If you visit an where malaria exists (great site, Linda & Larry) you will be disqualified as a blood donor for a period of time after returning home regardless of how short of a time you were in the area or whether any mosquitoes were present.

In case your doctor does decide to prescribe anti-malaria pills for you, the following is a tip that was passed on to our daughter by a doctor friend who had made many trips to West Africa: before leaving home, take a sharp knife and score a line around the hard shiny coating of the pill. This will allow the medication to be released into your system better when you do take it.