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Published On: Thu, Aug 14th, 2014

Ebola virus: The ecology of disease

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If I were an indigene of Yambuku village in the Democratic Republic of the Congo, I would have asked the name of the Ebola River, lying in its domain changed, as it has brought odium and stigma to it.

Ebola virus is now synonymous with Yambuku. You can’t trace the history of the virus without mentioning Yambuku. That’s the baggage the village has to carry, since the first outbreak of the virus in its domain in 1976.

Today, Yambuku is known all over the world, not for any good reason. Even if there are gold and oil deposit in that village, I believe that no one would want to have anything to do with it.

But, be as it may, the indigenes of the village were not the people who named the river, Ebola; after all, the river run through it to Sudan. Whether the name is changed or not it makes no difference. After all, The Democratic Republic of the Congo was once Zaire.

Don’t blame Yambuku and its people; blame the virus that has become a global terrorist with its fatality rate. It’s unfortunate that it originated from there, as the Yambuku people are equally the victims; the first to suffer the outbreak of Ebola hemorrhagic fever.

Today, the strain of Ebola has been recorded as one of the highest case fatality rates of any human virus; roughly 90 percent. What has been going around has now come to us live, like a thief in the middle of the night, since the masqueraded visit by a Liberian, a harbinger of evil to Nigeria, putting everybody on edge.

Trust Nigerians; they seem to be making jokes out of a very serious matter. Nobody wants to shake hand with anybody anymore, as everybody seems to be a victim. Even, market women are not left out of the huge jokes; they’re now wearing globes to sell their wares. Bitter Kola market is now booming, since Prof. Morris Iwu’s inconclusive research on the product suggests it could prevent or cure Ebola Virus.

For what was never our own making, Nigerians are now becoming persona non grata of sort in Europe and America.

This time again, like every bad thing considered by the western world to have originated from Africa, Ebola virus is said to have come from the animals on the African continent. So, eating bush meat today has been considered a high risk.

Africa is not to blame for all of these. We have all forgotten that when we do things in ecosystems that erode biodiversity, like we chop forests into bits or replace habitat with agricultural fields, we tend to get rid of species that serve a protective role.

Public health experts have begun to factor ecology into their models, as they claim that there are a few species that are reservoirs and a lot of species that are not. The ones we encourage are the ones that play reservoir roles.

The environment’s role in the emergence of diseases is apparent in the connections between the direct consequences of human changes to urban and rural landscapes and ecosystems, and the secondary effects on disease emergence factors.

Overwhelming evidence points to human demographic changes as the major direct and indirect factor contributing to the increase in infectious disease, with somewhat different dynamics and mechanisms at work in urban and rural environments.

Poverty, poor living conditions, including lack of sanitation and infrastructure for waste-water and solid waste management, increases opportunities for vector- borne diseases and others pass from animals to humans.

The geographic spread and expansion into peri-urban areas of the mosquito Aedes albopictus, exquisitely adapted for breeding in discarded plastic containers and used automobile tires, is a good example of how a potential vector of viral diseases has taken advantage of environmental change.

Lack of sanitation and waste water treatment, and industrial scale intensification of animal production systems the world over; contribute to exotic species, and the proliferation and spread of water and food-borne pathogens. Increasingly frequent outbreaks of infections are caused by these and other organisms, many of which may eat alongside or prey on wild mammals and birds as natural parasites.

In rural areas population and consumption play a less direct role in contributing to disease emergence, particularly as rural emigration is fuelling the demographic explosion in cities. It is more that urban areas are driving a sustained increase in the timber trade, agriculture, stock raising and mining, resulting in turn in deforestation and changes in land use that are transforming rural landscapes and natural areas in ways that often facilitate the emergence of disease.

The spread and intensification of farming results in the development of irrigation systems, ideal breeding sites for mosquitoes and a habitat for opportunistic insects and rodents that may be vectors or reservoirs for disease. Dams provide a favourable habitat for other vectors.

