Human-modified ecosystems have more hosts for diseases transmitted from animals to humans, compared to undisturbed habitats, according to a study published in Nature. Researchers highlight the need to monitor agricultural, livestock and urban ecosystems.
The global transformation of the natural environment for agricultural, livestock or urban use has upset the balance of wild animal communities. A study led by several British institutions has shown that species that carry zoonotic diseases, known to infect humans, benefit from these changes in land use.
“It is difficult to know if the risk of these types of ailments is higher now than in the past. However, at this time, there are many factors that increase the likelihood that isolated disease outbreaks will develop into major epidemics. For example, the world is much more connected by road and air than ever, making it easy for diseases to spread more rapidly to more densely populated areas.”Says Rory Gibb, a co-author of the study and a scientist at the Center for Research in Biodiversity and Environment at University College London.
For the study, the researchers accessed PREDICTS, a database that gathers local species information from hundreds of studies on ecological communities, along gradients of landscape disturbance, from natural vegetation to agricultural and urban ecosystems.
The team used 6,801 locations around the world to analyze how populations and communities of zoonotic host species transform, on average, as landscapes change from natural vegetation, to agricultural, grassland and urban ecosystems.
“We found that, under increasing intensities of human land use, ecological communities shift to become increasingly dominated by zoonotic host species, particularly in secondary (reclaimed), managed (agricultural and plantation) habitats. and urban”Gibb emphasizes.
The work, which is published in the magazineNature, can help prevent future contagion of diseases caused by animal hosts. "There is some evidence that new zoonoses [new and previously undiscovered pathogens] are emerging at an ever increasing rate and that this may be due to increasing rates of human-driven impacts on the environment and biodiversity”. says the co-author.
But, he adds, “this trend is difficult to measure conclusively. Undoubtedly, the use of improved diagnostics and new genomic technologies will help us advance in the detection of new diseases”.
However, these responses depend on the grouping of some particular species: rodents, passerines and bats show a particularly clear and strong divergence between host and non-host species, while in carnivores and primates it is not detected, according to the study.
The researchers stress that we may need to alter the way we use land around the world, to reduce the risk of future contagious effects of infectious diseases.
Global land use change is characterized primarily by the conversion of natural landscapes for agriculture, particularly for food production. "Our findings underscore the need to manage agricultural landscapes to protect the health of local people while ensuring their food security.“Says Kate Jones, co-author and researcher at University College London (UCL).
These zoonotic diseases such as Ebola, Lassa fever and Lyme disease, which are caused by pathogens that spread from animals to people and have a high healthcare cost.
“Zoonotic malaria, for example, is transmitted between primates, mosquitoes, and people around forest margins in Southeast Asia. Nipah virus emerged, for the first time, in association with interactions between cattle and bats in agricultural landscapes. Another important and widespread disease is Lyme disease, the incidence of which is often higher in fragments of modified and recovering forests, where the ecological community is particularly effective in transporting and transmitting the bacteria, ”says Gibb.
The researchers stress that while there are many other factors that influence disease risks, the results point to strategies that could help mitigate the risk of infectious disease outbreaks comparable to COVID-19.
“As agricultural and urban lands are forecast to continue to expand in the coming decades, we should strengthen disease surveillance and disposition in those areas that are experiencing a large amount of land disturbance as it is increasingly they probably have animals that could be harboring harmful pathogens, ”adds Jones.
For his part, David Redding, another of the UCL authors, emphasizes that the work “provides a context to reflect on more sustainable changes, so that potential risks are taken into account, not only for biodiversity, but also for human health ”.
Kate E. Jones et al. "Zoonotic host diversity increases in human-dominated ecosystems"Nature(August, 2020)