevent tick bites in the first place. Use the pyrethrins (like permethrin) on your clothes, and DEET on your skin. Be careful with DEET, as some people react to it. It also can dissolve certain plastics/rubber. I have had more then one watch made into a permanent fixture. The most important thing that you can do is check each other carefully after being exposed to a tick environment. This includes the hard to search areas, where there is hair and excess warmth (scalp, groin, underarms, belly-button, etc.). Ticks take several hours to begin attaching and even longer to complete the implantation. i.e. they tend to be easy to remove for the first 6 hours or so.
To remove ticks: I have read a bunch of ways to remove ticks. The key is to get them off without them expelling more digestive fluids then necessary, without leaving any of the mouth parts embedded at the site. Burning gets the tick out very quickly, but they can expel quite a bit in the process. Vaseline type removal techniques tend to work well on ticks that are not FULLY implanted. Ticks breath through microscopic holes in their body. The Vaseline essentially suffocates them given enough time. If they are fully implanted it is generally believed that they can get enough oxygen from the blood they are ingesting, and therefore this method may be less effective on FULLY implanted ticks. Twisting ticks out is not recommended, as it tends to break off mouthparts. The best method is to firmly pull the tick out in the same direction that it is implanted. Do this without squeezing the body. I use my fingers, but most people would be better off with tweezers. Obviously nymphs or larvae will surely require the use of fine tweezers due to their small size. I am also personally allergic to ticks, and whenever a tick embeds I get an itchy welt. This is not the same as the infamous bulls-eye which many posters have quite rightly mentioned may or may not be present after infection with Borelia burgdorfi (the causative agent of Lyme Disease).
It is wise to hold onto any ticks that have managed to implant themselves. By far the best way to do this is place the live tick between two pieces of clear sticky tape. There is no chance that it will escape from this, and they are easy to handle, when entombed in this manner. I see many people talk about destroying ticks by flushing them down the toilet. This is probably an ineffective way to kill most insects as, they may escape the sewage system and live to bother us another day. Anything put into water tends to keep some air around it in the form of bubbles, and for a tick (as well as many other insects) this may be enough air to live on for a short while. My preferred method of tick destruction is to grind them between two hard surfaces. In the field this translates to two small rocks. I say grind instead of squash, because non-engorged ticks are very difficult to squash effectively, while grinding is a sure fire way to destroy them. I have seen many a tick walk away from a squash even when there is a distinct cracking sound. Burning them after removal is the way my mother used to do it, but it requires more complex equipment. The tape method mentioned above is also very effective, because once trapped they will never free themselves.
Finally I wanted to comment on a statement about Frontline, that an earlier poster made. The poster said that they put Frontline on their pet, and they still saw ticks on their pet. Frontline does not keep ticks from hopping aboard your pets, but prevents them from embedding. Some ticks will bite and take on enough Frontline that they will pull out and die, but the vast majority will get a taste of a pet with Frontline, pull out in disgust, and look for greener pastures. I donât know about you but my pups sleep with me, and it is possible for the hitchhiker to decide that I am the greener pasture. Although veterinarians used to swear by Frontline, more and more they are changing their tune, and thinking that a permethrin-embedded flea and tick collar in addition to Frontline is your petâs best defense. The collar will help repel ticks, while the Frontline will prevent them from embedding 99.9% of the time (I say Frontline because there are other pour on type tick preventatives available at pet stores, which I do not know about). The collar can be removed and used only as needed. It must be worn for 48 hours prior to an outdoor excursion to be effective. Also, once the collar has been removed from the package the volatile permethrins will de-gas, and the collar will become less effective over time no matter what you do. Frontline needs to be applied correctly every 30 days to be effective against ticks. I often find that on day 31 ticks will start to embed in my pups. I personally donât use a collar, but check my dogs after a trip outside. It is easy with my short-light haired dogs, but for those of you with the long or dark haired variety it would probably behoove you to use both Frontline and a collar.
Correct application of Frontline, requires repetition every thirty days, with a large enough dose for your size pet, directly to the skin, without getting the pet wet for 24-48 hours. Some things to keep in mind–Fipronyl (the active ingredient in Frontline) is broken down in sunlight. Some dogs are so big that it is necessary to apply some of the dose between the shoulder blades, and some between the hips.
