Will Climatic and Physical Environment Change Affect Ebola Distribution?

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As health officials struggle to contain an outbreak of Ebola hemorrhagic fever that originated in Guinea, and has already spread to Liberia and Sierra Leone, renewed concern and anxiety has arisen regarding emerging infectious diseases. Caused by a virus genus in the family filoviridae, Ebola is a vector-borne disease with several species of fruit bats as the suspected (though unconfirmed and not necessarily only) hosts. Initial infection is believed to occur from bites, scratches, and even consumption of infected bats. Illness can result in high fever, diarrhea, vomiting, and internal and external bleeding (CDC, 2009). The virus spreads via exchange of bodily fluids and has a case fatality rate ranging from 25-90%. In this particular outbreak, Ebola currently has an estimated fatality rate of 62.5%.

Putting aside, for the moment, challenges relating to vector identification and disease control, an issue that also warrants discussion is the potential change in disease distribution range resulting from shifting conditions in the physical environment. Historically, Ebola crossover from the host vector to humans has occurred primarily in rural villages of Central and West Africa, close to tropical rainforests. In general, the view is that bats are very climate-sensitive animals, and small changes to the physical environment can reduce species richness and habitat range (Bilhin, Kesisoglu, & Rebelo, 2012). An idea that receives less attention, however, is the possibility for continued deforestation and habitat degradation to increase contact frequency, and therefore transmission potential, between infected hosts and susceptible human populations. Such mechanisms might include, for instance, the continued encroachment of remote African villages, population growth and movement within and between such villages, and increased travel distances of bats in search of food.

In short, changes to climatic and physical environment conditions can be expected to alter interactions between humans and bats in a variety of ways. Assuming that bats have been correctly identified as the primary host reservoir of Ebola virus, such changes may also influence virus transmission potential and occurrence. An official from Médecins Sans Frontières has already described the current Ebola outbreak as “unprecedented” with regard to the extent of its distribution, highlighting that increased chance and occurrence of crossover will in turn increase risk of epidemic or pandemic situations. This is an issue that to date has been understudied and requires further research. It is worth noting that bats have also been identified as host reservoirs of a variety of other potentially deadly emerging infectious diseases, including rabies, histoplasmosis, SARS, Nipah, Hendra, Marburg, and Lyssaviruses.

References

BBC News. (March 31, 20140. Ebola outbreak in Guinea unprecedented – MSF, BBC News. [online]. Available at <http://www.bbc.com/news/world-africa-26825869> [Accessed April 1, 2014].

Bilgin, R., Kesisoglu, A., & Rebelo, H. (2012). Distribution patterns of bats in the Eastern Mediterranean Region through a climate change perspective. Acta Chiropterologica, 14(2), 425-37.

Centers for Disease Control and Prevention (CDC). (2009). Ebola Hemorrhagic Fever Information Packet. Atlanta, GA: Centers for Disease Control and Prevention Special Pathogens Branch.

Lallanilla, M. (March 27, 2014). Bat soup blamed as deadly Ebola virus spreads. Livescience.com. [online]. Available at <http://www.cbsnews.com/news/bat-soup-blamed-as-deadly-ebola-virus-spreads/> [Accessed April 1, 2014].

Moisse, K. (March 31, 2014). Ebola Outbreak in Guinea Spreads to Liberia, Sierra Leone. ABC News. [online]. Available at <http://abcnews.go.com/blogs/health/2014/03/31/ebola-outbreak-in-guinea-spreads-to-liberia-sierra-leone/> [Accessed April 1, 2014].

World Health Organization (WHO). (2014). Ebola virus disease. [online]. Available at <http://www.who.int/mediacentre/factsheets/fs103/en/> [Accessed April 1, 2014].

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Patrick Saunders-Hastings

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