To further examine the links (if any) between the rise in environmental practices such as animal husbandry and he use of pesticides with the occurance of pandemics, for information for a podcast.
The author of "Spillover: Animal Infections and the Next Human Pandemic," David Quammen, wrote about the probability of a coronavirus starting in animals and spreading all over the globe. He stated that such things as the growth of urban sectors, the use of pesticides and international trade have all altered ecosystems and destroyed biodiversity, while often "letting loose" viruses in the process.
Up to 1 million species of plants and animals at risk of extinction and 40% of insects are under threat according to the World Wildlife Fund, and a study by the Proceedings of the National Academy of Sciences, found that 50% of animals that once were upon the Earth with us, are already gone. Many leading scientists such as Quammen, link biodiversity loss directly to the spread of infectious diseases.
According to this study on "Infectious Disease Emergence: Past, Present, and Future" there are different ways in which humans have affected the ecosystem, with activities like agriculture, food-handling practices, and, changes in water ecosystems (an important consideration for the vector biologists). The paper states that "There are a number of ecological changes, many of them anthropogenic, which provide new opportunities for pathogens to emerge and gain access to human populations. Think of these as a sort of microbial explorers, discovering new niches—us—and exploring new territory."
According to science daily, pesticides can cause imbalances in the environment that can cause the eventual proliferation of infectious disease vectors.
In this study it was found that pesticides in the waterways may be direct cause of an increase of schistosomiasis pathogens. "Contaminated waterbodies are the problem," says Professor Matthias Liess, Head of the Department of System Ecotoxicology at the UFZ. "Before schistosomiasis can be contained, something has to be done to prevent the proliferation of the pathogens in bodies of water."
It was found that even at extremely small concentrations of pesticides that are deemed harmless in the pertinent risk assessment, that "sensitive insect species disappear whereas the populations of more resistant species such as freshwater snails proliferate." In this particular case, "insect larvae living in the water that graze the algae cover of rocks, just like the snails, are severely decimated by pesticide contamination or disappear completely," resulting in "optimum food conditions for the snails, which allows them to proliferate," in turn, creating an ideal situation for the trematode worm Schistosoma that kills around 200,000 people each year to spread
This comprehensive study from a collaborative group of researchers found in their synthesis of the literature that "since 1940 agricultural drivers were associated with >25% of all, and >50% of zoonotic infectious diseases that emerged in humans, proportions that will likely increase as agriculture expands and intensifies."
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