Fipronil is toxic in larger then therapeutic doses to rats, with many long term effects including carcinogenesis. The effects on humans are unknown, but it is wise to minimize contact with the compound. It is highly lipid soluble, which means that latex gloves would offer little or no protection against exposure, and any contact will quickly be absorbed through the skin. I donât want to scare anyone form using the compound, but we must all balance the benefit against the cost. It works by paralyzing the tick/flea, especially the stomach, and intestines of the tick/flea.
One final note: Probably the best collar for tick prevention is a collar Impregnated with Amitraz. Amatraz is a compound that has been shown to be very effective against all forms of arachnids. It a much more selective compound then the pyrethroids or fipronil. It is not terribly toxic to insects (like fleas) or vertebrates (like your kids). Unfortunately these collars a more expensive, and are only available from your friendly Veterinarian.
Basher_boy D.V.M.
While Permetrin is to be used on clothes beforehand, can it also be used as a spray-on insecticide after the fact? In other words, after you return from the hunt and before you get in you car, spray your clothes down with Permetrin?
First a little bit on Pyrethrin/pyrethroid/permethrins:
Pyrethrin is a compound that was first isolated from the chrysanthemum plant, and found to be an effective toxicant against most invertebrates (nematodes, arachnids, insects, etc.)
Pyrethroids are any of the compounds that are similar to, or in the same family as Pyrethin. Permethrin is one, as well as Fluvalinate, Deltramethrin, Cyfluthrin, and Bifenthrin are some others that are labeled for the control of ticks. These compounds are all more or less toxic to ticks, insects, and vertebrates. It is not wise to come in contact with any toxin, but in small concentrations most Vertebrates should be safe at the labeled dose. Pyrethrin is probably the least toxic to humans, dogs, and ticks.
As far as toxicity of Permethrin : Permethrin Information sheet    Permethrin MSDS – consider the source. It is widely known to veterinarians that even mild exposure to therapeutic doses of permethrin to cats can be fatal to them. There are permethrin pour-on applications (like TopSpot) available at Walmart. Even though they are labled exclusivly for dogs it is not uncommon for a cat to be presented in seizures and respiritoy arrest to a veterinarian, after the owner unwittingly used it on his/her cat. Again my best advice would be to use any of these compounds as sparingly as possible, but don’t be afraid to use them with common sense when the benefit may outweaigh the cost. Permethrins have been classified as a class C carcinogen (i.e. they have been shown to cause cancer in mammals, and although no studies have been done in humans they very possibly may also cause cancer in humans). Also, the LC50 is highest via the respiritory route, and in younger or smaller animals.
I would imagine the labeled dose/use of Permethrin as a clothing toxicant should prove to be maximally effective. i.e. being cognicent of the possible toxicity issues I would keep my exposure to the compound as minimal as possible.
Is there anyway of destroying Just the Tick populations?
No there are really no selective ways to destroy just ticks in the wild. The same compounds that are toxic to ticks are toxic to other vertebrates and invertebrates to varying degrees. The best way to minimize exposure to ticks is to minimize the habitat. For most ticks in the east this is brush, while in the grasslands of the west (Gulf Coast Tick, and Lone Star Tick) it is the long grass.
Is there a natural predator that eats the ticks?
Tickâs biggest natural predators are believed to be birds, I am not sure which ones or even if specific birds like ticks preferentially.
Is global warming to blame for all the crappy bugs up in the northern part of the United States?
Global warming is unlikely to be a factor in the spread of Ticks. Many of the most well publicized ticks are what are known as cold weather ticks. Dermacentor sp. like cold weather and the mating adults are most common during late fall early spring. Ixodes sp. are the same. These are the species most responsible for RMSF, and Lyme Disease.
Ixodes sp.
What purpose do ticks serve in the wild? Where in the ecosystem of the forest that we all learned about in middle school does the tick fit in?
