Bats out of hell: Increasing risk of new infectious diseases | Biology
Two-year-old Emile Ouamouno and friends often played in and around a large, hollow tree 50 yards from his home.
They played with the free-tailed bats roosting there. Some kids caught bats for food. Others just played near the tree likely contacting bat feces and body fluids.
Emile became seriously ill in early December 2013. He died on Dec. 5 of that year and became “patient zero” for the 2014-2016 West African outbreak of Ebola, one of the most-lethal viruses known.
Eventually that outbreak infected 28,652 people; 11,325 died.
Scientists discovered the Ebola virus in 1976. It infected, but did not always kill, native mammal species in Zaire (Democratic Republic of Congo), near the Ebola River. Obviously, Ebola can “spillover” from native hosts to humans.
Seventy-five percent of new and emerging infectious diseases in humans “jumped” from other animals, especially fellow mammals with which we are most-related and physiologically similar. Our infectious diseases can spillover to other animals, especially mammals, as well.
The SARS-CoV-2 virus that causes COVID-19, ‘spilled over’ from other mammals, likely bats, to humans in the last several years. So did SARS-CoV-1 in 2003, Middle East Respiratory Syndrome (MERS) in 2013, HIV/AIDS, West Nile, Monkeypox, and Lyme disease.
The world’s human population has more than tripled over the last 70 years to its current, and still growing, 7.9 billion people. That alone makes humanity a growing target for infectious diseases under the constant pressure of natural selection.
This human population explosion caused and was supported by great changes in interactions with our environment. Clearing forests, converting grasslands to farmland, extracting coal and other fossil fuels led to displacement of native animal species. That led to greater opportunities to contact and jump to new and increasingly plentiful human hosts.
Human-caused warming and associated increases in rainfall has permitted range expansion of insects such as mosquitoes and ticks that carry numerous infectious diseases. In Ohio, tick populations and the diseases they carry are increasing.
Collin Carlson, a biologist at Georgetown University, and colleagues assembled data on ranges of 3,139 mammal species, especially bats; the viruses known to infect them; and predicted changes in ranges of those mammals due to global warming. They constructed a model of spillover possibilities under standard scenarios for climate change severity over the next 50 years.
In a peer-reviewed paper published three months ago in Nature, they predict a rise in mammalian spillover events due to warming-caused changes. Those changes will bring many mammal species into contact with each other for the first time. They predict 4,000 more spillover events as ranges of species they considered continue to respond to warming.
The research team called special attention to current range changes among bat populations in Southeast Asia and other regions. These regions support large, growing, human population centers facilitating spillover and spread of novel infectious diseases to humans.
They urge increased monitoring of potential candidates for spillover events in mammalian biodiversity hotspots that their analyses identified.
Absent such biological research, new infectious diseases will likely come at us like a bat out of hell.
Steve Rissing is professor emeritus in the Department of Evolution, Ecology, and Organismal Biology at Ohio State University.
steverissing@hotmail.com
This article originally appeared on The Columbus Dispatch: Climate change, rising populations could bring new infections
