Over the last few decades, we've realized that organisms are far more complicated than they initially appear. What may look like an individual fox is actually an ecosystem containing trillions of microorganisms on every square inch. [Figure 1]
Despite their tiny size, microbes influence important host functions, such as development, digestion, stress tolerance, behavior, and even immunity. Therefore learning more about these hidden actors can inform wildlife conservation of at-risk species in the modern molecular era.
|Looking into the ear canal of an island fox.
However, there's more to this story. We still don't fully understand how mite infection leads to tumor growth. In particular, my collaborators and I wondered whether microbes play a role in this system. For example, do mites disrupt healthy microbes and cause secondary bacterial infections? And do those infections then contribute to the chronic inflammation that precedes tumor growth?
|Figure 2: Island fox is swabbed during health check
The results came back loud and clear: microbes differed between mite-infected and uninfected ear canals. Rather than a rich community of diverse microbes (as seen in healthy ears), mite-infected ear canals had fewer microbial species present. We further found that the balance of microbes (know as "relative abundance") differed between infection groups. [Figure 3]
|Figure 3: Classes of bacteria found in swab samples
Even though this microbe is commonly found on canid species (such as domestic dogs and foxes), it can become an opportunistic pathogen when healthy communities are disrupted. Once it proliferates, it can be incredibly difficult for the immune system or even antibiotics to eradicate, leading to chronic inflammation.
We now hypothesize that mite infection and secondary bacterial infection with Staphylococcus pseudintermedius contribute to chronic inflammation and tumor growth in Santa Catalina Island foxes.
|Photo courtesy of Glenn Jensen
Alexandra DeCandia, Department of Ecology & Evolutionary Biology, Princeton University, Princeton, New Jersey.
Read the full paper: Ear mite infection is associated with altered microbial communities in genetically depauperate Santa Catalina Island foxes (Urocyon littoralis catalinae)
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