Protecting the landscape may also help protect people from some infectious diseases, according to Erica Smithwick, associate professor of geography. Smithwick and her colleagues have been investigating how land use has affected the spread of two diseases in sub-Saharan Africa.
They have found that areas with more landscape edges—where different ecosystems meet—correlate with increased spread of disease. Researchers have observed a similar phenomenon in the U.S., where ticks carrying the Lyme disease parasite attach themselves to deer and mice that feed at the edges of forests, and are then carried by their hosts to new areas they could not have reached on their own. More edges means more hosts, and researchers have shown that this leads to increased incidence of Lyme disease.
Smithwick says the same may be true for two diseases that are common in Africa, malaria and Buruli ulcer.
In terms of infections, Buruli ulcer is fairly new. Reports of skin ulcers in sub-Saharan Africa date back to the early 1900s, but it wasn’t until the 1990s that the disease became more prevalent. In 1998, the World Health Organization (WHO) launched a Global Buruli Ulcer Initiative to focus more resources on treating the debilitating disease.
It is caused by a water-borne bacterium, but the exact means of transmission is not yet known; it may be carried by an aquatic insect or may enter breaks in the skin directly from contaminated water. The disease leaves skin lesions and scars on affected individuals, typically on arms, legs and hands. It’s treatable with antibiotics, but if it’s not addressed early it can cause long-term disabilities.
“Buruli ulcer is a disease of low-income populations, and it has affected rural parts of Ghana the most,” says Smithwick. “It causes physical scarring and deformities on the skin, so there are stigmas associated with it. Sometimes people with the ulcer are ostracized. Without knowing the cause of the disease, it’s unlikely that someone would seek treatment for it.”
As of 2016, there are no reliable preventive measures for Buruli ulcer, according to WHO. Knowing this, Smithwick and her team sought to understand the social and environmental factors that influence how the disease spreads.