There’s a term biologists and economists use these days, ecosystem services, which refers to the many ways nature supports the human endeavor. Forests filter the water we drink, for example, and birds and bees pollinate crops, both of which have substantial economic as well as biological value.

If we fail to understand and take care of the natural world, it can cause a breakdown of these systems and come back to haunt us in ways we know little about. A critical example is a developing model of infectious disease that shows that most epidemics — AIDS, Ebola, West Nile, SARS, Lyme disease and hundreds more that have occurred over the last several decades, don’t just happen. They are a result of things people do to nature.

Disease, it turns out, is largely an environmental issue. Sixty percent of emerging infectious diseases that affect humans are zoonotic, they originate in animals. And more than two-thirds of those originate in wildlife.

Teams of veterinarians and conservation biologists are in the midst of a global effort with medical doctors and epidemiologists to understand the “ecology of disease.” It is part of a project called Predict, which is financed by the United States Agency for International Development.

Experts are trying to figure out, based on how people alter the landscape, with a new farm or road, for example, where the next diseases are likely to spill over into humans and how to spot them when they do emerge, before they can spread. They are gathering blood, saliva and other samples from high-risk wildlife species to create a library of viruses so that if one does infect humans, it can be more quickly identified. And they are studying ways of managing forests, wildlife and livestock to prevent diseases from leaving the woods and becoming the next pandemic.

It isn’t only a public health issue, but an economic one. The World Bank has estimated that a severe influenza pandemic, for example, could cost the world economy $3 trillion.

The problem is exacerbated by how livestock are kept in poor countries, which can magnify diseases borne by wild animals. A study released earlier this month by the International Livestock Research Institute found that more than two million people a year are killed by diseases that spread to humans from wild and domestic animals.

That’s why experts say it’s critical to understand underlying causes. “Any emerging disease in the last 30 or 40 years has come about as a result of encroachment into wild lands and changes in demography.

Emerging infectious diseases are either new types of pathogens or old ones that have mutated to become novel, as the flu does every year. AIDS, for example, crossed into humans from chimpanzees in the 1920s when bush-meat hunters in Africa killed and butchered them.

Diseases have always come out of the woods and wildlife and found their way into human populations, the plague and malaria are two examples. But emerging diseases have quadrupled in the last half-century, experts say, largely because of increasing human encroachment into habitat, especially in disease “hot spots” around the globe, mostly in tropical regions. And with modern air travel and a robust market in wildlife trafficking, the potential for a serious outbreak in large population centers is enormous.

The best way to prevent the next outbreak in humans, specialists say, is with what they call the One Health Initiative, a worldwide program, involving more than 600 scientists and other professionals, that advances the idea that human, animal and ecological health are inextricably linked and need to be studied and managed holistically.

It’s not about keeping pristine forest pristine and free of people; it’s learning how to do things sustainably. If you can get a handle on what it is that drives the emergence of a disease, then you can learn to modify environments sustainably.

The scope of the problem is huge and complex. Just an estimated 1 percent of wildlife viruses are known. Another major factor is the immunology of wildlife, a science in its infancy.

Most critically, Predict researchers are watching the interface where deadly viruses are known to exist and where people are breaking open the forest, as they are along the new highway from the Atlantic to the Pacific across the Andes in Brazil and Peru.

It might mean talking to people about how they butcher and eat bush meat or to those who are building a feed lot in bat habitat.

EcoHealth also scans luggage and packages at airports, looking for imported wildlife likely to be carrying deadly viruses. And they have a program called PetWatch to warn consumers about exotic pets that are pulled out of the forest in disease hot spots and shipped to market.

All in all, the knowledge gained in the last couple of years about emerging diseases should allow us to sleep a little easier, says Dr. Epstein, the EcoHealth veterinarian. “For the first time,” he said, “there is a coordinated effort in 20 countries to develop an early warning system for emerging zoonotic outbreaks.”


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