The concept “a single health”, better known by his original name One Health, has invaded discourse on public health. Adopting, or highlighting an integrated approach to human, animal and environmental spheres to face the future health crises is almost imposed to run for a position or funding. All researchers know the risk: hide a poor science behind a rich concept.
The study that has just published the review Environmental Research Letters promises, on the contrary, to do the date. For the first time, a team of researchers highlights the link between the collapse of an animal population and a human health crisis. And not just any: on the one hand the massacre caused by the Batrachochytrium dendrobatidis (BD) mushroom, which makes amphibians the most threatened animal group, according to the International Union of Nature Conservation. On the other, malaria, a scourge responsible for 627,000 dead, in 2020.
The researchers headed for Costa Rica and Panama. Before the arrival of comics in Central America, in the mid -1980s, these two countries constituted amphibian biodiversity jewels. The fungus made a carnage there: 500 species have declined, 90 others have simply disappeared.
Karen Lips, of the University of Maryland, had followed the crisis at the forefront. “During a discussion, we wondered what such a devastation could have provoked on human health, says Michael Springborn, environmental economist at the University of California Davis. As the amphibians are deemed to eat mosquitoes And the mosquitoes transmit malaria, we decided to go see what was the crises of malaria in these two countries. “
” A natural experiment “
The two researchers and their colleagues knew how to have detailed data on the progression of the fungus: year after year, the local authorities have listed its progress, on the scale of the 136 cantons, from the northwest to the south-east of the Costa Rica, between 1986 and 1993, then from west to east of Panama, from 1993 to 2010.
They gathered information, on the same scale, on malaria. The result is spectacular: three years after the first important declines of frogs, toads or salamanders, the cases explode and remain on a high plateau (more than one in a thousand) for six years, before lowering.
The mechanism appears quite obvious: the amphibians devour insects, especially their larvae, the tadpoles gave themselves eggs and larvae of mosquitoes floating in the ponds. In what proportion? In the absence of data on mosquito densities in Central America, the researchers are progressing rare work carried out elsewhere: a study carried out in Indiana in 2003, thus showed a 98 % drop in larval mosquitoes in the presence of salamanders. And the conclusion of imposing itself: fewer amphibians, more insects and therefore more malaria.
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