There is plenty of info on line regarding doxy. It is thought to work (providing the necessary blood serum level is maintained - 100 mg/day) by preventing cell division of the parasite .. ie you get bitten .. and the bugs die off in the next fortnight without replicating. Claimed success rate is reasonably high.. .. .Tends to affect individuals differently. I and several colleagues have no problems with medium term use (the general recommendation seems to limit use to around 3-4 months at a time) ... the photosensitivity needs to be watched a little to minimise sunburn. Several mining colleagues in SEA have been on the stuff continuously for far longer than that with no obvious side effects.. .. .On the antibiotic side, doxy is one of the fall back bugkillers .... keep you safe from all sorts of things a chap might otherwise pick up apparently .......