Tag Archives: Yellow Fever

Deforestation and Disease

Much attention is focused on the broader environmental and climatic consequences of deforestation, especially as this has seemed to pick up pace in places like the Amazon Basin. More attention is also needed concerning the disease transmission implications of deforestation. Recent studies have shed light on the problem. Basically deforestation as a result of urbanization or expanding commercial agriculture and related human activity brings people closer to areas where diseases can spread.

The connection between bats and the spread of Ebola in humans has been posited for some time. Forest News notes that “Fruit bats (Pteropodidae) are suspected reservoir hosts for the Ebola virus,” and thus, “Deforestation may accelerate the spread of the deadly Ebola disease in the rainforests of West and Central Africa by increasing human-bat interactions.” They are sharing information by Olivero and colleagues recently published in Mammal Review.

These researchers “show that the range of some fruit bat species is linked to human activities within the favourable areas for the Ebola virus. More specifically, the areas where human activities favour the presence of five fruit bat species overlap with the areas where EVD outbreaks in humans were themselves favoured by deforestation.” They have modeled and mapped an area in West and Central Africa based on climate, including annual temperature ranges, the presence of rainforest and mammal distribution to create an area known as “The Ebola Virus Area.”

Concerning malaria, research by Chua and colleagues in Malaysia found that, “contributes to a growing body of evidence implicating environmental changes due to deforestation, expansion of agricultural and farming areas, and development of human settlements near to forest fringes in the emergence of P. knowlesi in Sabah.” Their research is part of more than a dozen studies over the past nine years that links deforestation and greater interaction between humans and macaque monkeys, the normal victim of P. knowlesi. One of the earlier studies reports that, ” ongoing ecological changes resulting from deforestation, with an associated increase in the human population, could enable this pathogenic species of Plasmodium to switch to humans as the preferred host.”

Eliminating the mammal hosts of these diseases is not an option because as Olivero explained about bats, “The entire function and ecology of forests would be put at risk if these vital pollinators and seed dispersers are eliminated.”

Considering another tropical disease, Visser warns that, “Climate change, deforestation, urbanization, and increased population mobility have made the risk of large outbreaks of yellow fever more likely than ever.” The lesson from these experiences is not mainly that we need to increase coverage of proven preventive measures, but that we need broader change in our approaches and policies toward land use.