The UNIL Breakthrough: Linking Wildlife Trade to Zoonotic Risks
A groundbreaking study from the University of Lausanne's Department of Ecology and Evolution has quantified a critical link between global wildlife trade and the transmission of pathogens from animals to humans. Published on April 9, 2026, in the prestigious journal Science, the research reveals that wild mammals involved in trade are 1.5 times more likely to share infectious agents—such as viruses, bacteria, fungi, and parasites—with humans compared to non-traded species. This finding underscores the urgent need for enhanced biosurveillance and trade regulations, particularly as Europe plays a significant role in both legal and illegal wildlife markets.
The study, led by former UNIL postdoctoral researcher Jérôme M.W. Gippet (now at the University of Fribourg) and supervised by Associate Professor Cleo Bertelsmeier, analyzed four decades of import-export data spanning legal and illegal activities. It highlights how prolonged exposure in trade networks amplifies pathogen spillover risks, with species accumulating an additional shared pathogen with humans roughly every nine to ten years of market presence.
This research not only bridges ecology and public health but also positions UNIL as a leader in addressing Anthropocene challenges like biological invasions and emerging diseases.
Global Wildlife Trade: Scale and Scope
The wildlife trade encompasses live animals for pets, zoos, and research, as well as products like fur, skins, horns, and scales. It involves approximately one quarter of all terrestrial mammal species worldwide—over 2,079 species documented in trade records. In Europe, the EU serves as a major transit hub and consumer market, with nearly 5,200 seizures recorded in 2023 alone, primarily involving European eels, timber, and medicinal plants, though mammals like big cats and primates are also seized.
Legal trade is regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which lists over 40,900 species. However, illegal trade persists, with Europe reporting significant volumes. A 2025 TRAFFIC report notes the EU's role in trafficking critically endangered species, amplifying risks beyond extinction to public health. Zoonotic diseases, which account for 75% of emerging infectious diseases globally, often trace back to such human-animal interfaces.
Unpacking the Methodology: Data-Driven Insights
Researchers compiled 40 years of CITES trade records (1980s–2020s) with comprehensive host-pathogen databases, focusing on wild mammals (non-domesticated, excluding cats, dogs, cattle). They modeled trade status, duration, and type (live vs. products, legal vs. illegal) against pathogen sharing probabilities using statistical analyses like generalized linear mixed models.
- Trade data: Permits for imports/exports, seizures for illegal activity.
- Pathogen data: Known associations from literature, excluding domestic animals.
- Controls: Phylogenetic relationships, geographic range, body mass to isolate trade effects.
This rigorous approach confirmed trade as an independent driver of zoonotic potential, independent of other traits.
Key Findings: Quantifying the Threat
The study's results are stark: 41% of traded mammals share at least one pathogen with humans, versus lower rates for non-traded ones. Live-traded species, especially in markets or as pets, pose higher risks due to prolonged human contact. Illegal trade exacerbates this, as does longer market tenure—one extra pathogen per decade.
| Metric | Value |
|---|---|
| Traded vs. Non-Traded Odds Ratio | 1.5x higher pathogen sharing |
| Pathogens per Decade in Trade | +1 shared with humans |
| Traded Mammal Species Analyzed | 2,079 |
| Proportion Sharing Pathogens | 41% |
High-risk taxa include primates (e.g., rhesus macaques), carnivores (otters, bears), and rodents (sugar gliders).
Case Studies: From Outbreaks to Everyday Trade
Historical examples abound: COVID-19 linked to Wuhan's wildlife market, 2003 U.S. monkeypox from imported Gambian rats and prairie dogs, HIV from bushmeat. In Europe, seizures of live cheetahs and leopard cats highlight ongoing risks. Recent avian flu outbreaks in wild birds (581 cases in 2025) underscore broader wildlife disease dynamics, though mammalian trade focuses this study.
Exotic pets like fennec foxes and African pygmy hedgehogs, popular via social media, exemplify how consumer demand drives risky trade.
Europe's Position: Markets, Transit, and Policy Gaps
The EU enforces CITES via Regulation (EC) No 338/97, but gaps persist. A 2024 CITES-WOAH MoU addresses zoonoses, yet focuses remain on conservation over health.Learn more about this collaboration. With 2025 seizures up, including South American felids, Europe must integrate pathogen screening into trade permits. UNIL's work urges updating policies for cumulative risks.
UNIL's Department of Ecology and Evolution: A Hub of Excellence
Located on Lake Geneva's shores, UNIL's DEE spans invasive species, evolutionary genomics, host-parasite dynamics, and conservation. With diverse groups (25+ nationalities), it excels in fundamental-to-applied research, teaching MSc in Behaviour, Evolution & Conservation, and PhD programs. This study exemplifies DEE's impact on global challenges.
Spotlight on the Researchers Driving Change
Jérôme Gippet, PhD, specializes in human-wildlife interactions, invasions, and urban ecology. His UNIL postdoc under Bertelsmeier honed skills in big data and modeling. Cleo Bertelsmeier, macroecologist, uses ants to study invasions and climate impacts; cited 8,000+ times. Their collaboration yields policy-relevant science.
Photo by Jonathan Lim on Unsplash
Policy Recommendations and Global Solutions
Gippet emphasizes reducing trade volume: "Limit encounters to curb emergence." Bertelsmeier calls for fundamental research informing health. Solutions include CITES pathogen criteria, market biosurveillance, consumer awareness. Europe could lead with EU-wide screening.WOAH guidelines offer a framework.
Future Outlook: Research Careers at the Forefront
UNIL DEE offers PhDs, postdocs in ecology/evolution, fostering skills in modeling, genomics. Europe's research landscape demands experts in zoonoses, with positions in conservation biology rising. Aspiring researchers can contribute to preventing pandemics while advancing academia.
As climate change intensifies invasions, studies like this propel interdisciplinary careers, blending ecology, epidemiology, and policy.