A mysterious kidney disease is striking down labourers across the world and climate change is making it worse. Jane Palmer meets the doctors who are trying to understand it and stop it.

By 10am in the sugarcane fields outside the town of Tierra Blanca in El Salvador, the mercury is already pushing 31°C. The workers arrived at dawn: men and women, young and old, wearing thick jeans, long-sleeved shirts and face scarves to prevent being scorched by the sun’s rays. They are moving quickly between rows of cane, bending, reaching, clipping and trimming in preparation for harvesting the crop in the weeks to come. In the scant shade, old Pepsi and Fanta bottles full of water swing from tree branches, untouched. Gulping only the thick air, the workers won’t stop until noon, when their shift is over. Among them is 25-year-old Jesús Linares. His dream, he explains in English, was to be a language teacher, but like many Salvadoran children he went to work to help support his parents and siblings. Aged eight, he learned to hide in the towering canes whenever the police sought out underage workers; since then, he’s tended sugarcane from dawn to noon and then pigs until dusk. In the evenings, he tries to listen to English audio programmes or read a language book, but for the last year he’s been too tired to concentrate. So tired, in fact, that a few months ago he visited the Tierra Blanca clinic. Blood tests revealed that Linares was in the early stages of chronic kidney disease. It’s a familiar story here in the Bajo Lempa region, where recent studies suggest that up to 25 per cent of its nearly 20,000 inhabitants have chronic kidney disease. Across El Salvador, kidney failure is the leading cause of hospital deaths in adults. But while chronic kidney disease is most commonly caused by hypertension and diabetes, two-thirds of patients in Bajo Lempa don’t have either of those conditions, and the cause of their illness remains uncertain. Scientists have identified certain key themes. The majority of people with the unexplained disease are men, and it strikes predominantly in hot, humid regions where people are engaged in strenuous outdoor labour: farming, fishing or construction work. Dehydration, which seems an obvious factor, causes acute kidney disease that is easily reversed by drinking water, rather than this chronic form. This has left two burning questions: what causes this new form of kidney disease, and will it be likely to spread as the world gets warmer? Meanwhile, in El Salvador over the last two decades, more and more patients have arrived at clinics and hospitals, often taxing them to their limit. Many people, unable to get treatment, simply return to their homes to die. “This is really a silent massacre,” says Ramón García-Trabanino, a Salvadoran kidney specialist. © Brett Gundlock/Boreal Collective

You don’t feel any kind of pain, but you feel like you are slowly decaying The patients at the Hospital Nacional Rosales in San Salvador all have the same story: until three months ago they were perfectly fine. Most of them had never seen a doctor in their life before, and had ignored any early signs of ill health this time as well. The turning point came only when they were too sick to work. Working hard lies at the heart of Salvadoran culture. During the 1980–92 civil war, the armed forces carried out a scorched-earth strategy, targeting the civilian population in the countryside to remove any possible support base for the rebels. Tens of thousands died and a quarter of the populace fled. When peace finally came, the rural communities were able to return to their land, which was parcelled out to cooperatives, industry and independent farmers. For the survivors, the only way forward was to work, and work hard, to overcome other challenges that peace could not resolve. © Brett Gundlock/Boreal Collective At 8,124 square miles, El Salvador is one of the world’s smallest countries, yet within its boundaries lie endless stretches of coastline, mountain ranges and an abundance of agricultural lowlands, which owe their fertility to rich volcanic soil. There are 23 volcanoes in El Salvador, standing over the cities and central plateaus like guardians. In 2013, people in the San Miguel province fled their homes when the Chaparrastique volcano began spewing hot ash and smoke into the air. Volcanoes aren’t the only natural hazard. The country sits right where the western part of the Caribbean Plate overrides the Cocos Plate, making it one of the most seismologically active regions on earth. In 2001, two earthquakes south-west of San Miguel killed at least 1,000 people and destroyed or damaged nearly 300,000 homes. Such challenges only add to the determination to work hard, and in keeping with this cultural work ethic, many agricultural labourers don’t admit to getting ill, even to themselves. But kidney disease is a sneaky opponent. It can totally destroy one kidney while the individual remains blissfully unaware. Only in the final stages of the disease do the workers get a hint that all is not well, and by the time they arrive at the emergency ward, they are dying. García-Trabanino started a fellowship at the Rosales hospital as a young doctor in 1998, and what he encountered resembled a scene from a battlefield. He had expected to be treating heart disease, neurological patients, eye problems – the full gamut of medical conditions. Instead all he encountered were men dying – sometimes slowly, but usually quickly – from kidney failure. They came in such numbers that they overwhelmed the beds and spilled into the corridors. © Brett Gundlock/Boreal Collective “Sometimes, even with [our] obsolete dialysis techniques, we managed to get some of them to survive a night. A day. A week,” he says. Most died within a month, however, and no one seemed interested in finding out why, or even how many cases there were. So García-Trabanino and a colleague started counting them, one by one, at the door of the emergency ward until, after a few months, their count reached more than 200. The Ministry of Health in El Salvador didn’t follow up on their findings, but it did grant the doctors a medal, which garnered media attention. “The next month people from the social organisations of the coastlands came,” García-Trabanino recalls. The visitors told him stories of years of living with unexplained deaths among their otherwise healthy young people. Every other week they had to burn the dead. “You’ve just discovered what we have been living for years,” they said. “Tell me, doctor, what is the cure?” He had no answer. Today, the hospital has 1,000 cases of chronic kidney disease, with more than 30 new patients arriving each month. “But we only have resources for half of them,” says Ricardo Leiva, head of the nephrology unit. By the time the new victims arrive they typically need dialysis, but the waiting list is long. Sometimes the nephrologists can administer peritoneal dialysis instead, using a hard plastic tube inserted into the belly by surgery. “It is an old technique that is not being used anywhere else in the world,” says Leiva. “But we need it.” Back in Tierra Blanca, Juan Pablo Paniagua, a lean 60-year-old with a permanent toothy grin, talks about how the disease caught him totally by surprise. Working in the cornfields since he was a boy, then as a fisherman, he felt fine until seven years ago. “Then your body starts feeling something strange. You don’t know what it is,” he says. “You don’t feel any kind of pain, but you feel like you are slowly decaying.” Paniagua received dialysis three times a week for two and a half years. After that, he was unable to pay for the regimen, which typically runs to about $120 for a single blood-cleansing session. So the doctors showed him how to take care of a catheter in his abdomen and instructed him in how to do peritoneal dialysis at home. “I’ve had moments of nearly dying but,” he says, “once I started dialysis, I realised that I was actually improving.”

