Lyme disease is the most common vector transmitted disease in the United States, with 30,000 reported cases annually and actual infections estimated to be 300,000 a year (CDC). If you frequent this blog, then you probably spend a decent amount of time outdoors. While Lyme disease is typically confined to the Northeastern United States, it has been reported in all states. It may pay off to think of Lyme disease even if you’re not in an area that has high incidence of disease. Here, I will talk about prevention and initial management of tick bites and Lyme disease.
The Daily Tick Check
The life cycle of the Ixodes tick is interesting, but not terribly clinically important. What is important is that the culprit, Borellia burgdorferi, resides in the midgut of the tick and upon attachment to a host, must travel to the salivary glands.1 This journey takes 36 hours so if a tick has been attached <24 hours, transmission is unlikely and prophylaxis is not needed. Thus, it is important for at-risk individuals to do daily tick checks. Ticks tend to attach to intertriginous areas (armpits, knee pits), periauricular area, scalp, body and head hair. Sneaky places to also check for are the posterior scalp line, gluteal crease, and posterior scrotum. Pet owners should also check their pets every day.
Effective methods of prevention include avoidance of exposure, wearing long pants and socks to cover skin, and using DEET.
I found one! Now what?
The recommended method for tick removal is to grasp the tick with fine tipped tweezers and apply gentle outwards pressure. It is okay if you accidentally crush the tick; studies show no increased risk of Lyme disease transmission if the tick is crushed2. If no tweezers are available, fishing line has also been effective.3 Tie a simple knot around the base of the tick and the skin and slowly tighten the knot while pressing down on skin to separate the tick. Do not tighten too quickly as this can sever the mouth from the tick and leave it embedded.3 Do not attempt to burn the tick with matches or a cigarette, or the smother the tick with petroleum jelly, gasoline, or nail polish. Smothering them takes too long and may cause the tick to regurgitate into the wound, increasing risk of transmission.3
In terms of antibiotic prophylaxis, give only if all 4 following criteria are met:1
- The tick can be identified as Ixodes adult or nymph tick
- Attachment has been estimated to be >36hrs based on degree of engorgement
- Antibiotics can be initiated within 72 hours of tick removal
- Local rate of Ixodes tick infection is >20%
The recommended prophylactic dosage for children >8yo and non-pregnant adults is doxycycline 4mg/kg up to 200mg orally for 14 days. If the 4 criteria are not met, or if the patient is <8yo or pregnant, prophylaxis is not recommended and only observation is indicated.
So you suspect Lyme disease
There are 3 clinical stages of Lyme disease: early localized (aka erythema migrans), early disseminated, and late disseminated. Erythema migrans is the classic target shaped lesion that appears between 7-14 days after tick detachment and expands over several days. Several days. Rashes that appear within 48hrs of tick bite are more likely to be a tick bite hypersensitivity reaction. If unsure whether a rash is from tick bite hypersensitivity vs EM, mark the edges of the lesion and recheck in 1-2 days. Hypersensitivity will not expand whereas EM will. Also be aware of STARI (Southern-tick associated rash illness) which can mimic EM but will not respond to antibiotics as no known bacteria have been isolated.1
Early disseminated disease typically occurs between several days to a month after the initial targetoid lesion. Unilateral facial palsy (aka Bell’s palsy) is the most common manifestation but don’t forget about other mononeuropathies or Lyme carditis which causes an AV blockade.
Finally, late disseminated disease most commonly shows up as monoarthritis of the knee. It will typically resolve over weeks to months even without antibiotics. Lyme encephalomyelitis is extremely rare and you will not likely come across it unless you’re a neuro ID expert in Maine.
To confirm your suspicion of Lyme disease, you can order serologic testing for C6 peptide enzyme, whole cell sonicate, or run a Western blot for anti-spirochete IgM and IgG.1 Note that IgM and IgG Borellia antibodies may remain elevated for years, making it difficult to differentiate between new and old Lyme disease. Other diagnostic methods include culture, detecting B burgdorferi DNA, or visualizing spirochetes from a biopsy but these methods are cumbersome, expensive, and not recommended for routine use.
Treatment for early localized disease in adults is amoxicillin 500 mg TID or doxycycline 100mg BID x14 days. In children, doses are amoxicillin 50mg/kg/day (divided over 3 doses) or doxycycline 4mg/kg/day (over 2 doses) x14 days. Remember no doxycycline for kids <8yo or pregnant women.
- Lyme disease has been found in EVERY single state, not just Northeast – but NE covers about 96% of cases
- Ticks must be attached for >36 hours to transmit Lyme disease so daily tick checks are an effective way to prevent transmission
- Doxycyline prophylaxis is generally not indicated unless transmission is very likely: the tick can be identified, it has been attached for >36 hours, antibiotics can be initiated <72hrs after removal of tick, AND local tick infection rates are >20%.
- Diagnosis can be confirmed with serologic tests, but anti-Borellia IgM and IgGmay stay elevated for years after infection
- Treatment for early localized is doxycycline or amoxicillin per dosages above. Stages beyond that warrant ID consults.
- Remember: NO doxy for kids <8yo or pregnant women!
1. J. Forrester, J. Vakkalanka, C. Holstege, P. Mead. Lyme Disease: What the Wilderness Provider Needs to Know. Wilderness Environ Med, 26 (2015), pp. 555-564
2. J. Piesman, M.C. Dolan. Protection against Lyme disease spirochete transmission provided by prompt removal of nymphal Ixodes scapularis (Acari: ixodidae). J Med Entomol, 39 (2002), pp. 509–512
3. G. Ghirga, P. Ghirga. Effective tick removal with a fishing line knot. Wilderness Environ Med, 21 (2010), pp. 270–271