It is caught by people drinking unpurified water. This frequently occurs at day care centers, where the parasite may be passed by toddlers just being toilet trained or during diaper changing. Thorough hand-washing is the best defense against this form of transmittal. Improper waste water treatment or a faulty septic system connection contaminates household water supplies. Giardiasis and other intestinal illnesses may be passed from family member to family member and on to guests through groundwater contamination.
Giardiasis is caught in the wilderness, and is in fact becoming more widespread.
Several precautions limit your chances of contracting giardiasis while camping. Carry a safe water supply with you. If that is not possible take your water from near the center of a lake, not from near shore or from a stream. Although running water in a stream may look cleaner, it is actually more likely to be contaminated. Fill your container from as far under the water surface as possible.