In a study taking place in an urban slum setting in Salvador, Brazil, it has been found that open sewers, refuse accumulation, and inadequate floodwater drainage are sources for the transmission of the disease leptospirosis. This study was published on April 23, 2008 in the open source in the open-access journal PLoS Neglected Tropical Diseases.

Caused by the bacterium Leptospira, Leptospirosis is transmitted via contact with animal reservoirs or through water and soil contaminated with animal's urine. The severity of the disease can be as low as a mild, flu-like illness to life-threatening forms of the diseases, such as Weil's disease, which kills one in ten people, and severe pulmonary hemorrhage syndrome, which kills over one of two. Urban slum communities, which have gown considerably worldwide, have provided conditions for rodent-borne transmission.

To investigate how these environments have influenced the disease's transmission, Dr Albert Ko (Centro de Pesquisas Gonçalo Moniz, Fundação Oswaldo Cruz, Ministério da Saúde, Salvador, Brazil) and colleagues examined 3,171 slum residents for Leptospira antibodies, which would indicate a previous infection with the bacterium. Then, Geographical Information System (GIS) and modeling approaches were used to identify problems in the sanitation infrastructure of the slum, as linked to Leptospira infection. Additionally, they looked for correlation between infection and poverty.

The group found that households with instances of Leptospira antibodies tended to cluser in areas of squatters at the bottoms of valleys. In particular, the risk of aquiring the antibodies was higher in people living in flood-risk regions with open sewers, or near accumulated refuse, and those who saw rats or lived in the presence of chickens. Additionally, poverty was a risk factor for infection, with an increse of US$1 per day in per capita household income was linked to an 11% decrease in infection risk.

The authors conclude with comments about future policies that should arise from these results. "These findings indicate that effective prevention of leptospirosis will need to address the social factors that produce unequal health outcomes among slum residents, in addition to improving sanitation."

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Impact of Environment and Social Gradient on Leptospira Infection in Urban Slums.
Reis RB, Ribeiro GS, Felzemburgh RDM, Santana FS, Mohr S, et al.
PLoS Negl Trop Dis 2(4): e228.
doi:10.1371/journal.pntd.0000228
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Anna Sophia McKenney