Saudi Press

Saudi Arabia and the world
Sunday, Jun 01, 2025

How leeches could help prevent future coronavirus outbreaks: blood suckers provide evidence of wildlife that carry animal viruses

Digested blood from leeches’ stomachs contains the DNA of animals the parasites have fed on, giving an idea of wildlife diversity in an area. This could help the fight against illegal hunting, and thus reduce the risk of novel viruses passing from wild animals to humans, as coronavirus may have done

A pioneering method for monitoring wild animal populations, developed in a nature reserve in southwest China may become an important tool in the prevention of future virus outbreaks – and the solution may lie in the gut of another parasite.

Using the latest biotechnology, a team led by Professor Douglas Yu of Britain’s University of East Anglia extracted DNA from digested blood in leeches’ stomachs, determined what animals they had fed on, and then produced a model of the distribution of wild animals in the Ailao Shan Nature Reserve in Yunnan province.

The same DNA analysis method could feasibly be used to examine drain water for evidence of illegal wildlife consumed or traded in markets, Yu says.

It took the team almost five years and more than 30,000 leeches, and now they hope to see the methodology applied to combat illegal trafficking of animals captured in the wild.

Wild animals are a reservoir of viruses that, due to their ability to rapidly change genetic make-up, regularly “jump” to other species, including humans.

Severe acute respiratory syndrome (Sars) is believed to have originated in bats, before the virus jumped to civet cats and then humans.

Human immunodeficiency virus (HIV) is suspected to have made the leap from chimpanzees to humans in the early to mid-1900s. The origin of the 2019 novel coronavirus is still unclear, but pangolins, the world’s most trafficked animal, are thought to be part of the transmission chain. Bats may have passed the virus on to the scaly animals before they infected humans, scientists say.

Hunting, trapping and eating wild animals brings people into contact with these microscopic parasites.

“Wildlife is dangerous. It is dangerous to catch, handle and consume,” says Yu, an American-born Chinese who is also a principal investigator at the Kunming Institute of Zoology in Yunnan.

Yu’s field is ecology, a branch of biology that studies interactions between living organisms and their environment. He is a pioneer in using environmental DNA (eDNA) in ecological research. eDNA is the “molecular soup” of small fragments of DNA that different animals have shed into the environment.

Until recently, biotechnology couldn’t separate these individual bits of DNA in the “soup” to identify which animals they came from. But the latest technology can process multiple DNA molecules at the same time, and it has become a powerful forensic tool.

Without seeing or touching the animals, their presence can be detected from a sample of soil, water – or the remnants of digested blood in a leech’s stomach.

A major problem is knowing exactly what lives in a forest. Camera traps can be used, but they do not generally pick up small animals. Walking across the terrain, trying to spot wildlife, is labour-intensive and ineffective. “Most animals don’t want to be seen,” Yu says.

Land leeches, driven by a voracious appetite for blood, are far better at finding animals in the thick jungle than humans are.
They are not picky eaters – a frog’s blood is as good as a bear’s. They are plentiful, too. Summer visitors to the forests of Yunnan frantically empty their shoes of leeches every few minutes.

In 2015, Yu’s team set out to survey Yunnan’s forests for wildlife through the eyes – or stomachs – of leeches, with the goal of developing a reliable method of wildlife detection from their DNA in their stomachs.

Located 170km south of Kunming, Ailao Shan Nature Reserve is roughly the size of Singapore – a 6km wide and 125km long strip of old-growth forest clinging to “a chain of top halves of mountaintops”. Hemmed in on all sides by agricultural land, the reserve “has some of the best wildlife still in China, but it has not been properly surveyed since 1981”, Yu says. Illegal hunting of wild animals occurs there.

The scientists paid park rangers to collect leeches during their regular patrols and between them covered the entire territory.

Yu’s team extracted DNA from the leeches’ stomachs, then applied sophisticated statistical software that could compare the different DNA sequences against animal DNA sequences in existing databases, similar to how facial recognition software matches an image of an individual face from a set of millions.

The leeches proved to be effective in revealing the animals hiding out in Ailao Shan. The DNA of Asian black bear, sambar deer, macaque, leopard cat, serow antelope, as well as of numerous birds, frogs, and toads was detected in their stomachs. The list included both endangered and commonly hunted animals.

From the data, Yu’s team made a model of the animals’ distribution in Ailao Shan.

The results closely matched the biology of the animals. “The right species were found in the right places,” Yu says. It also gelled with previous records of animal sightings in Ailao Shan. The leeches could be trusted.

At the beginning, however, there had been scepticism. Small pilot studies in 2012 showed promise, but a large-scale project had never been attempted.

“We did everything for the first time – from designing an effective way to pay the rangers for their work collecting leeches, to molecular analysis and statistical models. We had to string together a lot of different methods,” Yu says.

The team also had to improvise. “Normally you would need a specialist, ultra-clean lab [to avoid cross-contamination with DNA from other organisms], but we did not have enough such facilities. So another approach was using new apartments that never been lived in and so are unlikely to have DNA from other sources. We rented a few for a month at a time in Kunming and set up UV lights and DNA extraction equipment.”

The results were timely. “We certainly did not anticipate a coronavirus epidemic happening,” Yu says. “The government now says that it may ban wildlife markets permanently [in China] and also crack down on the wildlife trade.”

Intensive monitoring of wildlife would be a vital part of the ban’s enforcement. First, the baseline of animal abundance must be established, followed by repeated surveys to measure the effectiveness of protection measures. Yu says that his team is “ready for that … we have provided the methodology in anticipation. The same methods could also be applied to drain water from markets to detect wildlife.”

