Deforestation May Make
Humans More Vulnerable
To Infection
ScienceDaily - A new
study suggests that
socioeconomic factors
best explain patterns of
the infectious disease
American Cutaneous
Leishmaniasis (ACL) in
Costa Rica.
Contrary to the
established belief that
deforestation reduces
the risk of infection,
the research shows that
deforestation may
actually make socially
marginalized human
populations more
vulnerable to infection.
"The classical idea has
been that people working
or living close to the
forest were at risk for
the disease, but that
view failed to consider
such factors as quality
of life and general
level of health," said
co-author Luis Fernando
Chaves of the University
of Michigan. "Contrary
to what was previously
believed, the more
forest you have, even in
a marginal population,
the more protected you
are against the
disease."
The researchers examined
county-level ACL case
data from 1996 through
2000 for Costa Rica, a
country in which
approximately 20,000
acres of land are
deforested annually to
make way for cattle
ranching and banana,
mango and citrus fruit
plantations. In addition
to examining such
factors as forest cover,
rainfall, elevation, and
percent of the
population living less
than five kilometers
from the forest edge,
the researchers also
incorporated an index of
social marginalization
into their analysis.
This index, which takes
into account income,
literacy, level of
education, average
distance to health
centers, health
insurance coverage and
other indicators of life
at the margins of
mainstream society,
provides a single
measure of quality of
life.
The researchers found a
strong geographic
overlap between disease
incidence and social
marginalization that was
not found between
disease incidence and
the other ecological
variables.
"When we looked just at
factors such as climate
and the physical
environment, we found no
specific patterns with
respect to the disease,"
Chaves said. "But when
we looked at the social
data, we found clear
patterns according to
marginality."
Putting everything
together, the
researchers discovered
that in fact there is a
relationship between ACL
and deforestation, but
it's not the simple,
"less forest, less
disease" relationship
that previously was
believed to exist.
Instead, there's a
complex connection with
El Niño Southern
Oscillation (ENSO), a
periodic
ocean-atmosphere
fluctuation in the
Pacific Ocean that is an
important cause of
inter-annual climate
variability around the
world and also
influences disease
cycles. In highly
deforested counties,
socially marginalized
human populations are
more vulnerable to
ENSO's effects, and
disease incidence
actually is higher, the
analysis suggests.
Dr. Chaves concluded
that the "study calls
for control efforts
targeted to socially
excluded populations and
for more localized
ecological studies of
transmission in vectors
and reservoirs in order
to understand the role
of biodiversity changes
in driving the emergence
of this disease."
The researchers are now
planning on conducting
similar analyses for
other diseases, such as
malaria, paying close
attention to how
climatic fluctuations,
ecological factors, and
patterns of biodiversity
relate to human disease
patterns |
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