OPINION: DO WE NEED TO INDUCE STRESS in the ONE-HEALTH PARADIGM?
A recent article published in the International Journal of Parasitology aims some criticism towards the relatively new ‘One-Health’ concept.
‘One Health’ focuses on disease interactions between wildlife, domestic, environmental, and human health towards contemporary health initiatives. We can think of it as a One Health Triad: human, domestic animal, and wildlife health. It’s a pretty new way to think about health and has lots of cool collaborative benefits. But yes, it’s still growing.
Dr. Andrew Thompson of Murdoch University, Australia, suggests that One Health needs to be revised to account for asynchrony in transmission dynamics between wildlife and humans. Specifically, he criticizes the platform for considering each wildlife, livestock, environmental, and human component with equal weight. Realistically, he argues, human modifications of the landscape are having direct effects on wildlife health and indirect effects on animal stress, magnifying the burden on animal immune systems possibly resulting in greater mortality. That means there are many circumstances where transmission is one-way, from animal to human. Yet, we are not focusing on the impacts of humans on animal health. Transmission dynamics are very complex, so we need to think about them using more complexity.
Personally, I think these prescribed asynchronous disease dynamics already exist within the established One Health platform. A focus on wildlife may not be explicit in ‘One-Health’ but it’s an inherent part of the way ‘One-Health-ers’ think. One must consider the dynamic abiotic and biotic effects of disease transmission within and between wild animals, domestic animals, and humans. In some cases these dynamics are generalizable among different host-pathogen systems, but many are very specific in nature.
Speaking from experience, much of my research focuses on wildlife disease reservoirs. Reservoirs are usually considered populations of animals that maintain a parasitic infection with little to no net mortality effects on the population. A reservoir population is considered a source of infection for another susceptible population, be it wildlife, domestic livestock, or in some cases, human.
Good reservoirs are usually pretty stable, robust kinds of animals. They can even be considered robust against stress. Mice, for example, are great reservoirs for a suite of pathogens: Lyme disease (Borrelia burgdorferi); Hantavirus (Sin Nombre Virus); and many ectoparasites that can carry virulent parasites.
But, like many opportunists, mice typically thrive in degraded environments like farms, cities, or resource extraction sites. That means lots of animals, potentially carrying lots of parasites, in high-human density areas. That should be pretty stressful for the animals, but stress-induced parasitism isn’t that common for these generalist species. Raccoons, coyotes, skunks are all examples of generalists that may act as disease reservoirs but are generally uninfluenced by stressors in human-dominated environments. Reservoir research is a major part of One Health programme. So, Thompson’s argument to re-focus towards a wildlife-health perspective may already inherently exist.
Do we need to re-design ‘One Health’ to incorporate weighted-impacts on disease dynamics? Perhaps, but I expect this may come with improved communication and consolidation of disease knowledge among scientists. Burgeoning domains such as zoonotic ecology, landscape epidemiology, and agricultural ecology necessarily consider complexity in their analyses are examples of this momentum. Therefore, like so many contemporary perspectives in science, it is the scientific community that must unite to combine results, discuss opinions, and maintain an evolution of the holistic perspective of One Health.
In my opinion, One-Healthers are thinking in the right direction… they just need exchange ideas a little more.
-A.Watts
SOURCES:
Thompson, A. R. C. (2013) Parasite zoonoses and wildlife: One health, spillover and human activity. International Journal for Parasitology, 43:1079-1088.
A comment on this publication can be found here:
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