Are fecal indicator bacteria appropriate measures of recreational water risks in the tropics: A cohort study of beach goers in Brazil?

Regulating recreational water exposure to pathogens within the tropics is a major public health and economic concern. Although numerous epidemiological studies estimating the risk to recreational marine water exposure have been conducted since the 1950s, few studies have been done in the tropics. Furthermore, many have suggested that the use of fecal indicator bacteria for monitoring recreational water quality in temperate regions is not appropriate in the tropics. We analyzed a large cohort study of five beaches in Sao Paulo, Brazil, conducted during consecutive weekends in the summer of 1999 that estimated risk to water, sand, and food exposures. Enterococci and Escherichia coli concentrations were measured each day of the study. Elevated risks were estimated for both swimming (OR = 1.36 95% CI: 1.05-1.58) and sand contact (OR = 1.29 95% CI 1.05-1.58). A 1 log increase in enterococci concentration was associated with an 11% increase in risk (OR = 1.11 95% CI: 1.04-1.19). For E. coli a 1-log increase in concentration was associated with 19% increase in risk (OR = 1.19 95% CI: 1.14-1.28). Most countries with beaches in the tropics are lower or middle income countries (LMIC) and rely on tourism as a major source of income. We present data that suggests fecal indicator bacteria such as enterococci are an appropriate indicator of risk in tropical urban settings where contamination is coming from predominantly human sources. Additional studies in tropical settings could help inform and refine guidelines for safe use of recreational waters.