ugh, i've had giardiasis in high school before. it was during a backpacking trip, i got the drinking water mixed up with the river water and took a healthy gulp... but to be honest, the treatment was worse than the giardia. while i had the "runs" from the giardia, the antibiotics for treatment (furizolidone?) made my stomach hurt really, really badly. i also lost control of my bowels a few times... not a pleasant sickness to get.