-John Vidal
Contd from previous issue
Yet human health research seldom considers the surrounding natural ecosystems, says Richard Ostfeld, distinguished senior scientist at the Cary Institute of Ecosystem Studies in Millbrook, New York. He and others are developing the emerging discipline of planetary health, which looks at the links between human and ecosystem health.
“There’s misapprehension among scientists and the public that natural ecosystems are the source of threats to ourselves. It’s a mistake. Nature poses threats, it is true, but it’s human activities that do the real damage. The health risks in a natural environment can be made much worse when we interfere with it,” he says.
Ostfeld points to rats and bats, which are strongly linked with the direct and indirect spread of zoonotic diseases. “Rodents and some bats thrive when we disrupt natural habitats. They are the most likely to promote transmissions [of pathogens]. The more we disturb the forests and habitats the more danger we are in,” he says. Felicia Keesing, professor of biology at Bard College, New York, studies how environmental changes influence the probability that humans will be exposed to infectious diseases. “When we erode biodiversity, we see a proliferation of the species most likely to transmit new diseases to us, but there’s also good evidence that those same species are the best hosts for existing diseases,” she wrote in an email to Ensia, the nonprofit media outlet that reports on our changing planet.
The market connection: Disease ecologists argue that viruses and other pathogens are also likely to move from animals to humans in the many informal markets that have sprung up to provide fresh meat to fast-growing urban populations around the world. Here, animals are slaughtered, cut up and sold on the spot. The “wet market” (one that sells fresh produce and meat) in Wuhan, thought by the Chinese government to be the starting point of the current Covid-19 pandemic, was known to sell numerous wild animals, including live wolf pups, salamanders, crocodiles, scorpions, rats, squirrels, foxes, civets and turtles.
Equally, urban markets in west and central Africa sell monkeys, bats, rats, and dozens of species of bird, mammal, insect and rodent slaughtered and sold close to open refuse dumps and with no drainage.
“Wet markets make a perfect storm for cross-species transmission of pathogens,” says Gillespie. “Whenever you have novel interactions with a range of species in one place, whether that is in a natural environment like a forest or a wet market, you can have a spillover event.” The Wuhan market, along with others that sell live animals, has been shut by the Chinese authorities, and last month Beijing outlawed the trading and eating of wild animals except for fish and seafood. But bans on live animals being sold in urban areas or informal markets are not the answer, say some scientists.
“The wet market in Lagos is notorious. It’s like a nuclear bomb waiting to happen. But it’s not fair to demonise places which do not have fridges. These traditional markets provide much of the food for Africa and Asia,” says Jones.
“These markets are essential sources of food for hundreds of millions of poor people, and getting rid of them is impossible,” says Delia Grace, a senior epidemiologist and veterinarian with the International Livestock Research Institute, which is based in Nairobi, Kenya. She argues that bans force traders underground, where they may pay less attention to hygiene. Fevre and colleague Cecilia Tacoli, principal researcher in the human settlements research group at the International Institute of Environment and Development (IIED), argue in a blog post that rather than pointing the finger at wet markets, we should look at the burgeoning trade in wild animals. “It is wild animals rather than farmed animals that are the natural hosts of many viruses,” they write. “Wet markets are considered part of the informal food trade that is often blamed for contributing to spreading disease. But … evidence shows the link between informal markets and disease is not always so clear cut.”
Changing behaviour: So what, if anything, can we do about all of this? Jones says that change must come from both rich and poor societies. Demand for wood, minerals and resources from the global north leads to the degraded landscapes and ecological disruption that drives disease, she says. “We must think about global biosecurity, find the weak points and bolster the provision of health care in developing countries. Otherwise we can expect more of the same,” she adds.
“The risks are greater now. They were always present and have been there for generations. It is our interactions with that risk which must be changed,” says Brian Bird, a research virologist at the University of California, Davis School of Veterinary Medicine One Health Institute, where he leads Ebola-related surveillance activities in Sierra Leone and elsewhere.
“We are in an era now of chronic emergency,” Bird says. “Diseases are more likely to travel further and faster than before, which means we must be faster in our responses. It needs investments, change in human behaviour, and it means we must listen to people at community levels.”
Getting the message about pathogens and disease to hunters, loggers, market traders and consumers is key, Bird says. “These spillovers start with one or two people. The solutions start with education and awareness. We must make people aware things are different now. I have learned from working in Sierra Leone with Ebola-affected people that local communities have the hunger and desire to have information,” he says. “They want to know what to do. They want to learn.” Fevre and Tacoli advocate rethinking urban infrastructure, particularly within low-income and informal settlements. “Short-term efforts are focused on containing the spread of infection,” they write. “The longer term – given that new infectious diseases will likely continue to spread rapidly into and within cities – calls for an overhaul of current approaches to urban planning and development.” The bottom line, Bird says, is to be prepared. “We can’t predict where the next pandemic will come from, so we need mitigation plans to take into account the worst possible scenarios,” he says. “The only certain thing is that the next one will certainly come.” Courtesy : The Guardian