Study links disease, poverty and biodiversity
Poverty and disease often come together. That much is well
understood. But how much does poverty foster disease? Or, how much can
disease perpetuate poverty? And what's the role of nature, given that so
many infectious diseases are spread by mosquitoes or spend part of their
life cycle outside of the human body?
A new study finds that certain types of infectious and parasitic
diseases have a significant influence on economic development across the
world and accounts for some of the differences in per capita income
between those who live in countries in the tropics or those in temperate
latitudes. And the team of economists and ecologists suggests that
healthy forests or other ecosystems, with broad diversity of plants and
animals, can ease the burden of parasitic diseases and those spread by
mosquitoes or other vectors.
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Mosquitoes are major
vectors of diseases in the tropics. |
The authors, writing in the Public Library of Science Biology, make
these assertions based on an extensive analysis of data from the World
Bank on per capita income in 139 countries and the burden of parasitic
and vector-borne diseases as measured by lives lost as well as time lost
to illness.
Although many economists now recognise that malaria and hookworm can
hamper economic growth, the authors write, "an intense debate remains on
the relative importance of general disease burden on global patterns of
wealth and poverty." Many of the extremely poor live in the tropics, the
latitudes that tend to harbour more infectious diseases.
The study, led by Matthew H. Bonds, an economist and ecologist at
Harvard Medical School's department of global health and social
medicine, wanted to look beyond how the differences in latitudes
correlate with disease and poverty. They also wanted to control for
other economic influences, such as well-functioning government, legal
and economic institutions.
Disentangling cause and effect can be tricky, and the authors used a
statistical approach to evaluate the relative importance of various
causal factors, while controlling for variables.
"Our model indicates that vector-borne and parasitic diseases (VBPDs)
have systematically affected economic development," the authors write.
"Importantly, we show that the burden of VBPDs is, in turn, determined
by underlying ecological conditions. In particular, the model predicts
that the burden of disease will rise as biodiversity falls." The study
explains that some diseases, such as Lyme disease and malaria, rely on
other hosts for part of their life cycle and can increase as these
non-human hosts multiply with the loss of predators and competitors. For
example, rodent populations soar when coyotes, wolves, owls or other
predators aren't around to eat them.
"Our study shows that biodiversity also seems important in boosting
economic welfare - probably through its impact on buffering disease
outbreaks," said Andrew P. Dobson, a co-author who studies infectious
diseases at Princeton University's department of ecology and
evolutionary biology.
- Los Angeles Times
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