The Important Facts About Lyme Disease

I recently went on a camping trip with my daughter.  Her elementary school sponsors a three-day camping trip for the Fourth Graders each year, and the kids have a great time.  They take orienteering classes, have a campfire, catch frogs and crayfish, hike along the Appalachian Trail, and learn about nature, themselves and their classmates.  I should divulge that this was my first foray into the world of wilderness exploration and roughing-it, so I was quite nervous about camping for 3-days.  But I chose to be a chaperone for three reasons: a) I wanted to spend time with my daughter, b) her birthday was on the second day of the trip and chaperoning was the only way I could spend her birthday with her, and c) she was recently diagnosed asthmatic and I wanted to bring her nebulizer.

Now that I’ve come back, I can say that I will think twice before camping again.  Why, you may ask? Because of the ticks. They were out in force, and seemed to be on every blade of grass and every tree stump. We were forced to check ourselves and each other for the little creatures continuously.  It became common to say two people checking each other like apes grooming their young. I was so traumatized that I still find myself checking for ticks. 

I learned a lot about nature and even more about ticks during the camping trip, including the art of tick removal.  But I left with lots of questions.  Can you catch Lyme Disease from all kinds of ticks, or just specific ones? How long do the ticks have to be attached? Should I take my child to the pediatrician if I see a tick on them, even if I get it off quickly? So I did a little research and here’s what I found. 

What the research says:

Lyme Disease is caused by a bacterium, not the tick itselfThe specific name for the bacterium is Borrelia burgdorferi sensu lato, and there are different subtypes of this bacterium.  The subtype that is prevalent in the US, Borrelia burgdorferi sensu stricto, causes arthritis if not treated early [1]. However, the most important thing to remember is that it’s not the tick, but a bacterium that the tick may carry, that causes Lyme Disease.  And not all ticks carry that bacterium.

Your concern should be limited to deer ticks or western black-legged ticks.  Hard-shelled ticks are the only natural agents through which humans have been shown to become infected [3].  In the Northeastern and Midwestern United States, the tick responsible for the transmission of the Lyme Disease bacteria to humans is the deer tick; in the Western states, the western black-legged tick is the main agent of dissemination [3]. Because ticks most frequently acquire the bacterium “from infected rodents during their larval feeding” [3], ticks that don’t feed on infected rodents are unlikely to have the bacterium. Consequently, dog ticks and wood ticks are not considered carriers for the Lyme Disease bacteria. 

Not all deer or black-legged ticks carry the Lyme Disease bacterium.  The number of ticks carrying the bacterium varies with the age of the tick and location. Infection rates can be as low as 2% for tick larvae, and as high as 30-50% for adult ticks [1, 10] in Lyme-Disease-prevalent areas.  However, it’s important to note that Lyme Disease is typically limited to the Northeast and Midwest in America [11].  Because of variations in climate, elevation, and tick behavior, most cases of Lyme disease occur in southern New England (southeastern New York, New Jersey, eastern Pennsylvania, eastern Maryland and Delaware) and parts of Minnesota, Wisconsin and Michigan [11].  

Ticks must be attached at least 24 hours to transmit the bacteria to humans.  Researchers have found that ticks must be attached at least 24 hours, and typically between 48 and 72 hours, to transmit the bacteria [8-10].  A clinical study published by Nadelman et al. found that bites from ticks that “had been attached to subjects for an estimated 72 hours or longer” were more likely to result in symptoms of Lyme Disease than were bites from ticks had been feeding for less than 72 hours [8].  Similarly, in an animal study published by Piesman et al., researchers concluded the following: “when ticks fed for 24 h, only one of six hamsters and none of eight mice became infected. In contrast, ticks attached for 48 h transmitted infection to three of six hamsters and two of eight mice. Finally, ticks feeding to repletion (-72 h) transmitted infection to five of six hamsters and all eight mice tested” [9].  So ticks attached for less than 24 hours are very unlikely to transmit the Lyme Disease bacterium. 

Prompt removal of the tick is the key to avoiding Lyme Disease.  Because transmission of the Lyme Disease bacteria requires several hours, rapid removal of a feeding-tick is important.  Keep in mind that immature ticks are very small, typically the size of a poppy seed.  So you’ll need to be thorough and diligent when searching.

You may be wondering how to remove a feeding tick?  “An attached tick should be grasped with fine-tipped tweezers as close to the skin as possible and removed by gently pulling the tick straight out” [1].  Because the bacteria reside in the tick’s gut, great care should be taken to grasp the tick by the head, and not by the lower body so that the contents of the tick’s stomach aren’t forced into the patient. 

