Biodiversity Loss Can Increase Infectious Diseases in Humans

Queensland's Daintree Rainforest, said to be 135 million yeras old, containing more rare and endangered plant and animal species than any other area

Fifty years ago, improved public health measures, the development of antibiotics, better vaccines, insecticides and advancements in surveillance resulted in a decline of infectious disease. However, an upturn in infectious diseases around the world, both emergence and reemergence, has been apparent since the late twentieth century. This increase marks the fourth major alteration in human-microbe relationships since the introduction of agriculture over 10,000 years ago.

This “epidemiologic transition” has triggered the development of new infectious diseases. Approximately 30 new diseases have been identified and old diseases have reemerged with a vengeance, like tuberculosis, malaria and cholera. These new diseases include human immunodeficiency virus/acquired immune deficiency syndrome (AIDS), Legionnaires’ disease, bovine spongiform encephalopathy (BSE)/variant Creutzfeldt-Jakob disease (vCJD), hepatitis C, Nipah virus, new hemorrhagic fevers as well as severe acute respiratory syndrome (SARS) and avian influenza.

Various changes in human ecology have contributed to this new era of infectious disease:

∙ rural-to-urban migration resulting in high density peri-urban slums;
∙ increasing long-distance mobility and trade;
∙ the social disruption of war and conflict;
∙ changes in personal behavior; and,
∙ the use and misuse of medical technology (e.g. the creation of drug resistant microbes).

Weiss, R., McMichael, A.J., Social and Environmental Risk Factors In The Emergence of Infectious Disease, 10 Nature Med. Supp. 570 (December, 2004).

Recently, more attention has been paid to the role of human-induced global changes in the increase in infectious disease, including widespread forest clearance and climate change. In a newly released study, “Biodiversity Loss Affects Global Disease Ecology,” which will be appearing in the December 2009 issue of BioScience, the authors review and combine a broad group of studies addressing this issue and conclude that there is an association between the current epidemiologic transition and biodiversity change, decline and extinction. As reported in ScienceDaily

‘Habitat destruction and biodiversity loss,’ -- driven by the replacement of local species by exotic ones, deforestation, global transportation, encroaching cities, and other environmental changes – ‘can increase the incidence and distribution of infectious diseases in humans,’ write University of Vermont biologist Joe Roman, EPA scientist Montira Pongsiri, and seven co-authors in BioScience.

According to ScienceDaily, Roman explains that "people have been working on this in individual diseases but no one has put all the studies together to compare them."

In 2006, he and Pongsiri gathered a group of scientists and policy analysts with expertise in a range of the new diseases being observed -- including West Nile virus as well as malaria, the African parasitic disease schistosomiasis, hantavirus pulmonary syndrome, and several others. From that meeting, the forthcoming BioScience study developed.

'We've reviewed all those studies and show that emergence or reemergence of many diseases is related to loss of biodiversity,’ says Pongsiri. 'We've taken a broad look at this problem to say that it's not just case-study specific. Something is happening at a global scale.’

‘We're not saying that biodiversity loss is the primary driver for all of these emerging diseases,’ says Roman, ‘but it appears to be playing an important role.

'We're trying to make the case that all of these environmental changes we're making, because they are anthropogenic, can be managed, can be controlled,’ says Pongsiri. ‘We may be able to actually reduce or prevent these diseases by managing for biodiversity from the genetic level to the habitat level.’

This new study is part of growing body of work in an area being referred to as Eco-epidemiology. This relatively new field of study brings epidemiology and ecology together to examine the relationship between biodiversity and public health. Among other issues, Eco-epidemiologists examine disease prevention in terms of habitat structure, promoting genetic diversity in non-human species and the protection of animal predators as ecosystem regulators.