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Bats, Ebola, and Infectious Disease

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Bats, Ebola, and Infectious Disease

Last updated on October 17, 2014
Published on September 23, 2014
Written by Admin


The outbreak of Ebola in West Africa is a still-accelerating human tragedy in a region beset with limited capacity to curtail the disease.  As of October 8, 2014, more than 8,400 people in Guinea, Liberia, Nigeria, Senegal, Sierra Leone, Spain, and the United Sates had contracted Ebola since March, according to the World Health Organization (WHO), making this the largest outbreak on record since Ebola was first identified in Central Africa in 1976.  At least 4,033 people had died.  The fragile health-care systems in several of these countries have been overwhelmed, and many health care workers were among the earliest casualties.  WHO estimates that the number of people infected may rise to more than 20,000 by early November, with mortality approaching 70 percent.

Following the “requisite 42 days with active surveillance for new cases in place and none being detected,” WHO expects to declare the outbreak of Ebola virus disease over in Senegal on October 17 and over in Nigeria on October 20.

The infectious strain of Ebola causing the epidemic in West Africa appears to be Zaire ebolavirus.  If so, determining how the disease jumped from Central Africa to West Africa is a question to which scientists may never have a definitive answer.  Infectious disease experts believe that fruit bats may be a natural reservoir for Ebola and can infect other animals, including humans, livestock and primates, through their droppings or half-eaten fruit, or from direct exposure to the blood or other bodily fluids of diseased bats.  Whether fruit bats carrying Zaire ebolavirus made the 2,000-mile flight to West Africa is not known.  Some scientists believe the thriving underground importation of primates and bushmeat from Central Africa may be a more likely route of transmission.  An April paper in The New England Journal of Medicine suggests instead this may be a new strain closely related to Zaire ebolavirus that may have been present in West Africa for many years.

 

Whatever the cause of the current epidemic, conservationists and public health officials have worried for years about the human-caused disappearance of forests and other natural ecosystems, which brings (often poor) human populations into contact with wildlife that potentially harbor zoonotic (i. e., originate in wildlife) diseases that can jump to humans.  Those handling or eating killed bats, gorillas, chimpanzees, bonobos and other primates put themselves at risk of contracting such diseases.  The Guinea government banned eating bushmeat earlier this year, in fact, as the Ebola outbreak began to spread. 

Bat Conservation International’s core mission is “The Conservation of Bats and their Habitats Worldwide.”   BCI’s conservation actions fully embrace the “One Health” movement which recognizes that conservation biologists and public health officials confront the same ecological problems.  As stated in the executive summary of the “One Health” Initiative, “the convergence of people, animals, and our environment has created a new dynamic in which the health of each group is inextricably interconnected.”  

The common concerns for bat conservation and increasing exposure to emerging bat-borne diseases include: 1) habitat destruction; 2) human encroachment and contact with bats (including contact with livestock); 3) direct exploitation (hunting & eating with bushmeat markets as mixing pots for infectious diseases); 4) climate change (range expansion of pathogens and hosts, extreme events like floods, droughts, storms, disruption of community and ecosystem function, food shortages, and stress); 5) introduced species (e.g. White-Nose Syndrome).  From this perspective, when it comes to emerging infectious diseases and their causes, bats are victims as well as vectors.   

As noted, over the last decade, increased surveillance and improved techniques for disease detection have implicated bats as reservoirs and likely vectors for a lengthening list of pathogens that can affect humans and domestic animals.  These include Marburg, Nipah, Hendra, SARS-like coronaviruses, flu virus, a panoply of lyssaviruses including rabies, and most notably, Ebola.  Research has also revealed that more than 60 percent of all emerging infectious diseases are zoonotic, and that bats are not exceptional among wildlife as potential sources of human disease.  The causes for the emergence of these diseases from wildlife into human populations are fundamentally ecological, resulting from the disruption of our natural habitats, and are inevitably exacerbated by social disorder and political instability.

At the same time, bats are critical to the health of ecosystems worldwide.  Their profound impact on insect control is well known.  Bats are also essential pollinators for hundreds of plant species, many of which are food crops.  And studies have shown that a majority of the pioneer plants in a regenerating area of rainforest are species whose fruits are eaten and seeds spread across the landscape by fruit bats.

As the world’s leading organization for the conservation of bats, BCI must ensure that bat conservation is fully integrated into the best possible actions for public health and safety.  When public health and the interests of conservation appear to conflict, immediate concerns for public health will inevitably trump conservation and its multiple long-term benefits.  But such apparent conflicts, in BCI’s view as a science-based organization, are indeed “apparent” and usually preventable.

Conservation and disease management are complementary and function best when based on sound scientific knowledge.  When the current Ebola epidemic is contained and the prevention of future outbreaks is discussed, BCI and our partners will do our best to prevent the pointless persecution of bats in West Africa and advocate for the adoption of One Health principles that safeguard habitat for bats and other wildlife and put an end to eating bats and primates and the illegal wildlife trade in bushmeat and live primates.

In the meantime, our hearts go out to the people of West Africa, for the enormous suffering being caused by the present Ebola epidemic.  BCI and its public health partners will do all we can to fill critical gaps in our understanding of the cause of the current outbreak and convince governments in West Africa to implement effective One Health practices that minimize the chance for future Ebola epidemics.

How You Can Help

Doctors Without Borders was one of the first organizations to respond to the Ebola crisis in West Africa, and it remains at the forefront of efforts to treat infected individuals.  You can make a donation to the organization at www.doctorswithoutborders.org

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