Zoonotic infectious diseases as ecosystem disservices: a retrospective data review
Authors: Rory Wilson, Sonia Tiedt, Kris Murray
Journal: The Lancet Planetary Health (2021)

BackgroundEcosystem disservices are ecosystem-generated functions and processes that result in negative effects on human wellbeing. To effectively manage Earth, we need to not only understand the ecological responses of species and habitats to global change, but also those of pathogens. Zoonotic infectious diseases (ZIDs) are a particularly important disservice as they can affect vulnerable populations and are major developmental barriers. Despite the increasing evidence linking the emergence of ZIDs to anthropogenic and environmental changes, we still know only little about the generality of these patterns amongst ecosystem-associated diseases. This issue is compounded by the frequent neglect of such diseases in global assessments of disease impacts. Here, we aimed to identify the most relevant ecosystem-linked zoonoses, evaluate their effects and burden on human health, and assess existing evidence of potential distributional or ecological responses to global change.MethodsWe collated a comprehensive database on priority ZIDs that have been linked to the world's ecosystems in the Global Infectious Diseases and Epidemiology Network. For each ZID, we sought to assess the current knowledge regarding overall global health effects (measured by the availability of annual case, mortality, and burden data), current capacity to medically treat or prevent the ZID (based on vaccine and treatment availability) and susceptibility or response to global change. To identify effects of global change, we systematically searched peer-reviewed publications from Web of Science using each ZID name and any synonyms and causative agents, in combination with a selection of ecological and anthropological change terms (relating to climate change, agriculture, urbanisation, forest fragmentation, and livestock keeping). Our search was restricted to empirical and review articles published between Jan 1, 1970, and May 1, 2018, in the English language. We extracted and classified responses into three distinct categories regarding changes in ZID distribution, changes in epidemiology or ecology (eg, association with a new habitat or vector), and changes in temporal occurrence (annual cases or outbreaks). For each impact, causative changes were listed and included in the analysis.FindingsNearly every ZID we identified (40 [95·2%] of 42) was associated with epidemiological or health burden changes in response to ecological change. Climate change, agricultural practices, and urbanisation were most frequently implicated. Notably, single ecological or anthropogenic factors were rarely suggested (three [7·1%] of 42 ZIDs), with multifactorial changes implicated in the remaining ZIDs. Only four (9·5%) ZIDs had effective or highly effective treatments available (in terms of those without substantial limitations or side-effects and percentage of patients recovered when undergoing the treatment; 60–90% being effective and >90% being highly effective) and 17 (40·5%) had only supportive therapy indicated.InterpretationWe found effects of ecological change to be almost ubiquitous among ecosystem-linked zoonoses. Further quantification of the global burden of ecosystem-associated ZIDs, paticularly those with sporadic outbreaks and non-fatal health outcomes, is urgently needed to prepare for potential increased burdens or future outbreaks. Overall the present results can be used to identify shortlists of currently understudied ZIDs that pose potential future global health threats, which could be controlled with appropriate ecosystem management.FundingNatural Environment Research Council.