Urban food waste, wild scavengers and disease
Most infectious diseases that afflict people are zoonotic: The pathogens (the agents that cause the diseases) originated in other vertebrate hosts before “spilling over” into our species. Urbanisation can facilitate the transmission of zoonotic diseases because in cities, people and other animals (wild and domesticated) live so closely together. So, developing policies that interrupt urban transmission routes is a key public-health goal. One thing that makes achieving this goal difficult is that many transmission routes are poorly understood.
The route we are interested in involves food waste. Some sources of organic waste are permanent, such as landfills—we know these permanent sources can influence zoonotic transmission. But what about transient organic waste (TOW) sources, such as public litter bins, where the availability of food waste changes over time? Their role in zoonotic disease dynamics is unknown.
Our working hypothesis is that TOW sources become transmission hotspots by attracting scavengers (animals that feed on waste), which may host zoonotic pathogens. These animals shed pathogens (in feces and urine), which then build up in the nearby environment. As people and many other animals use these sites, the risk of disease exposure rises for all.
We are studying how TOW sources influence pathogen transmission in NYC—a key first step on the road to a solid understanding of urban zoonotic-disease dynamics. And we are especially interested in Norway rats. They are notorious scavengers at trash bins and the main hosts for the bacteria that cause leptospirosis, a serious disease that has recently been infecting increasing numbers of New Yorkers. In our 2025 pilot season, we aim to answer two questions.
- Which scavengers feed on TOW? We predict that where there is more TOW and it is more accessible (e.g., not properly contained), there are more scavenger species (diversity) and individuals (abundance). Using camera traps near trash bins, we can continuously monitor scavengers and then review the footage to identify them and their interactions.
- How does TOW affect the bacterial community in topsoil? We expect the diversity and abundance of pathogenic bacteria to track the diversity and abundance of scavenger hosts. If so, then bacterial abundance and diversity will rise (1) where TOW is more abundant and accessible and (2) closer to the TOW source. We collect soil and fecal samples at different distances from bins and then use molecular tools to identify and quantify these bacteria.
This project is central to the dissertation of Taylor Rubin—indeed, it is her brainchild. The project also involves many collaborators at the Cary Institute of Ecosystem Studies, the NYC Department of Health & Mental Hygiene and the USDA Agricultural Research Service National Animal Disease Center. Molecular work (extracting and amplifying DNA) is being done in Dr John Dennehy’s lab and at the Cary Institute. Other partners are Drs Trujillo, Fabrizio Spagnolo (Long Island University) and Nash Rochmann (CUNY School of Public Health).
Taylor will also join the CURT Network, which I belong to, and work with us to build a social-ecological model of the complex network of people, TOW sources, scavengers and disease that will reveal how interventions might affect the system.
Overall, this project will promote an understanding of public-health risks near trash bins and help inform effective policies to reduce the risks.