In the 1990s and 2000s, Costa Rica and Panama experienced spikes in malaria cases. The massive loss of amphibians in the region from a lethal fungal disease may contribute to the prevalence of this human disease.
The expansion of the fungal disease chytridiomycosis was a slow-moving disaster, leading to a decade-long amphibian decline globally. From the 1980s to the 2000s, the wave moved from north to south across Costa Rica and Panama, hitting different areas at different times. An analysis of local ecological surveys, public health records and satellite data suggests a link between amphibian deaths and increases in human malaria cases as the wave has passed, researchers report in October. Environmental Research Letters.
Teasing the ways biodiversity loss “ripples”[s] by embracing and affecting ecosystems[s] humans” can provide support for preventive actions against other ecological threats, says Michael Springborn, an environmental economist at the University of California, Davis.
On average, each county in Costa Rica and Panama had 0.8 to 1.1 additional cases of malaria per 1,000 people per year for about six years starting two years after the amphibian losses, Springborn and colleagues found.
Other research suggests that amphibians are a major deterrent to mosquito populations. The amphibian larvae eat the mosquito larvae, and the animals compete with each other for resources, such as places to live.
So missing frogs, toads and salamanders led to more mosquitoes and potentially more malaria transmission. But it’s unclear whether the mosquito population has increased this season, Springborn says, because those data aren’t available.
Chytridiomycosis, from a fungus Batrachochytrium dendrobatidis or * bd It has led to the greatest recorded loss of biodiversity due to disease. It has caused the decline of at least 500 species globally (SN: 3/28/19). Ninety of their species are presumed extinct. Frogs and robins have suffered the greatest declines in America and Australia. International trade in the amphibian fungus is spreading globally.
Indeed, Firstborn and his colleagues wondered if the damage caused by amphibian attacks would also extend to humans. The researchers turned to Costa Rica and Panama, where the fungus moves through the ecosystem in a balanced way along the narrow strip of land in which the two regions sit, Springborn said. This meant that researchers could work with the fungus to reach a specific location. The team also looked at the number of malaria cases in those areas before and after the amphibian die-offs.
In the first two years after the decline of the animals, cases of malaria began to rise. For the next six years or so, the rates remained elevated, then began to decline again. Researchers are not sure what happened after the drop.
Studies on the connections between biodiversity loss and human health, to “promote conservation aid in the light of direct conservation of human interest,” says Hillary Young, a community ecologist at the University of California, Santa Barbara who was not involved in the project. work
“Humans would be exterminated by wildlife at a rate similar to the mass extinction of other species,” he said. “We are increasingly aware that these losses can have a major impact on human health and well-being, and especially on the risk of infectious disease.
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