Biomarkers of Kidney Injury Among Nicaraguan Sugarcane Workers.

BACKGROUND: In Central America, an epidemic of chronic kidney disease of unknown cause disproportionately affects young male agricultural workers. STUDY DESIGN: Longitudinal cohort study. SETTING & PARTICIPANTS: 284 sugarcane workers in 7 jobs were recruited from one company in northwestern Nicaragua. Blood and urine samples were collected before and near the end of the 6-month harvest season. PREDICTORS: Job category (cane cutter, seeder, seed cutter, agrichemical applicator, irrigator, driver, and factory worker); self-reported water and electrolyte solution intake. OUTCOMES & MEASUREMENTS: Changes in levels of urinary kidney injury biomarkers normalized to urine creatinine level, including neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), N-acetyl-ß-d-glucosaminidase (NAG), and albumin; serum creatinine-based estimated glomerular filtration rate (eGFR). RESULTS: Mean eGFR was 113 mL/min/1.73 m(2) and <5% of workers had albuminuria. Field workers had increases in NGAL and IL-18 levels that were 1.49 (95% CI, 1.06 to 2.09) and 1.61 (95% CI, 1.12 to 2.31) times as high, respectively, as in non-field workers. Cane cutters and irrigators had the greatest increases in NGAL levels during the harvest, whereas cane cutters and seeders had the greatest increases in IL-18 levels. Electrolyte solution consumption was associated with lower mean NGAL and NAG levels among cane cutters and lower mean IL-18 and NAG levels among seed cutters; however, there was no overall effect of hydration among all workers. On average, workers with the largest increases in NGAL and NAG levels during the harvest had declines in eGFRs of 4.6 (95% CI, 1.0 to 8.2) and 3.1 (95% CI, -0.6 to 6.7) mL/min/1.73 m(2), respectively. LIMITATIONS: Surrogate exposure measure, loss to follow-up. CONCLUSIONS: Results are consistent with the hypothesis that occupational heat stress and volume depletion may be associated with the development of kidney disease, and future studies should directly measure these occupational factors. The presence of urine tubular injury markers supports a tubulointerstitial disease that could occur with repeated tubular injury.

Investigating Possible Infectious Causes of Chronic Kidney Disease of Unknown Etiology in a Nicaraguan Mining Community.

A chronic kidney disease of unknown etiology (CKDu) has been killing workers in Central America. Occupational heat stress is thought to play an important role. Leptospirosis and hantavirus have been suggested as additional possible risk factors. In a case-control study in a Nicaraguan mining community, a structured survey was administered to adults, and biological measurements and specimens were taken. Serum was analyzed for antibodies to Leptospira and hantavirus. Before statistical analysis, a board-certified nephrologist determined final case and control status based on serum creatinine and other laboratory values. Multivariable analysis was by logistic regression. In sensitivity analyses, cases were restricted to those diagnosed with CKDu in the previous 3 years. Of 320 eligible participants, 112 were classified as presumptive cases, 176 as controls and 32 as indeterminant. The risk of CKDu in those ever having worked in mining or construction was 4.4 times higher than in other participants (odds ratio = 4.44, 95% CI: 1.96-10.0, P = 0.0003). Eighty-three (26%) of the 320 participants were seropositive for at least one tested strain of Leptospira. No evidence of a causal link between leptospirosis or hantavirus and CKDu was found. The sensitivity analyses provide some evidence against the hypotheses that leptospirosis or hantavirus leads to CKDu within a few years. A major limitation was the impossibility of determining the absolute or relative timing of infection and CKDu onset. A prospective cohort design, with repeated collection of specimens over several years, could yield clearer answers about infections as potential etiologic agents in CKDu.

Leptospira seropositivity as a risk factor for Mesoamerican Nephropathy.

BACKGROUND: Leptospirosis is postulated as a possible cause of Mesoamerican Nephropathy (MeN) in Central American workers. OBJECTIVES: Investigate job-specific Leptospira seroprevalence and its association with kidney disease biomarkers. METHODS: In 282 sugarcane workers, 47 sugarcane applicants and 160 workers in other industries, we measured anti-leptospiral antibodies, serum creatinine, and urinary injury biomarkers, including neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), and N-acetyl-D-glucosaminidase (NAG). RESULTS: Leptospira seroprevalence differed among job categories and was highest among sugarcane cutters (59%). Seropositive sugarcane workers had higher NGAL concentrations (relative mean: 1.28; 95% CI: 0.94-1.75) compared to those who were seronegative, with similar findings among field and non-field workers. CONCLUSIONS: Leptospira seroprevalence varied by job category. There was some indication that seropositivity was associated with elevated biomarker levels, but results were inconsistent. Additional studies may help establish whether Leptospira infection plays any role in MeN among Central American workers.

Changes in kidney function among Nicaraguan sugarcane workers.

BACKGROUND: There is an epidemic of chronic kidney disease (CKD) of unknown etiology in Central American workers. OBJECTIVES: To investigate changes and job-specific differences in kidney function over a 6-month sugarcane harvest season, explore the potential role of hydration, and measure proteinuria. METHODS: We recruited 284 Nicaraguan sugarcane workers performing seven distinct tasks. We measured urine albumin and serum creatinine and estimated glomerular filtration rate (eGFR). RESULTS: eGFR varied by job and decreased during the harvest in seed cutters (-8·6 ml/min/1·73 m(2)), irrigators (-7·4 ml/min/1·73 m(2)), and cane cutters (-5·0 ml/min/1·73 m(2)), as compared to factory workers. The number of years employed at the company was negatively associated with eGFR. Fewer than 5% of workers had albumin-to-creatinine ratio (ACR) >30 mg/g. CONCLUSIONS: The decline in kidney function during the harvest and the differences by job category and employment duration provide evidence that one or more risk factors of CKD are occupational.

Prevalence of untreated schistosomiasis among Sudanese refugees: "The Lost Boys of Sudan" in the United States

Background. The increase in global travelling also brings infections from endemic to non-endemic regions where diagnosis and treatment may be delayed. Methods. From 2005 to 2008, 104 Sudanese refugees were evaluated to determine the prevalence of untreated schistosomiasis at the Tropical Medicine Clinic at Emory University in Atlanta, GA. Sera from 87 patients were screened using FAST-ELISA and antigen-specific immunoblots. Results. Of the 87 patients screened, 44.8% were positive for schistosomiasis antibodies, including Schistosoma mansoni and S. haematobium. Conclusion. Our study emphasizes the need for single-dose presumptive treatment of praziquantel among sub-Saharan refugees and long-term travelers.