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

Where I practice, the prevalence of Lyme disease is high and the use of medication to prevent Lyme disease after tick removal has been shown to be effective. Ideally, the tick should be positively identified as Ixodes scapularis (or I. pacificus on the west coast of North America), 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.

In areas of the country where Lyme disease rates are lower, prophylaxis (treatment to prevent the disease) will be less beneficial. However, in my experience, many people are ready to take the drug. Its cost is low and the side effects are usually mild (occasionally nausea or even vomiting).

It can be difficult to spot an Ixodes nymph tick. They are small, about the size of a poppy seed. Most often, the bites that lead to Lyme disease go undetected and the tick falls off after four to five days. A good prevention strategy is careful tick control after possible exposure (hiking or even gardening in areas with deer). Removing ticks within 24 hours is very effective, and since there is no drug, there are no drug side effects.

A new vaccine against Lyme disease is in clinical trials.

Dear Dr Roach: In a recent column on weight-bearing exercise for osteoporosis, you didn’t mention that Writer’s exercise is primarily on an elliptical machine, which doesn’t provide an impact. Please discuss weight-bearing exercises with and without impact in relation to osteoporosis. I understand that cycling, swimming, elliptical, etc. offer less benefit due to lack of impact.

SL

A review of all the published studies on the effect of exercise on bone strength found that any exercise was helpful. Surprisingly, the most effective exercise to help the hip in particular was weight-free weight training, while the spine improved better when a person used multiple types of exercises. The classic teaching that a greater impact is needed has not been confirmed in studies.

When giving exercise advice, I try to identify what a person enjoys doing because they are much more likely to continue doing exercises that they enjoy. Weight-bearing exercises like walking, dancing, and the elliptical machine are definitely beneficial. Strength training turned out to be the “best” exercise in this review, and therefore adding strength training is definitely beneficial. Even balance exercises like tai chi have been proven to reduce the risk of falling and improve balance.

Dr Roach regrets not being able to respond to individual letters, but will fit them into the column whenever possible. Readers can email their questions to [email protected]

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