I realize this may be a difficult question but I'm hoping there is an expert here, or someone will post a link which will describe the difference between the symptoms of having giardia, crypto, and food poisoning.
Here's the situation. I was 12 and went camping overnight with a friend on an island in the middle of a river. We had ice in a cooler. For dinner I opened a can of food, ate half, left can in cooler. Outside temps were 75-78F, not extremeley hot. The next morning I ate the rest of the food. I don't think I cooked it since I didn't feel like building a fire. Ice was still in the cooler, larger than fist-size (more like foot size.)
We took our own water, did not have a filter. My friend did not get sick.
Within 24 hours I had nausea, a little vomiting the first day, plus explosive diarhea. The Big D continued steadily for 4 weeks. I missed 4 weeks of school because I spent most of my day in the bathroom. Unknown to me I should have been in the hospital. I was dehydrating (having lots of headaches, first sign of dehydration.) I was very tired the first 2 weeks, probably due to dehydration. First 2 weeks I only slept and got up to use the bathroom (about every hour).
After first 2 weeks Big D started to taper off.
Now first, I didn't think food poisoning took off within 24 hrs. I thought it needed at least 48 hrs to build up toxins to the point of making you sick. So now I'm thinking it was giardia or crypto.
Cryptosporidium and Giardia both take about two weeks to develop a full set of symptoms. Food poisoning, in the medically accepted sense, is caused by toxins that develop from bacteria in food. It can develop within minutes of eating but usually takes a few hours for symptoms to appear. I'm sure that what you experienced was not Cryptosporidium or Giardia. I suspect it was either food poisoning or something you picked up earlier finally developing while you were on the trip.
Loc: Alexandria, VA
The symptoms (to all) can be similar at first. Yours happen rather fast and may have been from something you did before the trip if you rule out food poisoning from the canned chow!
Just a quick hip shot here but it sounds like the symptoms my fellow instructors had when they contracted Giardia up in WA State. Check out the fact sheet from the CDC. You can also research other possibilities on the same site.