
The documented chain, and the hypothesis this post is about.
Every time I raise irrigation water in this outbreak, the same sentence comes back at me. The water comes from deep wells. There is no Cyclospora in a well six hundred feet down. It is a good answer. It is also, on the government’s own record, an answer to a question nobody asked.
Open FDA’s environmental assessment of the Doctor Mora plant, published in November 2013 after cyclosporiasis sickened hundreds of people in Iowa and Nebraska. The report says all five assessed ranches use well water, and that the wells run roughly 650 to 1,000 feet deep with casing to the water table and cement surface seals. That is the sentence the industry quotes. Two sentences later comes the one it does not.
In 2013 three of the assessed ranches used elevated irrigation water holding ponds. Both lined and un-lined ponds were observed.
And the reason FDA gives is not a food safety reason at all. It is an electricity bill. Some of the wells lacked adequate flow rates for direct irrigation, and the power to run the well pumps was much cheaper at night than during the day. The growers therefore pumped after dark into open ponds and drew from the ponds when they needed to irrigate. At Ranch B the water from two wells was combined in a single elevated reservoir before use, and that reservoir was dosed with copper sulfate to keep the algae down. Nobody treats a sealed pipe for algae. Algae needs sunlight and open air, and if you are managing algae, you are managing an open body of surface water.
That is the whole of the deep-well defense, and it collapses on a definition rather than on a fact. Nobody has to argue that this parasite is swimming around in the Guanajuato aquifer. Water that leaves a six-hundred-foot well and then sits in an unlined pond under the sun is not well water anymore in any sense that matters to a parasitologist. The industry’s own rulebook says so. California’s leafy greens standards make growers categorize every source separately — well, reservoir, canal, municipal — and treat water from open sources such as a canal or reservoir when it is applied overhead in the twenty-one days before harvest. The distinction between a well and a pond is not something I invented for a blog post. It is a line the industry drew itself and then stopped mentioning.
Taylor Farms knew it too, and its own numbers are in the same federal report. In response to the 2013 outbreak the company ran its own assessment across the plant and thirty ranches and collected 793 samples. The categories are itemized: 81 well samples, and 48 from reservoir and storage. Six more reservoir and storage samples under environment. Three from a reservoir listed as no longer active. Ten from run-off and standing water. Eight from drain ditches. Seven from rivers, streams and canals. A company that sends technicians out to sample drain ditches and standing water is not a company that believes its irrigation water never touches the surface of the earth.
FDA did look at the ponds in 2013, and it is worth being precise about what the looking consisted of. The team walked the entire perimeter of each holding pond and found no indication of human or animal intrusion and noted that the ponds were fenced inside a fenced ranch under twenty-four-hour security. That is an intrusion check. It answers whether somebody climbed in. It does not address rain running off surrounding ground into an open pond, it does not address birds, and it does not address what an unlined pond exchanges with the soil water around it. The report’s one sentence about flooding is specific: the team found no indication of flooding or other potential irrigation water contamination at any of the wells. The wells. The ponds are not in that sentence.
So, what does 2026 look like? So far, silence.
Now the part where I am speculating.
The first half of 2026 was the wettest in Guanajuato in nearly a decade. The Servicio Meteorológico Nacional logged 10.9 inches of rain accumulated by mid-year, with June the heaviest month at up to 7.6 inches, a figure the state had not seen since around 2018. The rainy season opened in the middle of May. The state’s own water engineers warned before it started that June would be the wettest month, and warned specifically about standing water, urban flooding and arroyos overflowing their banks. CONAGUA had forecast in April that El Niño would push 2026 past 2025, which was already one of the wettest years of the decade.
Now put that beside the illness curve. Back the six-week reporting lag off the late-June surge in reported cases and the excess illnesses in this outbreak begin in the back half of May. The rains began the week of May fourteenth. June, the month the state water engineers said would be the wettest, is the month the reporting exploded.
