The eco-epidemiology of zoonoses is far more than just host-pathogen interactions. To dig deeper into these events, researchers have dissected the complex interactions involved in zoonoses. They introduce the concept of a “zoonotic web”—a detailed network representation of the relationships between zoonotic agents, their hosts, vectors, food sources, and the environment.
This work is published in Nature Communications in the paper, “A One Health framework for exploring zoonotic interactions demonstrated through a case study.”
“Zoonotic diseases are often discussed in terms of host-pathogen interactions. Understanding the complex animal-human-environment interface remains a significant challenge,” explains Amélie Desvars-Larrive, associate professor of infectious disease epidemiology at the University of Veterinary Medicine in Vienna, Austria and resident scientist at the Complexity Science Hub, also in Vienna.
The transmission of zoonoses to humans can occur through direct contact with saliva, blood, urine, or even feces of infected animals. Indirect transmission can also occur through bites from arthropod vectors or through contact with contaminated objects, environments, or surfaces.
“Simply studying the presence of a parasite in cat feces, like Toxoplasma, doesn’t tell the whole story. Are we looking at the cat-environment, environment-human, or cat-human interface? The concept of ‘interface’ remained unclear. This motivated us to develop a novel approach to zoonoses and demonstrate it through a case study,” adds Desvars-Larrive.
The researchers first carried out a systematic literature search on all documented interactions between zoonotic sources and pathogens in Austria between 1975 and 2022. The team identified six distinct communities of zoonotic agent sharing in Austria, influenced by highly connected infectious agents, proximity to humans, and human activities. The community including humans, the oldest domesticated species (also including dogs, cats, sheep, cattle, and pigs) shares the most zoonotic agents, according to the study.
The findings also highlight the important role some animals, such as the wild boar, dog, domestic cat, yellow-necked field mouse, or the raccoon dog, and arthropods (especially ticks) play in “bridging” host communities. “Knowing which actors in the network are more influential than others can be very helpful in zoonotic disease surveillance programs, for example, as they could serve as sentinels for monitoring zoonotic agent circulation,” says Desvars-Larrive.
A major challenge for the One Health community is quantifying the interactions and risks at the human-animal-environment interface. The One Health approach recognizes the health of humans, domestic and wild animals, plants, and the wider environment are closely linked and interdependent.
Using a quantitative approach, the research confirms that zoonotic spillover in Austria is most likely to occur at human-cattle and human-food interfaces. “Eating contaminated food poses a major risk of human zoonotic infection, with Listeria, Salmonella, and Escherichia being the most frequently reported agents in our study,” says Desvars-Larrive.”
The group also hopes that the interactive map educates and arouses curiosity.
