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Study links sugarcane fieldwork with kidney disease epidemic in Central America

February 17, 2015

See also: What is killing the young men of Cañas?

Scientists are now a little closer to uncovering the cause of a chronic kidney disease (CKD) epidemic that has killed more than 20,000 people in Central America in the last two decades. For years, the cause of the disease — which primarily afflicts young male agricultural workers — has stumped doctors. But a new study from the Boston University School of Public Health found that sugarcane fieldwork could play a role.

“Our results provide evidence that one or more factors for this CKD epidemic are occupational,” said Rebecca Laws, a doctoral student at Boston University and one of the study’s authors. “We found that sugarcane workers saw a decline in kidney function during the harvest season and that it varied by job category.”

Laws and her team studied 248 sugarcane workers in western Nicaragua, the epidemic’s hot spot, during the sugarcane-harvesting season. They measured the workers’ kidney functions before and after the harvest season and compared results from workers in seven different jobs. Their results were released in the International Journal of Occupational and Environmental Health on Jan. 28. The study showed that fieldworkers, particularly those in who worked as cane cutters, seed cutters or irrigators had lower kidney function at the end of harvest season than other workers. The study points to heat exhaustion and dehydration from fieldwork as possible causes for the epidemic.

Unlike CKD in the United States and other developed countries, the disease is not linked to hypertension or diabetes and tends to affect otherwise healthy men. Concentrated in rural parts of Nicaragua, El Salvador, Costa Rica and Guatemala, the disease often is understudied and receives little attention.

“There are just not enough resources in the region right now to treat the disease,” Laws said. “Unfortunately, right now, usually the disease is fatal.”

In Costa Rica, the northwestern province of Guanacaste has the highest rates of CKD. The small agricultural town of Cañas, in the province’s center-east, has CKD rates 18-20 times higher than the rest of the country. Most of the men in the area work for the local sugarcane plantation, Ingenio Taboga. Representatives from the company declined to comment for this story.

Though farmworkers have been silently suffering from CKD since the 1970s, the disease’s staggering rates did not become apparent until the early 2000s. As scientists struggled to pin down a cause for the disease, local theories about the epidemic’s origin have run wild. Most in the Cañas area point to pesticides or arsenic as probable causes of CKD. Drinking water in parts of Guanacaste has tested with 13 times more arsenic than what the World Health Organization deems as safe, and sugarcane is heavily treated with chemicals. But both theories to date have little scientific support.

Though arsenic is a known carcinogen, it has never been linked with kidney disease, and if the toxin’s presence in the water supply was the only cause, both men and women likely would be affected. The Boston University study also has put a dent in the pesticide theory, as men who worked applying agrochemicals saw the least decline in kidney function over the harvest season. Still, public health researchers say the disease is likely the convergence of multiple factors, and pesticides and arsenic have not been ruled out entirely.

Laws is now working on two more studies in Nicaragua that could help uncover more about the CKD epidemic. One, a longitudinal study, will compare sugarcane workers with farmhands in other types of agriculture. The other study will look at renal damage in children and adolescents to help identify possible genetic factors in the disease. But while more research and time are required to nail down the full cause of the disease, men all over Central America are dying.

“Additional research will take time, so it is really important to take action to address the epidemic now,” Laws said. “Even if fieldwork ends up being less of a factor than we think, these men will benefit from improved working conditions now.”

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