That is a temporal correlation and nothing more. Statewide rainfall is not Doctor Mora rainfall, and the station data that would settle it sits with CONAGUA. I have not found a single published report of a sewage system overflowing or a treatment plant bypassing in Doctor Mora or San José Iturbide this spring. I am not going to claim one happened. What I will say is that perhaps nobody has looked, and that the absence of a news story about a rural Mexican sewer is not evidence about a rural Mexican sewer.
Here is why the mechanism fits, though, and it fits better than anything else. This parasite has one known reservoir, and it is human feces. FDA’s own report says so in its second paragraph. Heavy rain is how human waste gets out of septic tanks and sewers and into arroyos and onto open ground — that is not a Mexican problem, it is a plumbing problem, and it happens in Iowa. An unlined elevated holding pond is a catchment. And then comes the detail that makes a pond different from every other point on this map: the oocysts shed in faces are not infectious when they leave the body. They need one to two weeks somewhere warm, between 72 and 90 degrees Fahrenheit, to sporulate. Northeastern Guanajuato sits inside that temperature window in every month of the year.
A holding pond is warm, still, open and full for weeks at a time. It is not merely a place where contamination could enter the irrigation system. It is a place with exactly the residence time and exactly the temperature this organism requires to become infectious. If you were designing an incubator for Cyclospora and then attaching it to a lettuce field, you would build something that looked a great deal like an unlined irrigation reservoir in central Mexico in June.
The plant is at kilometer 16 of the Doctor Mora to San Miguel de Allende highway. Seven hundred and seventy-six feet away sits Balneario Las Fajanas, a public thermal bathing complex the state of Guanajuato lists in its own tourism guide, with pools, water slides, grills, palapas and restrooms, open every day of the week. I have written about that before. Within nine miles there is a second bathing complex, a water park, two municipal treatment works and two towns. What I cannot show you is the thing this post is actually about, because the five ranches in FDA’s report are lettered A through E and their locations have never been published. The ponds are somewhere in that landscape and nobody outside the company and two governments knows where.
None of this is a novel theory. The Center for Produce Safety and USDA have been funding work on exactly this premise — faulty septic systems, compromised sewer pipes and treated effluent reaching surface water used to irrigate food crops. A two-year study in southeast Georgia confirmed the parasite by sequencing in nine percent of municipal wastewater sludge samples. In 2020 FDA came closer to proving it than it ever has, sampling a regional canal in Florida during the Fresh Express bagged salad outbreak and finding the parasite at two points, north and south of where the suspect farm drew canal water for irrigation. The genetic typing was not mature enough to match those finds to patients, and the investigation closed unresolved. And in 2015 FDA published an import alert on Puebla cilantro describing human feces and toilet paper in growing fields, and wash water vulnerable to sewage, at eight of eleven farms inspected.
There are four documents that would settle most of this and none of them requires anyone to speculate. The CONAGUA station records for Doctor Mora and San José Iturbide, which would say what rain actually fell where. The municipal discharge and bypass records held by the state water commission and the San José Iturbide utility, which would say whether anything overflowed. The locations, linings and sampling histories of the irrigation holding ponds serving the 2026 crop — Taylor Farms has these, and FDA has seen their 2013 ancestors. And the answer to the question FDA asked Taylor Farms thirteen years ago, in recommendation two of that same report: is Cyclospora a reasonably likely hazard in the Guanajuato growing region, and if it is, what happened to the wash step?
Twenty-two thousand people have been counted this season by their own state health departments. Two of them are dead. I am not in a position to tell you that a pond did this, and I have tried to be careful above about the difference between what a federal report from 2013 says and what I think it implies. But when the industry answers a question about irrigation water with the word well, somebody should point out that FDA already wrote down what happens to the water after it leaves the well. It goes into a pond. Sometimes the pond has no liner. And it sits there in the sun, in a valley where the temperature never leaves the range this parasite needs, until somebody opens a valve.











