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Ebola and biodiversity

Ranty IslamNovember 4, 2014

Most of the globe's biodiversity is invisible to the bare eye. Yet, microbes were vital in bringing about today's diversity of plants and animals. Even the deadly Ebola virus has its place in the grand scheme of things.

Electron microscope image of Ebola viruses on an infected cell
Image: Reuters/NIAID

Ebola does not seem to be something one would want to come face to face with. Yet, in Amsterdam's Plantage neighbourhood people are happy to do just that. And pay up to 14 euros for the pleasure. Locked away in the second of eight glass cabinets on the ground floor of a big black building, a large carefully crafted glass model of the deadly virus is one of the attractions of Micropia, the world's first "zoo for microbes", which opened in early fall 2014.

The current outbreak of Ebola in West Africa and the accompanying media frenzy are likely to have raised interest in the Amsterdam exhibit. But one of the ideas behind Micropia is precisely to counter the public perception of what microbes are about. They are not just a the literally microscopic fringe of biodiversity but comprise the largest part of it.

Microbes live on and inside everyone of us - often to mutual benefit. In the human gut many of of them help break down the nutrients from the food we eat. Thousands of different types of microbes are happily living in our intestine, mouth or even between our toes. But Ebola is not one of them.

Deadly biodiversity

The virus is dangerous to humans because - given the rather sudden exposure - the latter can't genetically adapt to it fast enough, explains Jasper Buikx, a senior microbiologist at Micropia. Consisting of barely more than strings of DNA inside a protein shell, viruses have throughout evolution developed along with the host organisms on whom they depend to survive and replicate.

"If a virus has been present in a population of animals for thousands of years, the animals will have adapted to it,” he said. “But that only works if the population is genetically diverse enough. There's trouble if a group of animals or plants is genetically too similar. A mutated form of the virus may then just wipe them all out because there are no genetic variants in the population resistant to it."

In this sense viruses are not enemies of biodiversity but enable it to thrive through a kind of destructive selection. This long standing "co-evolution" of host and pathogens, as biologists put it, is the reason why humans do not usually die from the viruses causing common coughs and colds. And the reason why many types of bats don't die from Ebola. But why did the latter become a problem for humans?

Globalization a game changer

The Ebola virus has been around for ages in certain parts of Africa that used to be remote from human settlements. Any human who did catch the virus in sparsely inhabited areas from an infected animal, would not have passed it on. But globalization has changed that, says Marcel Tanner, who is director of the Swiss Tropical and Public Health Institute.

"Probably at the end of 2013 a single person picked up the virus from an animal,” he said. “But rapid urbanization and increasing human travel in the region meant this person could pass on the virus to many others even in the short time he or she may have had left to live. Add to this the rather weak local health systems and you can see why the disease spread quickly."

Bat populations in forest areas are considered an important reservoir for the virus. Apart from Ebola they harbour hundreds of viruses harmless to bats but potentially deadly to humans, he adds.

"Bats are genetically very old species,” said Tanner. “Throughout evolution they have had lots of time to adapt to a large number of viruses in the region. It is possible that somewhere down the evolutionary path in the future humans will adapt to Ebola as well."

Logging, habitat destruction increase exposure to viruses

For now, it seems, humans are going to take the hit. And for a large part they are responsible for it. If manmade globalization may still be too diffuse a cause to consider, others are not. One of these is the ax that humans are putting to their planet's biodiversity.

"Deforestation and habitat destruction have brought humans and animals into much closer contact than ever before, increasing the risk of transmitting pathogens that humans can't deal with," said Jane Smart, head of the Global Species Programme at the International Union for the Conservation of Nature (IUCN). And the trend is continuing given the rising commercial demand for "forest products" including bush meat, timber or medicinal plants.

One way to prevent deadly viral outbreaks like Ebola from occurring is therefore to protect forests, she adds. This implies reining in commercial interests and supplying alternative sources of income to locals.

The containment of pathogens and other benefits - sustainable access to forestry resources or new revenue models - that intact forests hold for human populations is slowly being recognized as vital. In September, in an unprecedented move, the Norwegian government made forest protection the cornerstone of a massive aid deal worth 150 million euros to Liberia, incidentally one of the countries worst hit by the Ebola crisis.

In the long term, the human impact on the globe's biodiversity may even hasten the disappearance of species through disease, says Micropia's Jasper Buikx.

"The reduction and fragmentation of animal habitats may bring down the genetic diversity of individual populations, making them more susceptible to diseases caused by viruses, bacteria and the like,” he said.

Ebola has already decimated ape populations in Africa in the past. For isolated populations of species already on the brink of extinction, a virus like Ebola may be all that is needed to push them off the cliff.

A bat in flight
Bats are a major reservoir for hundreds of viruses that are potentially dangerous to humansImage: imago
Glass model of a virus in a glass cabinet
A large glass model of the Ebola virus is one of the attractions at MicropiaImage: Micropia/Natura Artis Magistra