By A.J. O’Connell
Twenty years ago, Ecuador built a new highway. The road ran from the north coast of the country to the mountains and connected the remote coastal province of Esmeraldas to the rest of the country.
The highway brought a lot of change quickly: electricity, development, logging, and an unwanted hitchhiker: disease.
Scientists from six colleges in the US and Ecuador have been studying the impact of that road on 21 rural villages for the past 15 years in a wide-ranging program called Eco Dess, which stands for Ecología Desarrollo, Social y Salúd – or in English, Ecology, Development, Social, and Health.
Last year, Eco Dess received its latest funding: a grant from the National Institutes of Health to research the highway’s effect on the spread of Zika virus and Dengue Fever.
He said the appearance of Dengue shows that the area, while still rural, is urbanizing.
“We’re interested in what it means to be urban and why,” he said.
Diseases are more than microorganisms. They’re pathogens spread by people. Choices made by the communities affected by the diseases influence who is infected, how many disease vectors there are, and how the disease spreads.
“Exposure to the viruses that cause Dengue and Zika is a product of human behavior and mosquito behavior,” said James Trostle of Trinity College in Hartford, Conn., a long-time member of the Eco Dess research team.
Trostle, an anthropologist, is one of Eco Dess’s principal investigators. He’s been with the project since 2003.
It’s Trostle’s job to study the human behavior in the equation. He focuses on the way social networks influence the spread of disease, how human behavior helps mosquito populations flourish, and how rural and and urban development – road building in this case – draw people and mosquitos together.
“We’re studying these infections because, like many infectious diseases, population movements influence their spread,” he said. “Roads help new infectious strains to travel to new places and infect new unexposed people. But we still don’t understand how or for how long these effects last.”
The roads at the heart of the project are the E15, the E10, and the E20: highways Ecuador built between 1996 and 2002. Before the highway, travellers could only reach the 12 parishes and 120 villages in Cantón Eloy Alfaro – an area of the coastal Esmeraldas province – by boat, travelling to the area from the Pacific Ocean and up through the delta of the local rivers.
“In 1996, the road connected this region to the coast,” said Eisenberg. “By 2002, it connected [the region] to the Andes.”
Studies had been done in the past on the effects of road-building on sexually transmitted diseases in rural areas. But Eisenberg – who started studying the road as it was being built in 2000 – wanted to take his research in a different direction. He wanted to understand how the road was influencing the spread of diarrheal diseases.
This current phase of the project studies the spread of both the Zika Virus and Dengue Fever, related infections spread by the same species of mosquito. Neither disease has a cure or vaccine.
Zika is the more recognizable of the two diseases; the virus gained notoriety in 2015, when infants in Brazil were born with microcephaly, a condition that impairs the development of the brain, resulting in, among other symptoms, a smaller-than-usual head. The microcephaly was tied to the Zika Virus, and there have been significant efforts in the last three years to protect pregnant women from Zika, especially since some cases have been reported in the US.
When it comes to mortality, however, Dengue is the more dangerous disease. Discovered more than 150 years ago, Dengue Fever causes close to 22,000 deaths a year, according to Trostle. About 50-100 million Dengue cases are reported annually.
“Zika scares us more than Dengue even though it is less deadly and less common than Dengue,” he said.
The effects of the road development have been wide-ranging, and over the years Eco Dess has expanded to include several areas of study, such as environmental change, drinking water quality, antibiotic resistance, chicken-keeping and community structure.
“The strength of the Eco Dess project is that we can study both local and larger scale phenomena within the same study,” said Dr. Karen Levy, an associate fellow at Emory University’s Rollins School of Public Health. Levy studies household water quality, the impact of climate on waterborne disease, and local chicken-keeping’s role in passing on antibiotic resistance with Eco Dess.
For example, the team has found that disease transmission isn’t as simple as a big road bringing people who carry diseases from cities to the country. Instead, the researchers found that many pathogens are local to villages. Levy gave the example of a woman washing her child’s diaper in a river; those microbes don’t always travel downriver, but are usually caught in an eddy and remain in the local water supply.
Despite that, the remote villages with the strongest social networks are usually less at risk for infection than the villages close to the highway, which are usually home to a migrant population.
“Just think about a cohesive group that lives a long time in a certain community and with each other,” said Eisenberg. “They’re more organized. They’re more likely to build their houses in a structured way in which the waste water [drains away from residential areas]. If you’re a living in a community on the road, where no one really knows each other, they’re building houses haphazardly … you’re going to wind up with the worst conditions for water and sanitation.”
That said, often travelers on the road do bring in new pathogens to rural areas that have never had to cope with that kind of disease.
This phase of the project hopes to glean information specific to Zika and Dengue; how mosquitoes are spreading the disease, how humans help mosquitoes flourish, and how social networks might play a role in the transmission and prevention of both diseases.
Students at all six schools – University of Michigan, Trinity College, UC Berkeley, Emory University, Universidad San Francisco de Quito,and Universidad Central del Ecuador – have played a big role in the Eco Dess project in the last 15 years and will participate in the research funded by this grant as well, with students on campus doing literature reviews, coding research fieldnotes, and discussing project details.
A few students will travel to Ecuador, where they will participate in field research, observing how human behavior relates to Dengue and Zika transmission, talking with local residents about how they understand the diseases and what to do about them, and assisting with surveys.
Some of those students have stayed on. Levy, for example, got involved with Eco Dess as a graduate student at Berkeley.
It’s a valuable experience for those students – the program is an unusual example of a research project that has concentrated on one population over a long period of time.
“We really do understand what’s happening in a deeper way, and in a more sophisticated way, because we really understand these communities and know what’s happened over time,” Eisenberg said. “That’s been very satisfying.”