The Stealth Disease Stalking Farmworkers

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The tropical sun was beating down on Homestead, a city on the southern tip of Florida, when Valerie Mac, a nurse-scientist and occupational health specialist from Emory University, pulled her van into the driveway of a small vegetable farm. Its owner, Isidoro Quezada, walked out to greet her, his arms caked with dirt and his face streaked with sweat and grime.

Mac and her two research assistants followed Quezada into his home, where they sat him down to take his temperature, blood pressure, and heart rate and instructed him to provide a urine sample. They also drew his blood, placing the vial into a portable analysis machine. “We process it,” Mac says, “pretty much like you would do in a hospital or a lab, and then we put it on dry ice right away to preserve it and get it back to the school to analyse it.”

But on this particular day in August, with the mercury pushing past 90F, the machine kept overheating. The irony was not lost on Mac and her crew, who were in South Florida gathering data for a study about the way extreme heat conditions affect the bodies of agricultural workers. More specifically, they’re looking for signs of stress on the kidneys, which can lead to a disease called chronic kidney disease of unknown origin, or CKDu.

As its name indicates, the causes of CKDu are poorly understood. What’s not in question is that it’s deadly. Symptoms—including vomiting, exhaustion, and weight loss—often don’t appear until the disease is well-advanced, by which time damage to the kidneys cannot be reversed. Without access to dialysis or a kidney transplant, there is little hope of survival.