Watery diarrhea is a primary symptom of isosporiasis, along with abdominal pain, weight loss, loss of appetite, dehydration, and passing gas (flatulence).
Most cases of isosporiasis can be diagnosed using a stool sample. To do so, the stool is stained with a dye and examined under a microscope. Another way to diagnose isosporiasis is by endoscopy or colonoscopy. These procedures use thin, long cameras inserted down the throat or through the anus to examine the small (and large) intestine. Samples of intestinal tissue are collected and examined in a lab.