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December 7, 2017

Sharing isn’t always polite, judging by this EarthWord. 

EarthWords is an on-going series in which we shed some light on the complicated, often difficult-to-pronounce language of science. Think of us as your terminology tour-guides, and meet us back here every week for a new word!


The EarthWord: Zoonotic

Blacklegged Ticks are Lyme Disease Carriers
Black-legged ticks can spread Lyme disease, which is zoonotic. (Credit: Graham Hickling, University of Tennessee)


  • We share many things with our animal friends, like habitats, resources, and even genes. But contrary to what you learned in preschool, sharing is not always polite. Zoonotic diseases or infections are those that spread between animals and humans, such as Lyme disease, some strains of  highly pathogenic avian flu, rabies, and plague.
  • Zoonotic illnesses range from mild to severe and, in extreme circumstances, can be deadly to animals, humans, or both.
  • Seven of 10 zoonotic diseases originate in wildlife.


  • The word zoonotic, or zoonosis, stems from the Greek words zoion, which means animal, and nosis, which means disease.

Use/Significance in the Earth Science Community:

  • According to the Centers for Disease Control and Prevention, anyone can become sick from zoonotic diseases, but children, seniors, and people with weakened immune systems are most at risk.
  • Zoonotic diseases negatively affect already threatened or endangered wildlife species, and their impacts ripple throughout ecosystems. For example, sylvatic plague, a bacterial disease spread by fleas, has decimated prairie dog colonies throughout the western United States. Endangered black-footed ferrets rely on prairie dogs as their main food source, and are also susceptible to the disease.



Hungry for some science, but you don’t have time for a full-course research plate? Then check out USGS Science Snippets, our snack-sized science series that focuses on the fun, weird, and fascinating stories of USGS science.

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