Human pathogen can cause coral disease

Despite the resilience of corals as a taxonomic group through geologic time, warming oceans, shifting seawater chemistry, overfishing, pollution, and disease currently threaten these habitat-building invertebrates with many coral reef ecosystems in a state of decline.  Researchers have identified a bacterium, Serratia marcescens as the cause of a disease called white pox in elkhorn coral (Acropora palmata).  White pox, more formally known as acroporid serratiosis, can lead to tissue loss and potentially the death of the coral colony.  What makes this especially interesting is that S. marcescens normally causes health troubles in humans–this is the first evidence of a human pathogen to a marine invertebrate.  Acropora palmata was once the dominant coral in the Caribbean, especially in the forereef and reef crest, shallow spots with high wave action.  Today, populations of this coral species has been decimated, reduced by up to 95% in abundance since 1980, and is now considered critically endangered by the IUCN.  Much of this decline is attributable to disease, along with other factors that compound this plight–for example, this species is particularly vulnerable to bleaching.

Previous work done in 2003 noted that S. marcescens was found in both untreated human waster and within A. palmata suffering from white pox, suggesting a relationship between the two.  In a new paper published this week in PLoS ONE, Dr Katheryn Sutherland and colleagues used Koch’s postulates, a standard method for showing disease causation, to  investigate the relationship between the two.  In short, fulfilling these postulates requires researchers to be able to isolate the suspected pathogen (S. marcescens) from the host coral and grown up in culture, the disease to manifest itself when a pure culture of the pathogen is introduced to the host, and isolated yet again from the experimentally-infected host (more on Koch’s postulates here).  The results show that S. marcescens is capable of causing white pox in this coral species speedily, with the coral losing tissue in as little as four days (see figure below).

While this disease is specific to this particular coral, the researchers also found that other coral species could possibly be acting as reservoirs for this pathogen while in seawater, given that the pathogen itself is not adapted well for life in the ocean.  Additionally, a coral predator, a snail, may act as a disease vector or reserve.

Improving wastewater containment and treatment in areas such as the Florida Keys can reduce this pathogen’s transmission, and efforts are ongoing in Florida to improve wastewater management, though this issue is occurring in the wider Caribbean as well.  This study shows an exception to the usual animal-to-human transmission model, but also that this pathogen, found in land-based mammals (us), can cause a disease in a marine invertebrate, jumping not only into a profoundly different environment but also into a much different animal, a colonial invertebrate rather than a vertebrate.  Responding to this issue would be obviously beneficial to corals themselves, but also to human health and for the economies that depend on reef habitats for tourism and resources.  The dynamics of this disease are yet another example that illustrate the interconnectivity of society, ecosystems, and economics.

 Figure:  Sutherland et al. 2011 (CC 2.5)

Sutherland, K., Shaban, S., Joyner, J., Porter, J., & Lipp, E. (2011). Human Pathogen Shown to Cause Disease in the Threatened Eklhorn Coral Acropora palmata PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023468

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4 thoughts on “Human pathogen can cause coral disease

  1. Perhaps I’m missing it, but I can’t seem to find attribution of any sort on the photo you are using in this post. As a public educator, I like to share my work via a Creative Commons license. If you reference the original work here: http://www.flickr.com/photos/nashworld/5645320766/in/set-72157626431694141 you’ll see that the license asks for “attribution,” share-alike,” and “non-commercial.”

    The main problem I have is that not only is this image not attributed for proper authorship, it also breaks the “share-alike” issue. You explicitly claim an “all rights reserved” license for all of the content on your blog. “Share-alike” means that you cannot use this content in a blog that is also not shared via a CC license. You cannot claim all rights reserved on something you have no rights to in the first place. I respectfully request your removal of this image from the site, or a discussion of compensation for the imagery used.

    Sean Nash

  2. Hi Sean,

    I’m glad that you saw that I did indeed give credit for your image. Additionally, the Creative Commons license that you use (http://creativecommons.org/licenses/by-nc-sa/2.0/) does have a ‘share-alike’ policy, which states: “Share Alike — If you alter, transform, or build upon this work, you may distribute the resulting work only under the same or similar license to this one.” I have not changed your image in any way, and thus from my reading of this, it does not seem that my site must match your CC license.

    A further note, my copyright page simply claims rights reserved for text and original images, while stating that images and figures not created by me will be properly attributed. I am certainly not claiming rights to your image.

    That being said, it is your image. I’ve removed it in order to clear the air of any misunderstanding that we may still have.

    cheers,
    Dusty

  3. Perhaps this arose from the footer at the bottom of the page discouraging publication without permission and stating a copyright (implicitly for original work, because if I give attribution for an image, I clearly am not claiming any rights to it). I’ve updated the wording a bit and linked to a page that more thoroughly explains it.

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