Tracking the spread of viruses in live animal markets by building one in a lab
Lessons from an artificial ecosystem could help find ways to control the spread of dangerous viruses
If the source of the COVID-19 viral epidemic is a live animal market, as many public health experts suspect, then experiments at Colorado State University could help explain how it emerged.
Researchers there have duplicated similar conditions to an animal market in their carefully isolated biosafety lab so as to investigate how dangerous viruses can spread.
Dr. Dick Bowen, an infectious disease researcher and veterinarian who's spent a lot of time in Southeast Asia, leads the work. Seeing live animal markets in places like Indonesia inspired him to try a new strategy for studying potential pandemic-causing viruses.
"My interest has evolved into one of trying to look at what's actually happening in the real world instead of studying transmission in a sterile caging system," said Bowen in conversation with Quirks & Quarks host Bob McDonald.
Chinese scientists traced the potential source of the COVID-19 coronavirus to Wuhan's Huanan Seafood Wholesale Market where 27 of the initial 41 patients admitted to the hospital had visited.
According to the World Health Organization, the market sold other live and dead animals, including reptiles and bats, along with seafood.
Scientists found genetic similarities between the COVID-19 virus that to date has infected nearly 80-thousand people in more than two dozen countries and varieties of coronavirus in bats. This has led them to suspect it likely originated in bats before possibly infecting other live animals, and then, ultimately, humans.
In most of these markets, there are no disinfection protocols between batches of animals.- Dr. Dick Bowen, Colorado State University
Three ways viruses can jump from one species to another
The first mixed animal artificial ecosystem Bowen set up in his lab was meant to replicate barnyards. He wanted to look at the conditions under which animals would be housed before they went to to wild animal markets where they're eventually sold. In a series of experiments, he and his group observed how avian influenza moved around.
"All that work is done in what we call a 'biosafety level 3 laboratory,' where all the output air is filtered and all the effluent from one room goes through a kill tank and then the personnel involved wear appropriate personal protective equipment," said Bowen.
In this controlled laboratory setting, Bowen and his colleagues brought ducks, chickens, rats, blackbirds and pigeons with a small children's swimming pool as their water source. They then introduced ducks they'd recently infected with avian influenza. To monitor how the virus spread, they would swab samples from the animals or test for antibodies.
"We actually evaluated two different [avian influenza] viruses and interestingly, one of them transmitted from ducks to other ducks and chickens, but not to the other birds or to the rats. But the other virus, which has actually become a bit of a problem, again in China recently, transmitted to all of the species."
We have to use these kinds of systems that we're developing to come up with countermeasures or policies that might mitigate transmission of virus.- Dr. Dick Bowen, Colorado State University
But he said the more dramatic finding from these experiments, is "the little kiddie pool full of water became just massively contaminated with the virus very, very rapidly."
Bowen said he and his colleagues later tested a 'wet market' scenario with mixed live animals where different animals are placed in stacks of cages and found, "if you had infected chickens on the top cages, the quail that were below them all routinely became infected."
They've also tested camels for the MERS coronavirus, although not in a live market scenario because their lab isn't big enough.
They found that other than a "bit of a snotty nose," the camels didn't show any hint of disease. "But we could detect virus in their exhaled breath, so presumably if there was a human that wasn't protected in that same room, that would be an excellent way for them to become infected."
Call for a global ban on wild animal markets
Epidemiologists have long suspected live animal markets, which are common throughout Asia, create a "tremendous risk" because of how close animals are to each other and to humans.
"We see this with emerging new infectious diseases that (...) almost all the scary things, be it SARS, MERS, Nipah virus, Ebola, almost all of them have a component to emergence that involves human beings interacting with animals," said Dr. David Fisman, an epidemiologist at the University of Toronto.
Conditions at live animal markets may exacerbate an already risky situation, said Bowen. At live animal markets he's visited "sanitation is almost non-existent."
"In most of these markets, there are no disinfection protocols between batches of animals. And the situation is one where there's really no barrier to transmission of pathogens among those different species."
As a result, more than two hundred organizations and individuals issued an open letter urging governments around the world to close such wildlife markets, especially when "trade in live animals is commonplace."
Given the cultural importance of wild animal markets throughout Asia, Bowen doesn't think any ban — should they occur — would be effective.
Studying COVID-19 coronavirus wild animal market
Bowen said he thinks recreating a live market for the novel coronavirus could help scientists figure out how easily this virus can move from bats to other animals, but "right now we're just stunningly ignorant about even basic species susceptibility."
He hopes that within the next few months scientists will have a much better idea of what the potential animal hosts may be, other than bats and humans, to "not only for understanding transmission, but to get animal models for example to evaluate for vaccine testing."
Bowen said by studying animals in these realistic wild animal market scenarios, they could possibly "advise policy in terms of managing those animals."
"So we have to use these kinds of systems that we're developing to come up with countermeasures or policies that might mitigate transmission of virus."
Written and produced by Sonya Buyting