When should you be concerned?  There are a couple of times when you should seek medical assistance.  A study written by des Vignes et al. found that attached ticks that fed on a person until engorged were able to infect the person with the bacteria 94% of the time [10].  Engorged ticks have generally fed for a relatively long time, so odds are you’ve missed the less-than-24-hour window that is so important for tick removal.  So if you ever find an engorged tick on you or your loved one, you should remove it and seek medical attention.  Likewise, if you develop a skin lesion or rash within 3 to 30 days of a tick bite, you should seek medical attention.  A skin lesion or rash is the most common and earliest symptom of Borrelia infection [7]. If left untreated, more serious complications can occur, including arthritis [1] and central nervous system involvement [5].  So, it is advantageous to seek medical attention early if you experience either of these.

What does this all mean?

Ticks are scary, and the prospect of Lyme Disease is even scarier.  But there’s no need to fear the threat of Lyme Disease if you know the facts.  And the facts are that some ticks carry the bacteria responsible for Lyme Disease, but many don’t. In the event that a tick attaches to you, it has to be attached for a relatively long time to transmit the bacteria. Hence the fact that less than 5% of tick bites in Lyme-Disease-prone areas result in transmission of the Lyme Disease bacteria [10].  So wear long sleeves, tuck your long pants into long socks, do a tick-check every night, and rest assured that you know everything you need to know to avoid Lyme Disease.

References:

1.   Lyme disease. Murray TS, Shapiro ED. Clin Lab Med. 2010 Mar;30(1):311-28.

2.   Updates on Borrelia burgdorferi sensu lato complex with respect to public health. Rudenko N, Golovchenko M, Grubhoffer L, Oliver JH Jr. Ticks Tick Borne Dis. 2011 Sep;2(3):123-8.

3.   Biology of infection with Borrelia burgdorferi. Tilly K, Rosa PA, Stewart PE. Infect Dis Clin North Am. 2008 Jun;22(2):217-34

4.   Lyme disease: the next decade. Stricker RB, Johnson L. Infect Drug Resist. 2011;4:1-9.

5.   Lyme disease: review. Biesiada G, Czepiel J, Leśniak MR, Garlicki A, Mach T. Arch Med Sci. 2012 Dec 20;8(6):978-82.

6.   Impact of climate trends on tick-borne pathogen transmission. Estrada-Peña A, Ayllón N, de la Fuente J. Front Physiol. 2012;3:64.

7.   Lyme disease--current state of knowledge. Nau R, Christen HJ, Eiffert H. Dtsch Arztebl Int. 2009 Jan;106(5):72-81;

8.   Prophylaxis with single-dose doxycycline for the prevention of Lyme disease after an Ixodes scapularis tick bite. Nadelman RB, Nowakowski J, Fish D, Falco RC, Freeman K, McKenna D, Welch P, Marcus R, Agüero-Rosenfeld ME, Dennis DT, Wormser GP; Tick Bite Study Group.  N Engl J Med. 2001 Jul 12;345(2):79-84.

9.   Duration of tick attachment and Borrelia burgdorferi transmission. Piesman J, Mather TN, Sinsky RJ, Spielman A. J Clin Microbiol. 1987 Mar;25(3):557-8.

10.                 Effect of tick removal on transmission of Borrelia burgdorferi and Ehrlichia phagocytophila by Ixodes scapularis nymphs. des Vignes F, Piesman J, Heffernan R, Schulze TL, Stafford KC 3rd, Fish D. J Infect Dis. 2001 Mar 1;183(5):773-8.

11.                 Human risk of infection with Borrelia burgdorferi, the Lyme disease agent, in eastern United States. Diuk-Wasser MA, Hoen AG, Cislo P, Brinkerhoff R, Hamer SA, Rowland M, Cortinas R, Vourc'h G, Melton F, Hickling GJ, Tsao JI, Bunikis J, Barbour AG, Kitron U, Piesman J, Fish D. Am J Trop Med Hyg. 2012 Feb;86(2):320-7

12.                 Temporal relation between Ixodes scapularis abundance and risk for Lyme disease associated with erythema migrans. Falco RC, McKenna DF, Daniels TJ, Nadelman RB, Nowakowski J, Fish D, Wormser GP. Am J Epidemiol. 1999 Apr 15;149(8):771-6.

13.                 Duration of tick bites in a Lyme disease-endemic area. Falco RC, Fish D, Piesman J. Am J Epidemiol. 1996 Jan 15;143(2):187-92.