The "Watch Out for Parasites" thread started by ms. mathilda has pretty much run its course. However, I have just come across a Travel Health Advisory on gastrointestinal illness when traveling published by the Canadian Government that merits consideration. It is too long to repeat so here is the link:
http://www.hc-sc.gc.ca/pphb-dgspsp/tmp-pmv/2001/gastro_e.html
http://www.hc-sc.gc.ca/pphb-dgspsp/tmp-pmv/2001/gastro_e.html