How does the human footprint relate to changes in animal-borne diseases?

Predicting how the increased intensity of human-environment interactions will affect pathogen transmission is crucial for predicting changing disease risks and identifying appropriate mitigation strategies.

A new study shows how environmental changes are leading to the emergence of animal-borne diseases, allowing for a better understanding of transmission mechanisms and more practice in predicting delivery risks.

For the first time, researchers from Griffith University, Stanford University and the University of California used integrated stress mapping and machine learning to better understand how six vector-borne diseases (those transmitted by insect bites) respond. on human influences in different settings. stressors.

The study was published in the journal Nature Sustainability, and the results found that diseases associated with low human stress, including malaria, cutaneous leishmaniasis and visceral leishmaniasis (also known as black fever), were replaced by diseases associated with high human stress. dengue fever, chikungunya and Zika.

Human impact on the world

“Humans are really good at changing the Earth. Up to 95% of the Earth’s surface has been modified in some way by humans. , animals and insects. What we didn’t know until recently was how these changes in species alter disease risk for humans.”

Skinner explained that the results of the study improve the ability to predict these changes and will support a dynamic public health infrastructure that can adapt to changes in disease incidence across time and space.

Vector-borne diseases are a global problem

Vector-borne diseases (VBD) are highly sensitive to environmental changes, but such responses are known to be difficult to isolate because pathogen transmission depends on a combination of ecological and social responses to vectors and host, which may differ between species.

Since more than half of the world’s population is at risk of vector-borne disease, Dr. Skinner and his team have identified how changes in environments that affect the unique cycle of disease transmission show a variety of complexities.

“Vectors and pathogens often occupy their own unique niches, and each cycle of transmission responds greatly to environmental change. With an increase in human pressure, changes in the incidence of various diseases can be expected. For example, dengue fever is a highly urban pathogen.” “Malaria appears at the border of deforestation. But how urban does an area have to be for dengue to be a threat? How much forest needs to be changed before we start seeing an increase in malaria?”

These are some of the research questions the team seeks to answer, and shed light on the limits of land-use change that can lead to sudden changes in infectious disease burdens and public health needs.

For the first time, the team was able to set different thresholds for the human influence triggered by certain diseases.

Comparing six vector-borne diseases in Brazil, the team found that the incidence of the disease changed abruptly from malaria in a critical window, where the human signature ranged from moderate (4-7) to high (7-12) to severe (> 12). visceral leishmaniasis for cutaneous leishmaniasis and leishmaniasis, dengue fever, chikungunya and zika (arthropod-borne viruses transmitted by urban Aedes aegypti mosquitoes).

“These are diseases that require different vector control, diagnostic and environmental management responses. Since medical and chemical approaches alone have failed to eradicate these diseases in a sustainable manner, it is critical to manage the social and environmental conditions that favor pathogen transmission,” said Skinner. The frontier for the health of the planet And together with climatic pressures, human pressure represents a great risk of the emergence and transmission of disease and therefore poses a great threat to human well-being and the environment.

He added: “Brazil is an ideal case study location to assess the human pressure on disease transmission because it is a large and diverse country environmentally, socially and economically with many dynamic geographies, intense and land use pressures change, high incidence in many cases. diseases with diverse environments and a long-standing disease surveillance system.” throughout the country”.

source: phys.org