What doesn’t kill you makes you stronger

The 2014 Ebola epidemic was the largest known outbreak of Ebola in history, notably affecting multiple countries in West Africa as well as across the world. According to the Center for Disease Control (CDC), as of September 2015, there are 17,548 confirmed cases in Sierra Leone and Guinea alone. Four cases, with one death, were reported in the United States, leading to a massive worldwide panic.

Map describing spread, extent and severity of Ebola virus across the world in 2014. It is apparent that the 2014 Ebola epidemic had its roots in western Africa, specifically in Sierra Leone and Guinea, and spread across the world. Source: http://www.cnn.com/2014/10/06/health/ebola-us/

Map describing spread, extent and severity of Ebola virus across the world in 2014. It is apparent that the 2014 Ebola epidemic had its roots in western Africa, specifically in Sierra Leone and Guinea, and spread across the world.
Source: http://www.cnn.com/2014/10/06/health/ebola-us/

While the Ebola parasite caused disastrous effects for its animal hosts, all parasites, including Ebola, play a very unique and important role in host life cycles. It is important to not diminish their importance in the ecosystem as they help maintain ecosystem stability and facilitate interactions between species.

According to a recent article in the Journal of Biogeography, researchers from Duke University and University of New Hampshire have shown that parasite richness and prevalence is due to a combination of factors including time since introduction, method of introduction and host availability.

In this article, Blakeslee et al. showed that organisms have the ability to lose parasites over their evolutionary history. Even after controlling for differences in acquisition of samples, the number and prevalence of parasites differed significantly, suggesting that host invasion history and parasite life history plays a key role in the diversity of parasites transferred to the host population. These effects compound with time.

Why is this a good thing? This influential study suggests that host invasion history is influenced by its corresponding parasite life history. We could have guessed that this would be the case as one population directly depends on the other for survival.

But this study goes a step further and characterizes the role of parasites in every day life. It shows that the diversity and expansion of parasites are indicative of and transferred to their host populations. This means that we can, knowing the diversity of parasite populations, we can understand and predict the community influence of parasites on their host populations.

So what does this mean to us really? On a surface level, we thought that parasites play only a superficial role in our global ecosystem. Really, they seem to only cause harm by killing and seriously injuring of our valued organisms. The world (or at least the human race) would feel a lot safer of parasites were eliminated entirely. We could finally win the genetic fight against the microscopic organisms that have literally plagued us from the start of human evolution.

But if we dig deeper, we see that parasites actually play a significant role in determining host concentrations and are indicative of host availability. For example, according to researchers from the Hungarian Natural History Museum, conservation of parasitic lice has led to increased conservation of host species. Contrary to popular belief, Dr. Rozsa believes this natural culling actually occurs because it ensures genetic diversity within the host population and promotes healthy and natural competition between the two populations. Mind blowing, right?

When we really get down to it, the differences between parasite-host and predator-prey interactions are slim. If this is the case, why do conservationists insist on killing out a parasite from the ecosystem when we work tremendously hard to maintain healthy predator relationships within every ecosystem? If we stop and think about it, selectively removing parasites from our environment will cause a greater causality in the future.

While conventional conservation efforts often work to save large animals, we have to stop and wonder if we are doing more harm than good. If every organism were as equally as valuable as the next, wouldn’t it make more sense to conserve parasites as well as their hosts?

By no means are we suggesting that we stop vaccinating our children and trying to treat parasitic infections. All we are saying is that while parasites pose a health risk to organisms, they are crucial elements of our environment and we should act cautiously before eradicating them from our world entirely. We never know about the true long-term effects of removing an entire species from existence until it actually happens.

According to Dr. Tom Frieden, the Director of the CDC, Ebola was never a concern for America. “The bottom line here is that I have no doubt that we will control this importation or this case of Ebola so that it does not spread widely throughout this country,” said Dr. Frieden.

And I believe him. A parasitic invasion should not be a death sentence. Rather, we should work with our organisms to build a healthier world. Focusing on parasite conservation will not cause the extinction of the human race; rather, it will build healthy competition and allow us to study host populations with greater accuracy.

 

References

Blakeslee, April M. H., Irit Altman, A. Whitman Miller, James E. Byers, Caitlin E. Hamer, and Gregory Ruiz. “Parasites and Invasions: A Biogeographic Examination of Parasites and Hosts in Native and Introduced Ranges.” Journal of Biogeography39.3 (2011): 609-22.

Brumfield, Ben, and Josh Levs. “1st Case of Contracting Ebola outside of Africa – CNN.com.” CNN. Cable News Network, 6 Oct. 2014. Web. 22 Oct. 2015. <http://www.cnn.com/2014/10/06/health/ebola-us/&gt;.

Rózsa L, Vas Z. 2015. Co-extinct and critically co-endangered species of parasitic lice, and conservation-induced extinction: Should lice be reintroduced to their hosts? Oryx 49.1 (2015):107-110.

USA. Centers for Disease Control. Centers for Disease Control and Prevention. By Tom Frieden, David Lakey, Edward Goodman, and Zachary Thompson. Centers for Disease Control and Prevention, Published: 30 Sept. 2014. Web. Accessed: 22 Oct. 2015. <http://www.cdc.gov/media/releases/2014/t0930-ebola-confirmed-case.html&gt;.

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