Explosive. Diarrhea. Do I Have Your Attention?

Cyclospora. It's a quick way to lose weight, but not what I'd recommend.

I keep getting asked about the "explosive diarrhea" parasite that's been all over the news this week. Since I know a lot of you are living out of coolers and gas station food at shows right now, I wanted to break down what's actually going on.

  The parasite is called Cyclospora cayetanensis. It causes an illness called cyclosporiasis, and while we see a handful of cases every summer, 2026 is turning into a bigger outbreak year than normal. Cyclospora spreads through food or water contaminated with human feces, most often on fresh produce like herbs, leafy greens, and berries. It does not spread person to person, so sharing a trailer bathroom with a sick friend is not the risk. Sharing a salad or a water source might be.

As of early July, over 800 cases have been reported across 31 states, and none of those people had traveled internationally beforehand. That tells investigators the source is somewhere in our domestic food or water supply, though it has not been identified yet. Michigan has been hit the hardest, with more than 1,000 cases reported by the state.

  Here in Oregon, our numbers have stayed low so far, with about 7 cases in May and 7 in June according to the Oregon Health Authority. That is nowhere near what the Midwest is seeing, but I still want you to know the signs, especially with a summer of shows ahead of us.

  Symptoms usually show up one to two weeks after exposure. That delay is a big part of why the food source has been so hard to track down. Most people cannot remember what they ate two weeks ago, and I do not blame them. Watch for:

• Watery diarrhea that comes on fast and hits hard

• Loss of appetite

• Cramping, nausea, and fatigue

• Weight loss if symptoms drag on

If left untreated, this can last weeks to over a month, sometimes with symptoms that fade and come back.

Here is why I want my equestrian patients paying attention to this one specifically. Show season means eating on the go, sharing communal snacks and coolers at the barn, and pushing through GI symptoms because you have a class in twenty minutes and cannot afford to scratch. I get it. But watery diarrhea that will not quit is not something to just muscle through between runs. Dehydration on top of a hot arena and a full show schedule is a fast way to end up in real trouble, both for you and for your ride.

If you have had watery diarrhea for more than a few days, especially with fatigue or weight loss you cannot explain, call me. Diagnosing this requires a stool sample under the microscope with special staining, and because the parasite does not shed constantly, I sometimes need more than one sample to catch it. The good news is that it is treatable with antibiotics, and there is an alternative option if you have a sulfa allergy. Most people recover fully.

A few things to keep in mind at the barn and on the road this summer. Wash produce well, though washing alone will not fully eliminate the risk with this particular parasite. Stay ahead of hydration if symptoms hit, especially if you are also sweating through summer show conditions. And do not write off a stomach bug that is sticking around past a few days as just part of the grind.

  I will keep watching Oregon's numbers and update you if anything changes closer to home. If your gut is telling you something is off, literally, do not wait it out at the trailer. Come see me.