Some useful points from a BMJ summary of the NICE guidance (note that I’m keeping this brief, as I’m trying not to duplicate points I already have):
May appear as much as 3 months after the initial tick bite (previous figure I had was up to 1 month). Minimum is still apparently 3 days. Usual incubation period is between 1 and 4 weeks.
An ECM rash is considered diagnostic; just go ahead and treat without testing. Otherwise, the test is ELISA followed up by immunoblot if positive.
If symptoms are persistent and the ELISA was done within 4 weeks of symptom onset, recheck the ELISA 4 – 6 weeks later. If symptoms remain after twelve weeks, proceed to immunoblot even if ELISA was negative.
If the immunoblot is positive, that counts as a definite diagnosis. If it’s negative and symptoms are continuing, consider alternative diagnoses and also consider referral to specialist.
Recommended treatment periods are now 21 days in most cases (28 for arthritis or acrodermatitis chronica atrophicans, but that’s something I’d be unlikely to be treating without seeking advice; the main take-home point for me here is that ECM or non-specific presenting symptoms should be treated with 21 days). Doxycycline is first-line choice for either of those two presentations, Amoxicillin second-line. Third-line is Azithromycin, which has a slightly shorter duration requirement; 17 days.
For children over 12, the recommendation is still doxycycline. Ditto for 9 – 12-year-olds, but in that situation it’s unlicensed although accepted specialist practice.
(I’ll look doses up if needed rather than writing them all out.)
(Having read this article, I then went back and reread my previous notes on the subject for revision of the various signs of middle/late-stage disease, so think this counts as a full credit rather than half.)