We realised the problem was all across Central America and southern Mexico Early in 2016, 32-year-old José Luis Morales, a healthy-looking man with a footballer’s physique, began to feel cramps in his legs and became so weak he couldn’t pick up a glass of water. Morales works as a truck driver in Chalatenango, a humid lowland area in northern El Salvador and another hotspot for chronic kidney disease. Unable to work, he went to San Salvador to see García-Trabanino. “He had the classic picture of this disease,” García-Trabanino says. “He is not diabetic, he is not hypertensive. He is young without any past medical history.” Blood tests revealed low potassium and high uric acid levels, which García-Trabanino treated with medication. Currently in stage two of the disease, Morales will need to take medication for the rest of his life. “We can’t revive or bring back to life the lost kidney tissue, but we can take care of what is left,” says García-Trabanino. Chronic kidney disease destroys kidney tissue until it can no longer filter waste from the blood. Without dialysis, this can lead to high blood pressure, weakness, dizziness and a host of other symptoms. But while diabetic kidney disease damages the glomeruli, the tiny units that clean the blood, the new form destroys the renal tubules, where urine is made and transported, and the interstitium, which surrounds the other structures in the kidneys and helps maintain the right balance of fluid. This is the same pattern of damage caused by some toxins, and because the new disease hit the agricultural communities so heavily, García-Trabanino suspected that exposure to herbicides and insecticides might be to blame. © Brett Gundlock/Boreal Collective To investigate, he teamed up with the Emergency Social Fund for Health in Tierra Blanca, as well as with Emmanuel Jarquín, an occupational health and safety consultant. Together, they investigated the incidence of chronic kidney disease in agricultural labourers in the lowlands, and compared them with similar workers in a region 500 metres above sea level. In the latter group, however, they found almost no cases of the mysterious disease. “They were working the same crops and using the same chemicals, but they were not getting sick,” García-Trabanino says. “We were clueless.” The physicians began to wonder if they were just seeing a local problem, as most of the patients in Rosales hospital had come from the Bajo Lempa region. So Jesús Domínguez, a Spanish volunteer physician in Tierra Blanca, went on a mission. Renting a car and equipment, he drove from Mexico to Nicaragua, stopping by fields and taking urine samples from outdoor labourers toiling under the sun. His study indicated that many of the workers were already in the first stages of chronic kidney disease. Far from being local, says García-Trabanino, “we realised the problem was bigger than we thought, and it was all across Central America and southern Mexico”.