Dr. Roach: When and for how long to treat a tick bite to prevent Lyme disease | To your good health


Dear Dr.. Roach • Two days ago, I was bitten by a tick, which shed blood. Yesterday I was only given two 100 mg doxycycline capsules to take with a meal and instructions to “continue to see any symptoms”. It does not seem sufficient to me. Last year, when I was bitten, I received a two week course of antibiotics. I am concerned that the pathogens will not be completely eradicated after just one dose. Is this treatment new? What is your opinion? – KO

Reply • Where I practice, the prevalence of Lyme disease is high, and the use of medications to prevent Lyme disease after tick removal has been shown to be effective. Ideally, the tick should be positively identified as Ixodes scapularis, the blacklegged tick that transmits Lyme disease. Only engorged pupal ticks transmit the disease. This usually requires that a tick be attached to a person for more than 36 hours.

When used within 72 hours of tick removal, 200 mg of doxycycline was approximately 90% effective in preventing Lyme disease. The longer treatment, which is used for an established infection, is usually not necessary when treatment is started at such an early stage. Unfortunately, breakthrough infections can occur, although the risk is very low, 0.4% of study subjects. Continued vigilance, as requested, is appropriate.


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