Ticks are a valuable food source in the wild. As I mentioned earlier birds eat ticks quite happily. Think of the Cattle Egrets that you have seen on TV picking ticks off of Cape Buffalo in Africa (Aside: the notion that these Birds are actually picking the ticks off of the Buffalo has been recently contested, and it may be that they are also making wounds and eating the blood that seeps from it). In old time farmyards the number one way to keep tick populations down was chickens. We often have had Guinea Hens for the same purpose. You might also ask yourself what the purpose of mosquitoes and horseflies are. I have a feeling that they fill a niche that is far from fully understood, and the diseases that they are vectors for also play a valuable role in the ecosystem.
In Africa DDT was sprayed religiously in parts of Botswana. This was in an effort to destroy the Tsetse fly Glossina sp./Tryptosome sp. vector/infectious agent axis. DDT effectively eradicated the Tsetse from the area, and consequently the diseases caused by the Tryptosome sp. organism. What it also did was allow both native and domesticated animal populations to grow out of control, to the point that there was a moderate population crash in the area due to over-grazing. It did however make a trip to the area much more attractive to tourists. You never want to be bitten by a Tsetse fly. They will slice open a cotton shirt to get into your soft flesh. It makes a Tabanus sp. (horse fly, deer fly, buffalo fly) bites look like a walk in the park.
Do you have links to any good sites concerning Borelia burgdorfi that are from a microbiological stand point?
- Lyme biology – A super accurate B. burgdorfi site by a Veterinary parisitologist.
- CDC – A nice CDC document about Borrelia burgdorfi
- Tick borne disease in U.S. – A nice page about various tick borne diseases in the U.S. (I read one inaccuracy in this one. Tick season for the deer tick is the beginning and end of the summer. But the Mid summer is the time when most people are venturing outdoors and coming in contact with ticks. Remember adult deer ticks/black-legged ticks Ixodes scapularis are cold weather ticks. Remember that this field changes almost as fast electronics. I bet that you didnât realize that the world was such a dangerous place!
If you are really serious about B. burgdorfi you might want to get onto medline and search the scientific literature.
I have lived in an area where deer ticks are a fact of life, when I walk out of my door. I usually pick one or two off me on an average day during the spring, summer, and fall. I personally donât use any of the fore mentioned chemical treatments. I rely on the check method. When I was a kid the whole family used to sit around the T.V. checking each other.
I donât know about your personal experience with lyme disease, but mine went something like this. I was bitten by a tick, of unknown species, which I found embedded in a large sore welt on the back of my arm. I went to the family doctor, and he sent the tick in, as well as sending in SINGLE immuno-assay test to the local lab. I left the doctor to start a “just-in-case” oxytetracycline course for one month. Both the tick and the blood came back positive for Lyme. This does not mean that I had lyme disease. To definitively find if I had been infected with B. burgdorfi I would have to have had TWO of the same blood test taken one or two weeks apart. In practice this is never done, as it is just easier and possibly safer to prescribe a course of antibiotics based on tick exposure and clinical signs. My medical record says I have had lyme disease, when in actual fact there is no scientific proof of the fact. The important thing for people to take from this is that exposure does not equal infection does not equal disease. It is important to play it safe. I have since had two more courses of oxytetrecycline for possible exposures to this organism.
Light colored clothing or dark colored clothing? Does it make a difference?
I had to research this one. There is some anecdotal research that ticks are probably more attracted to dark colors. I did a search on the AGRICOLA database, and several studies have been done that studied the best ways to attract ticks for research purposes. Tick traps are dark in color, with pheromones, and CO2 generators.
Many outdoog sites suggest the use of light colored clothing as a way to facilitate the identification and removal of ticks.
Incidentally a paper described the ability of orally ingested B1 vitamins as a tick repellant.
If we use permethrins on our clothing, does that level of exposure present a threat to our cats?
As far as permethrin toxicosis in cats: It is really not so much a question of toxicosis or not, but rather a question of degree. So although I would not anticipate any problems with your cat and your sprayed clothing, I would not rub his/her face in the clothes, and would keep him from contacting permethrins however I am able. Especially if there is no reason for him/her to come in contact with it. I am sure the concentrations are much lower then what is traditionally lethal to cats.
The author of this article has indicated that his area of expertise is along the east coast, and is therefore unfamiliar with the Tick/Lyme/RMSF problem in Wisconsin. While all the other information still holds true there might be some that is false for Wisconsin based operations.