Wildlife markets are hotbeds of disease

In 2003, the world met SARS. The coronavirus wreaks havoc on a patient’s immune system, and even after treatment patients have gone on to suffer from long-term diseases like osteoporosis or lung disease. It’s thought that the virus jumped from animals to humans, facilitated by markets in southern China known for trading in wildlife and wildlife parts. The infection eventually spread to 29 countries on five continents. In all there were 8,098 human cases and 774 deaths. The outbreak cost China some $16.8 billion in lost tourism revenue.

The illegal trade in wildlife is not only devastating ecologically; it also has a real and measurable impact on human health and economics. And the problem is not just in China.

Laos, more properly known as the Lao People’s Democratic Republic or Lao PDR, is home to a stunning diversity of mammal, reptile, bird, and amphibian species. Many of them are endemic—animals found there and no place else—like the Phou Khao Khouay leaf-nosed bat, the Truong Son muntjac, and the critically endangered Saola. Like in China, there’s a tremendous amount of illegal trade in wildlife and wildlife parts in Laos. The extent of that trade, and its possible consequences for human health, were recently revealed in a study led by Zoe F. Greatorex and Sarah H. Olson of the Wildlife Conservation Society.

First, 375 basic surveys of 93 markets scattered across 15 of the 17 Laotian provinces were carried out over the course of three years. These surveys were simply to identify markets in which wildlife was sold, and they were carried out discretely by two Laotians who could blend in to the crowd.

Then, the researchers conducted detailed surveys in the winter and spring of 2012 at 44 markets. These surveys documented which species were being sold and how many individual animals per species were offered to buyers. In addition, researchers recorded the prices at which wildlife was sold, the origins of market visitors (information gleaned from license plates visible in the parking areas), and the hygiene of merchants and butchers. (For example: Did the butcher clean his or her equipment after every animal? Did the vendors wash their hands often enough?)

Finally, to assess the potential for the spread of zoonotic pathogens from wild animals to humans, the researchers focused on seven markets with a particularly high level of wildlife trade, using the data collected during the first two phases of the study. Each of these markets was observed selling more than 100 animals per day on at least four different days.

Nearly 7,000 animals were for sale for sale at these markets, weighing more than 2,000 kilograms combined. Across all 93 markets, they recorded 33,752 animals for sale, with nearly 7,000 of them belonging to species of conservation concern, including turtles, tortoises, deer, and lorises. This volume in wildlife trade is on par with some of the most prolific wildlife markets elsewhere, like in Equatorial Guinea, Myanmar, and China.

The mammals alone represented 12 taxonomic families ranging from rodents to primates, species previously documented to be capable of transmitting at least 36 pathogens, like Ebola, Lassa fever, Marburg virus, monkeypox, dengue, yellow fever, West Nile, and others. (Because their ability to transmit pathogens isn’t clear, carcasses that were smoked, dried, fermented, or frozen were omitted. The researchers concentrated instead on living animals or ones freshly slaughtered for this analysis.)

Though proper hygiene can limit the transmission of many of these pathogens, the researchers documented remarkable disregard for biosecurity. “In half-hour observations of 11 wildlife vendors in these seven markets, hand washing was only observed to be performed by one individual,” write the researchers. Only four of the markets even had running water available. And while five of the six markets that also sold domestic meat products had zoning regulations to keep livestock products and wildlife products separate, that didn’t seem to apply to poultry, fish, or produce—only to mammals. The possibility—likelihood, even—for cross-contamination in that sort of environment is mind-boggling.

To find out just who was purchasing all these wildlife products, the researchers compared the price of wild animals to that of fresh domestic pork. In most cases, wildlife generated a lot more revenue. In early 2012, one kilogram of pork could be sold for around 34,000 Kip, which is about $4. A kilogram of brush-tailed porcupine sold for four times as much. This suggests that urban consumers eat wildlife as a luxury, rather than for nutrition or subsistence. And since the average Laotian makes around $4 per day, there’s a high economic incentive to sell wildlife meat rather than livestock. A kilogram of pork represents around one day of income, while a kilogram of bat equates to three days’ worth of income.

The impacts of the Laotian wildlife trade are far-reaching. Not only does the study demonstrate the enormous potential for zoonotic spillover and the serious damage that the wildlife trade does to Laotian ecosystems, but it also reveals a challenge to food security to the poorest Laotians, who have historically relied on subsistence hunting for protein.

If wildlife is to be harvested, conclude the researchers, it needs to be done with serious oversight and enforcement, as per the Lao PDR Wildlife and Aquatic Law. Because it poses risks both to public health and to biodiversity, they say this form of wildlife trade provides a unique opportunity for public health officials, conservationists, law enforcement, and other groups to collaborate on addressing the underlying economic realities that drive the sale of wild animals. – Jason G. Goldman | 06 April 2016

Source: Greatorex ZF, Olson SH, Singhalath S, Silithammavong S, Khammavong K, Fine AE, et al. (2016) Wildlife Trade and Human Health in Lao PDR: An Assessment of the Zoonotic Disease Risk in Markets. PLoS ONE 11(3): e0150666. DOI: 10.1371/ journal.pone.0150666.

Header image: A wildlife market stand in Lao PDR via Zoe Greatorex/WCS, used with permission.