He adds that the method is affordable. “The cost of each survey would be a few hundred thousand yuan. Relative to money spent on many other things in China, it is a small amount.”

Yu points out that the risks from the wildlife trade and consumption do not just come from China.

“There is subsistence hunting everywhere in the world. Only a small proportion of Chinese eat wildlife, but this being China, a small proportion becomes a very large number, and these consumers are financing a supply chain of hunters, transporters and sellers that are exposing themselves to infection by novel viruses, one of which appears to have set off this year’s coronavirus epidemic.

“There is a massive amount of hunting in Southeast Asia, with much of it to supply the Chinese market. I am a little surprised this [novel coronavirus outbreak] had not yet happened where there is even more hunting, like in Vietnam for example,” he adds.

“There is a traditional Chinese medicine idea that wild animals have this authenticity, a ‘wildness’ to them, that it is healthy to eat them and that it makes you stronger. As the current epidemic shows, it is completely the opposite,” he says.

“The safest thing to do is leave wild animals be and then nothing happens. Don’t buy wildlife products, because that pays lots of people to hunt and handle them, and another person will get infected and start yet another epidemic in the future. People have to understand that buying wildlife medicines, meat, bones, horns, scales and skins puts all our lives and whole economies at risk.”

Newsletter

Related Articles

Saudi Press
0:00
0:00
Close
OPEC+ Agrees to Increase Oil Output for Third Consecutive Month
Turkey Detains Istanbul Officials Amid Anti-Corruption Crackdown
Meta and Anduril Collaborate on AI-Driven Military Augmented Reality Systems
EU Central Bank Pushes to Replace US Dollar with Euro as World’s Main Currency
European and Arab Ministers Convene in Madrid to Address Gaza Conflict
U.S. Health Secretary Ends Select COVID-19 Vaccine Recommendations
Trump Warns Putin Is 'Playing with Fire' Amid Escalating Ukraine Conflict
India and Pakistan Engage Trump-Linked Lobbyists to Influence U.S. Policy
U.S. Halts New Student Visa Interviews Amid Enhanced Security Measures
Trump Administration Cancels $100 Million in Federal Contracts with Harvard
SpaceX Starship Test Flight Ends in Failure, Mars Mission Timeline Uncertain
King Charles Affirms Canadian Sovereignty Amid U.S. Statehood Pressure
Iranian Revolutionary Guard Founder Warns Against Trusting Regime in Nuclear Talks
UAE Offers Free ChatGPT Plus Subscriptions to Citizens
Lebanon Initiates Plan to Disarm Palestinian Factions
Iran and U.S. Make Limited Progress in Nuclear Talks
The Daily Debate: The Fall of the Dollar — Strategic Reset or Economic Self-Destruction?
Trump Administration's Tariff Policies and Dollar Strategy Spark Global Economic Debate
OpenAI Acquires Jony Ive’s Startup for $6.5 Billion to Build a Revolutionary “Third Core Device”
Turkey Weighs Citizens in Public as Erdoğan Launches National Slimming Campaign
Saudi-Spanish Business Forum Commences in Riyadh
Saudi Arabia and Spain Sign MoU to Boost SME Sectors
UK Suspends Trade Talks with Israel Amid Gaza Offensive
Iran and U.S. Set for Fifth Round of Nuclear Talks Amid Rising Tensions
Russia Expands Military Presence Near Finland Amid Rising Tensions
Indian Scholar Arrested in Crackdown Over Pakistan Conflict Commentary
Israel Eases Gaza Blockade Amid Internal Dispute Over Military Strategy
President Biden’s announcement of advanced prostate cancer sparked public sympathy—but behind closed doors, Democrats are in panic
A Chinese company made solar tiles that look way nicer than regular panels!
Indian jet shootdown: the all-robot legion behind China’s PL-15E missiles
The Chinese Dragon: The True Winner in the India-Pakistan Clash
Australia's Venomous Creatures Contribute to Life-Saving Antivenom Programme
The Spanish Were Right: Long Working Hours Harm Brain Function
Did Former FBI Director Call for Violence Against Trump? Instagram Post Sparks Uproar
US and UAE Partner to Develop Massive AI Data Center Complex
Apple's $95 Million Siri Settlement: Eligible Users Have Until July 2 to File Claims
US and UAE Reach Preliminary Agreement on Nvidia AI Chip Imports
President Trump and Elon Musk Welcomed by Emir of Qatar Sheikh Tamim with Cybertruck Convoy
Strong Warning Issued: Do Not Use General Chatbots for Medical, Legal, or Educational Guidance
Saudi Arabia Emerges as Global Tech Magnet with U.S. Backing and Trump’s Visit
This was President's departure from Saudi Arabia. The Crown Prince personally escorted him back to the airport.
NVIDIA and Saudi Arabia Launch Strategic Partnership to Establish AI Centers
Trump Meets Syrian President Ahmad al-Shara in Historic Encounter
Trump takes a blow torch to the neocons and interventionists while speaking to the Saudis
US and Saudi Arabia Sign Landmark Agreements Across Multiple Sectors
Why Saudi Arabia Rolled Out a Purple Carpet for Donald Trump Instead of Red
Elon Musk Joins Trump Meeting in Saudi Arabia
Trump says it would be 'stupid' not to accept gift of Qatari plane
Quantum Computing Threatens Bitcoin Security
Michael Jordan to Serve as Analyst for NBA Games
×