Download Aedes aegypti

The Role of Climate Change
in Spreading Disease
Marie Pizzorno
Dept. of Biology
Cell Biology/Biochemistry Program
Possible Effects of Climate Change
 Altered/increased
ranges of insects and
animals that transmit diseases
 Change of seasonal infections – like
influenza – to year round infections
 Increase in extreme weather events that
exacerbate availability of clean water
 Indirect effects of loss of agricultural land
and rainforests due to drought or flooding.
Vector-Borne Infections
 Any
infectious agent that uses an insect or
animal to be transmitted to its hosts.
 Malaria (single-celled parasite, mosquito)
 Viruses transmitted by insects
 Viruses transmitted by rodents
 Bacterial diseases transmitted by insects
or animals
Climate Change and Mosquitoes
 Warming




of the environment –
Increases the viable range of mosquitoes into
higher elevations and latitudes
Boosts their rates of reproduction and the
number of blood meals they take
Prolongs their breeding season
Shortens the maturation period for the
microbes their transmit
Migration of
Mosquitoes
•Increasing
temperatures allow
mosquitoes to survive
at higher elevations
•Evidence of that this
is currently
happening in some
areas
Epstein P.R., Scientific American,
Aug. 2000, pp50-57.
Increased Range - Malaria
Predicted Increase in Malaria
Transmission
Epstein P.R., Scientific American, Aug. 2000, pp50-57.
Hantavirus
 Emerged
as a new disease in
Deer Mouse
the southwest US in 1993
 Drought followed by heavy rains led to an
increase in the deer mouse population
(related to El Niño event)
 Increased contact with mice transmitted the
previously unrecognized virus to humans.
 Caused outbreak of Hantavirus Pulmonary
Syndrome (32 deaths, 53 total infections)
 Total US cases = 465 (fatality 35%)
Spread of HPS in US
West Nile Virus
 Transmitted
by infected mosquitoes to
birds and humans
 First appeared in NY state in 1999
 Infected healthy adults may show no
symptoms or may have a moderately
severe flu-like illness.
 Can cause encephalitis/meningitis in older
adults with neurological complications.
West Nile Virus
 Mild
winter 1998-1999 and an early spring
enabled mosquitoes to survive.
 Drought in spring/summer killed off
mosquito predators.
 Heat wave allowed virus to mature faster.
 Increased infection of birds and
mosquitoes  human infections.
 Torrential rains in August increased pools
of water for mosquito breeding.
West Nile Virus - Distribution
2007
1999
Dengue Fever Virus
 Carried
by the Aedes aegypti mosquito.
 First infection with one of the four strains
of DFV causes a debilitating flu-like illness
that is usually not fatal.
 Second infection with a different strain of
the virus leads to a hemorrhagic fever with
a mortality of 30%.
 The Aedes aegypti is expanding its range
and has moved into the southern US.
Dengue Virus
Other Health Concerns
Lyme Disease – caused by a bacterium that is
transmitted by ticks.
 Cholera – a water-borne bacterial disease that
increases after severe flooding.
 Animal and plant diseases – affecting
agricultural productivity.
 Non-infectious diseases – such as allergies and
asthma - may also be connected to increasing
CO2 levels and climate change

Conclusions

While it may be difficult to predict the actual
effect that global warming will have on the
incidence and location of disease, it is obvious
that the ecological changes that will result from
global climate change will affect the distribution
and frequency of many disease causing agents
and their vectors.
 See work by Paul R. Epstein at the Harvard
Center for Health and the Global Environment
http://chge.med.harvard.edu/about/faculty/epstein.html