The Role of Climate Change The Role of Climate Change in Spreading Diseasein Spreading Disease

Marie PizzornoMarie Pizzorno

Dept. of BiologyDept. of Biology

Cell Biology/Biochemistry ProgramCell Biology/Biochemistry Program

Possible Effects of Climate ChangePossible Effects of Climate Change

Altered/increased ranges of insects and Altered/increased ranges of insects and animals that transmit diseasesanimals that transmit diseases

Change of seasonal infections – like Change of seasonal infections – like influenza – to year round infectionsinfluenza – to year round infections

Increase in extreme weather events that Increase in extreme weather events that exacerbate availability of clean waterexacerbate availability of clean water

Indirect effects of loss of agricultural land Indirect effects of loss of agricultural land and rainforests due to drought or flooding.and rainforests due to drought or flooding.

Vector-Borne InfectionsVector-Borne Infections

Any infectious agent that uses an insect or Any infectious agent that uses an insect or animal to be transmitted to its hosts.animal to be transmitted to its hosts.

Malaria (single-celled parasite, mosquito)Malaria (single-celled parasite, mosquito) Viruses transmitted by insectsViruses transmitted by insects Viruses transmitted by rodentsViruses transmitted by rodents Bacterial diseases transmitted by insects Bacterial diseases transmitted by insects

or animalsor animals

Climate Change and MosquitoesClimate Change and Mosquitoes

Warming of the environment –Warming of the environment – Increases the viable range of mosquitoes into Increases the viable range of mosquitoes into

higher elevations and latitudeshigher elevations and latitudes Boosts their rates of reproduction and the Boosts their rates of reproduction and the

number of blood meals they takenumber of blood meals they take Prolongs their breeding seasonProlongs their breeding season Shortens the maturation period for the Shortens the maturation period for the

microbes their transmitmicrobes their transmit

Migration of Migration of MosquitoesMosquitoes

•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 - MalariaIncreased Range - Malaria

Predicted Increase in Malaria Predicted Increase in Malaria TransmissionTransmission

Epstein P.R., Scientific American, Aug. 2000, pp50-57.

HantavirusHantavirus Emerged as a new disease in Emerged as a new disease in

the southwest US in 1993the southwest US in 1993 Drought followed by heavy rains led to an Drought followed by heavy rains led to an

increase in the deer mouse population increase in the deer mouse population (related to El Ni(related to El Niñño event)o event)

Increased contact with mice transmitted the Increased contact with mice transmitted the previously unrecognized virus to humans.previously unrecognized virus to humans.

Caused outbreak of Hantavirus Pulmonary Caused outbreak of Hantavirus Pulmonary Syndrome (32 deaths, 53 total infections)Syndrome (32 deaths, 53 total infections)

Total US cases = 465 (fatality 35%)Total US cases = 465 (fatality 35%)

Deer Mouse

Spread of HPS in USSpread of HPS in US

West Nile VirusWest Nile Virus

Transmitted by infected mosquitoes to Transmitted by infected mosquitoes to birds and humansbirds and humans

First appeared in NY state in 1999First appeared in NY state in 1999 Infected healthy adults may show no Infected healthy adults may show no

symptoms or may have a moderately symptoms or may have a moderately severe flu-like illness.severe flu-like illness.

Can cause encephalitis/meningitis in older Can cause encephalitis/meningitis in older adults with neurological complications.adults with neurological complications.

West Nile VirusWest Nile Virus

Mild winter 1998-1999 and an early spring Mild winter 1998-1999 and an early spring enabled mosquitoes to survive. enabled mosquitoes to survive.

Drought in spring/summer killed off Drought in spring/summer killed off mosquito predators.mosquito predators.

Heat wave allowed virus to mature faster.Heat wave allowed virus to mature faster. Increased infection of birds and Increased infection of birds and

mosquitoes mosquitoes human infections. human infections. Torrential rains in August increased pools Torrential rains in August increased pools

of water for mosquito breeding.of water for mosquito breeding.

West Nile Virus - DistributionWest Nile Virus - Distribution

1999

2007

Dengue Fever VirusDengue Fever Virus

Carried by the Carried by the Aedes aegyptiAedes aegypti mosquito. mosquito. First infection with one of the four strains First infection with one of the four strains

of DFV causes a debilitating flu-like illness of DFV causes a debilitating flu-like illness that is usually not fatal.that is usually not fatal.

Second infection with a different strain of Second infection with a different strain of the virus leads to a hemorrhagic fever with the virus leads to a hemorrhagic fever with a mortality of 30%.a mortality of 30%.

The The Aedes aegyptiAedes aegypti is expanding its range is expanding its range and has moved into the southern US.and has moved into the southern US.

Dengue VirusDengue Virus

Other Health ConcernsOther Health Concerns

Lyme Disease – caused by a bacterium that is Lyme Disease – caused by a bacterium that is transmitted by ticks.transmitted by ticks.

Cholera – a water-borne bacterial disease that Cholera – a water-borne bacterial disease that increases after severe flooding.increases after severe flooding.

Animal and plant diseases – affecting Animal and plant diseases – affecting agricultural productivity.agricultural productivity.

Non-infectious diseases – such as allergies and Non-infectious diseases – such as allergies and asthma - may also be connected to increasing asthma - may also be connected to increasing COCO22 levels and climate change levels and climate change

ConclusionsConclusions While it may be difficult to predict the actual While it may be difficult to predict the actual

effect that global warming will have on the effect that global warming will have on the incidence and location of disease, it is obvious incidence and location of disease, it is obvious that the ecological changes that will result from that the ecological changes that will result from global climate change will affect the distribution global climate change will affect the distribution and frequency of many disease causing agents and frequency of many disease causing agents and their vectors.and their vectors.

See work by Paul R. Epstein at the Harvard See work by Paul R. Epstein at the Harvard Center for Health and the Global Environment Center for Health and the Global Environment http://chge.med.harvard.edu/about/faculty/epstein.htmlhttp://chge.med.harvard.edu/about/faculty/epstein.html