Prevention
  • There is no vaccine to prevent giardia in humans, nor any recommended chemoprophylaxis (3)
  • Practice good hygiene: wash hands after using the bathroom, before eating, and after changing a diaper. (13)
  • Avoid consuming contaminated water:  don’t swallow recreational water, and don’t drink untreated water (13)
  • If traveling overseas to a developing country, be very care of drinking the water, and of raw food.  Try to drink only bottled (purified) water, and wash (and peel) all uncooked food (13).
  • If you must drink untreated water, use either sand filtration (the best way of getting cysts out of water) or boiling the water (1,19). Sand filtration filters are readily available at many outdoors-goods stores.
  • Avoid fecal exposure during sexual activity (6)

 

source: http://giardiaclub.com/pur-hiker.html
Portable water filter for backpackers.