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Vectorborne and Zoonotic Diseases & Climate Change

 
Global Environmental Health

Vectorborne and zoonotic diseases (VBZD) are infectious diseases whose transmission involves animal hosts or vectors.  Vectorborne diseases, such as malaria, are those in which an organism, typically insects, ticks, or mites, carry a pathogen from one host to another, generally with increased harmfulness (virulence) of the pathogen in the vector. Zoonoses, such as Avian Flu, are diseases that can be transmitted from animals to humans by either contact with the animals or through vectors that carry zoonotic pathogens to from animals to humans.  While many VBZD, such as malaria, yellow fever, dengue, and murine typhus, are rarely seen in the United States, we are directly susceptible to VBZD that are found in warmer climates and vulnerable due to global trade and travel.  Many VBZD are climate sensitive and ecological shifts associated with climate change are expected to impact the distribution and incidences of these diseases.

 

Doctor examining man with disease boils on his back

 

Health Impacts

  • Changes in temperature and precipitation directly affect VBZD through pathogen-host interaction, and indirectly through ecosystem changes and species composition.
  • As temperatures increases vectors can spread into new areas that were previously too cold. For example, two mosquito vectors that carry malaria are now found at the U.S.-Mexico border.
  • Change in incubation period of pathogens in invertebrate vectors due to precipitation and temperature can alter transmission.   For instance, an increase in temperatures and precipitation can increase the population of vectors where they normally live. More frequent droughts in some areas can cause a decrease in vectors that require water for their lifecycle.
  • Disruption and movement of human population can expand distribution of pathogens and increase exposure routes.
  • A decline in biodiversity alters predator-prey relationships.  A decline in the predators of vectors can increase vector populations.

 

Mitigation and Adaptation

  • Reducing greenhouse gas emissions to influence local ecological environment, thereby altering the life cycles of certain disease vectors and animals 
  • Preserving forests and wetlands to affect ecology and transmission cycles 
  • Developing and implementing early warning systems to reduce exposure to environmental hazards and limit susceptibility in exposed populations 
  • Encouraging air conditioning use against extreme heat and providing a co-benefit of reduced exposure to VBZD
  • Capturing and storing water runoff that can provide a breeding habitat for mosquitoes and increase the incidence of West Nile virus and other VBZD

 

Research Needs

  • Developing new pesticides aimed at controlling disease vectors that combine the qualities of:
    • specificity (affecting only the target arthropods)
    • adjustable persistence through formulation (chemically labile but persistent for useful periods)
    • environmental safety (no bioaccumulation or effect on non-target organisms)
    • low susceptibility to resistance (through either inherent physiology or effective resistance management techniques)
    • application to creative control strategies

 For more information, please visit the chapter on Vectorborne and Zoonotic Diseases in A Human Health Perspective on Climate Change (Full Report)(4MB) .

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