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Talking back

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The Riddle of What Is Killing Thousands of Central American Cane Workers

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Cane worker in Nicaragua

“Why the Silence Comandante Ortega?”

That paraphrasing of a headline from the great Spanish daily El Pais introduced a story in the paper on the difficulties that Nicaragua has faced in coming to grips with the death and disability wrought by a still-unexplained kidney disease epidemic. By one estimate, at least 20,000 men throughout Central America and Mexico have met premature deaths during the last 20 years from kidney failure, many of the victims cane workers laboring in the oppressive heat of the Pacific lowlands.

The El Pais headline challenged Daniel Ortega, the Sandinista president, and purveyor of populist slogans like “arriba los pobres del mundo,” to take a more active role in addressing the crisis. Tensions over what has come to be known as Mesoamerican nephropathy came to a head on Jan. 18 when a group of former cane workers suffering from the kidney condition staged a protest at the gates of the facility owned by Nicaragua Sugar Estates Limited in the northwestern town of Chichigalpa. At some point, police opened fire, killing one man and injuring three others. one of whom was a teenage boy.

Three police who fired their weapons were criminally charged—and the government did dispatch a minister to address the group's demands. But the epidemic that drove the men to the streets persists, not only in Nicaragua, but also for cane cutters and sometimes other manual laborers along the length of Pacific coast reaching as far as southern Mexico. Workers affected often die from end-stage kidney disease in a region ill-equipped with dialysis or transplantation programs.

One of the first entries of Mesoamerican nephropathy into the scientific literature appeared in 2002 when a paper noted that nearly 70 percent of patients at Rosales Hospital in San Salvador had advanced kidney disease without the hypertension or diabetes that usually precede the illness.

In the last 20 years, the rate of all chronic kidney disease in Nicaragua and El Salvador has been roughly 42 deaths per 100,000, three times higher for men than for women. Another statistic also points to something amiss—either in working conditions or chemical exposures. The mortality rate from chronic kidney disease in Nicaragua and El Salvador is 17 times higher than in Cuba, another sugar-producing nation. The impact of the disease can devastate whole communities. La Isla in Nicaragua, where many sugar workers live, is known as “La Isla de Viudas”—The Island of Widows—because funerals for the men are so common.

Dehydration from the brutal heat of the cane fields is the leading suspect—check out the photo above. Richard Johnson of the University of Colorado, Denver, and colleagues have been pursuing the hypothesis that dehydration of cane workers causes an enzyme to be activated within the kidney’s tiny tubules, converting glucose to fructose. The fructose then gets metabolized by another enzyme, fructokinase, to produce oxidants that cause inflammation and scarring that may be the basis for the illness. Soft drinks and mango or pineapple juice with added sugar may increase fructose levels and attendant inflammation, leading to what Johnson has described as a “local holocaust.” (Johnson has received funding from Groupe Danone, the French food-products company, for a yet-to-be-published study to assess the effects of hydration on Nicaraguan cane workers.)

Other factors could also play a role, perhaps exacerbating the effects of dehydration. The list of possibilities includes heavy metals, agrochemicals, overuse of anti-inflammatory medications and contaminated alcohol. No consensus has emerged about the most likely culprit. Even the dehydration thesis is suspect, as sweat and thirst are a mainstay of field work. “From my experience when people say it’s multifactorial, that means that people don’t really know what’s going on,” says Peter Jay Hotez, dean of the National School of Tropical Medicine at Baylor University. “Most things are not multifactorial.” Hotez suggests the possibility that the illness may result from leptospirosis (a bacterial infection), hantavirus or perhaps another communicable disease.

Preventive measures to assess workers' kidney function is one option. “Pre-symptomatic diagnosis is actually not that difficult,” says Daniel Brooks, associate professor in the department of epidemiology at the Boston University School of Public Health, which has been contracted to study the epidemic. “A blood test for serum creatinine is a very good screening measure and a number of companies in the region employ it.” (Some of the funding for Brooks's research has come from a fund to research chronic kidney disease, partially supported by the the Comite Nacional de Productores de Azucar.)

Desperate to earn a $5-a-day wage, workers unable to pass the test will often find ways to make it into the fields by teaming up with a subcontractor. The recognition that many workers will find any means possible to earn money by cutting cane has drawn attention to conditions in the fields. “There’s no harder job than sugar cane,” says Jason Glaser, president of La Isla Foundation, a Nicaraguan-based NGO. “The heat is intense in the lowlands and these guys are out in 95 to 105 degrees in the heat for up to 12 hours a day.” La Isla is involved in both research and advocacy for better conditions—more frequent water breaks in the shade, among other measures.

The epidemic is now drawing international attention. Three workshops have been held since 2005 and new scientific papers appear regularly. The Consortium on the Epidemic of Nephropathy in Central America and Mexico formed after the last workshop in 2012 to foster collaboration among researchers. The Centers for Disease Control and Prevention in Atlanta has set up a task force. Another NGO, Solidaridad, in a collaboration with La Isla Foundation, received a 3 million-euro grant in February to work toward eradicating the disease, funding from a Dutch lottery that raises money for charitable endeavors.

Kidney diseases of unknown origin are not a new occurrence. During the latter half of the twentieth century, Balkan endemic nephropathy perplexed epidemiologists in countries along the Danube until it was discovered that toxic aristolochic acid was contaminating wheat flour. Recent cases of unexplained chronic kidney disease have been identified in Sri Lanka, leaving a group of researchers to note recently in an editorial in The American Journal of Public Health that the disease “is probably a hitherto unrecognized global problem, although it is not clear if the … epidemics observed in other parts of the world are the same disease or are caused by the same factors as in Mesoamerica.” Epidemiologists and nephrologists are going to be spending a lot of time together for years to come.

Credits:

Piet den Blanken and La Isla Foundation (photo).

Tierra Unida Films and La Isla Foundation (video)

The views expressed are those of the author and are not necessarily those of Scientific American.

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