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<h5 class="section-title" id="d4721846e157">Background</h5>
<p dir="auto" id="P3">Environmental degradation facilitates the emergence of vector-borne
diseases, such
as malaria, through changes in the ecological landscape that increase human–vector
contacts and that expand vector habitats. However, the modifying effects of environmental
degradation on climate–disease relationships have not been well explored. Here, we
investigate the rapid re-emergence of malaria in a transmission hotspot in southern
Venezuela and explore the synergistic effects of environmental degradation, specifically
gold-mining activity, and climate variation.
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<h5 class="section-title" id="d4721846e162">Methods</h5>
<p dir="auto" id="P4">In this spatiotemporal modelling study of the 46 parishes of
the state of Bolívar,
southeast Venezuela, we used data from the Venezuelan Ministry of Health including
population data and monthly cases of
<i>Plasmodium falciparum</i> malaria and
<i>Plasmodium vivax</i> malaria between 1996 and 2016. We estimated mean precipitation
and temperature using
the ERA5-Land dataset and used monthly anomalies in sea-surface temperature as an
indicator of El Niño events between 1996 and 2016. The location of suspected mining
sites in Bolívar in 2009, 2017, and 2018 were sourced from the Amazon Geo-Referenced
Socio-Environmental Information Network. We estimated measures of cumulative forest
loss and urban development by km
<sup>2</sup> using annual land cover maps from the European Space Agency Climate Change
Initiative
between 1996 and 2016. We modelled monthly cases of
<i>P falciparum</i> and
<i>P vivax</i> malaria using a Bayesian hierarchical mixed model framework. We quantified
the variation
explained by mining activity before exploring the modifying effects of environmental
degradation on climate–malaria relationships.
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<h5 class="section-title" id="d4721846e182">Findings</h5>
<p dir="auto" id="P5">We observed a 27% reduction in the additional unexplained spatial
variation in incidence
of
<i>P falciparum</i> malaria and a 23% reduction in
<i>P vivax</i> malaria when mining was included in our models. The effect of temperature
on malaria
was greater in high mining areas than low mining areas, and the
<i>P falciparum</i> malaria effect size at temperatures of 26·5°C (2·4 cases per 1000
people [95% CI
1·78–3·06]) was twice as high as the effect in low mining areas (1 case per 1000 people
[0·68–1·49]).
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<h5 class="section-title" id="d4721846e196">Interpretation</h5>
<p dir="auto" id="P6">We show that mining activity in southern Venezuela is associated
with hotspots of
malaria transmission. Increased temperatures exacerbated malaria transmission in mining
areas, highlighting the need to consider how environmental degradation modulates climate
effect on disease risk, which is especially important in areas subjected to rapidly
rising temperatures and land-use change globally. Our findings have implications for
the progress towards malaria elimination in the Latin American region. Our findings
are also important for effectively targeting timely treatment programmes and vector-control
activities in mining areas with high rates of malaria transmission.
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<h5 class="section-title" id="d4721846e201">Funding</h5>
<p dir="auto" id="P7">Biotechnology and Biological Sciences Research Council, Royal
Society, US National
Institutes of Health, and Global Challenges Research Fund.
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