Despite increasing health control measures, parasitic and infectious diseases have been emerging and recurring in South-East Asia — which the study calls “a recognised hotspot for biodiversity” and “which is suffering from rapid and extensive erosion of that diversity”.
The two trends may be linked, finds the study published in PLOS One (25 February), saying that “that although biodiversity is a source of pathogens, well-preserved biodiversity could act an insurance against outbreaks”.
It investigated incidences of infectious disease outbreaks from 1950 to 2010 and their relationship to socio-economic factors such as population size, gross domestic product and public health expenditure, as well as geography, climate and biodiversity factors, such as bird and mammal species and forest cover.
The researchers from France, Malaysia, Singapore and Thailand report that an increase in human activities resulting from economic development leads to several regional environmental changes. These include altered land use, the distributions of domestic animals and wildlife, as well as increased international trade.
“Biodiversity changes that occur through the fragmentation and degradation of natural habitats, particularly forested areas, increase the proximity of wildlife to humans and their domestic animals,” says the study. “These result in increased health risks through the increased transmission of zoonotic diseases.”
The study says further that the number of zoonotic disease outbreaks is positively correlated with the number of threatened mammal and bird species while the number of vector-borne disease outbreaks is negatively correlated with forest cover, denoting “the potential role of biodiversity as a buffer of pathogen spread”.
“Impoverishment of biodiversity, which is evident not only in the decreasing number of species but also in landscape fragmentation and simplification, favour what we call the synanthropic species” says Serge Morand, the lead author of the study and a parasitology scientist with the French National Centre for Scientific Research.
“Examples of synanthropic species include the common rats, which are the reservoirs of many infectious diseases such as leptospirosis, scrub typhus and hantaviruses. They also include some mosquitoes such as the Aedes albopictus, which is a vector of dengue and Japanese encephalitis,” he says.
Angelina Galang, director of the Environmental Institute of Miriam College in the Philippines, agrees with the study’s findings that biodiversity is closely related to the incidence of infectious diseases.
“A country that has highly diverse bird and mammal species also likely harbours a high number of vectors and reservoirs, which are essential elements for transmitting infectious diseases,” says Galang.
“High biodiversity means high number of infectious diseases. But increasing biodiversity loss, on the other hand, leads to an increase of disease outbreaks,” Moran concludes.
Link to full study in PLOS One
This article has been produced by SciDev.Net's South-East Asia & Pacific desk.