Logging roads have brought a higher incidence of diarrheal disease and new social problems among communities along the Ecuadorian coast, according to a new study by an international research team led by Joseph Eisenberg, assistant professor of epidemiology at the University of Michigan School of Public Health. The new roads connect Ecuadorian villages that previously used only rivers for transport.
The study suggests the importance of considering human costs when assessing the environmental impacts of large development projects. With funding from the National Institutes of Allergy and Infectious Disease, the research team examined diarrheal infections and social networks in 21 villages being connected to a new road network built by the Ecuadorian government at the southern end of the Chocó rainforest, near the Pacific Ocean and the border with Columbia.
The roads bring new people to the villages, and allow the villagers to travel more easily between villages, and also back-and-forth to larger cities. But bacteria, viruses and parasites hitch rides with the newly-mobile people, adding new strains of old bugs to the local environment and increasing infection rates, according to Eisenberg. "If you keep reintroducing strains of a given pathogen, you're increasing the endemic population of pathogens," he said.
The study looked in particular at E. coli bacteria, rotavirus and the protozoan parasite Giardia, finding different infection rates and modes of transmission for each, but the same overall trends: proximity to the road meant higher infection rates. Remote villages were found to have infection rates up to eight times lower than those close to the new road.
"The increased diversity and potency of the microbe population apparently offsets the improved health care that also comes with new roads," he said. "When you're thinking about a road, you have to also think about these impacts that will take years to unfold."
The newly busy towns also seemed to experience a breakdown of traditional social structure and supports, leading to poorer sanitation, Eisenberg said. Borbón, the boom town at the hub of the new road network, has grown to more than 1,000 homes and has an ominous "fecal film" on its river.
"When the tide goes down and you look at the river bank, you can see a number of pipes leading from all sorts of buildings," Eisenberg said.
To gather these measures, the team's surveyors visited each village three times over the course of two years. During each 15-day visit, they stopped at every home daily, asking if anyone was sick and collecting stool samples to identify the organism causing the illness.
In addition to tracking the movement and identity of diarrheal diseases, they interviewed all the villagers about their social contacts and built a social network map as a way to measure social cohesion. Social cohesion affects the maintenance of infrastructure, which is relevant to disease transmission, Eisenberg said. "The higher social cohesion is, the cleaner the village," he said.
Numerous studies have linked infectious disease with roads and road construction, including HIV transmission in Uganda and malaria in Peru, but the effects of roads on diarrheal diseases, which are a leading cause of mortality among infants and children under age 5, are relatively unknown.
The study "Environmental change and infectious disease: How new roads affect the transmission of diarrheal pathogens in rural Ecuador" appears in the Proceedings of the National Academy of Sciences the week of Dec. 4. Authors include colleagues from the University of California at Berkeley, Universidad San Francisco de Quito, Ecuador, and Trinity College in Hartford, Conn.
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