Giardia can cause diarrhea, stomach cramps, gas, and nausea. You may feel sick once and then get better. Or your symptoms may come and go for some time. Some children with giardiasis do not grow or gain weight normally. Sometimes giardiasis does not cause any symptoms.
After a person is exposed to the parasite, it usually takes 7 to 10 days for the infection to develop, but it can take from 3 to 25 days or longer. You can pass the infection to others during the entire time you are infected. You may be infected for months, even if you don't have symptoms.