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Wednesday, July 17, 2024

Decimation of amphibian populations in Latin America linked to surge in human malaria cases

A UC Davis retrospective study highlights the importance of preventing ecosystem disruptions to safeguard animal and human health


By BRANDON NGUYEN — science@theaggie.org 


From the 1980s to early 2000s, populations of amphibians, including frogs and salamanders, vanished from Costa Rica and Panama. The public did not notice their mysterious disappearance except for small groups of ecologists who later discovered the underlying cause for the amphibian decline to be a deadly fungal pathogen called Batrachochytrium dendrobatidis or “Bd.”

In a retrospective study published in the journal Environmental Research Letters, a group of UC Davis researchers found an alarming link between the amphibian decline and negative consequences for human health. During the spread of the fungus, there was also a spike in human malaria cases, highlighting the need for preserving ecosystem stability.

“For amphibians, the spread of Batrachochytrium dendrobatidis (Bd)—an extremely virulent fungal pathogen responsible for massive worldwide die-offs from the resulting chytridiomycosis—has arguably caused ‘the greatest recorded loss of biodiversity attributable to a disease,’” the paper reads. 

Dr. Michael Springborn, the lead author of the study and a professor in the Department of Environmental Science and Policy at UC Davis, described why the effects of the fungal pathogen on amphibians were so deadly.

“Bd wreaked havoc through disruption of amphibian skin function, such as affecting the amphibian’s ability to regulate water on the outside and inside of their skin,” Springborn said. “It laid waste to these amphibian populations in vast numbers across a large area, including Costa Rica and Panama.”

Joakim Weill, a co-author of the study and UC Davis Ph.D. candidate at the time, explained how the team discovered the link between the amphibian decimation and human health.

“We’ve known for a while that complex interactions exist between ecosystems and human health, but measuring these interactions is still incredibly hard,” Weill said. “We got there by merging tools and data that don’t usually go together as well as through collaboration with other experts including herpetologists, who specialize in the study of reptiles and amphibians.”

Furthermore, Springborn and his team highlighted how tragedies like the amphibian die-off often go unheard of but should receive more attention. 

“The loss of these amphibians is a tragedy in its own right, and unfortunately, it’s a tragedy that only gets so much attention when there’s no connection made explicitly to human welfare or to impact on human communities,” Springborn said. “So we were motivated in this paper by an interest in trying to identify whether there were discernible impacts on human communities, and if so, how do we build an understanding of this loss? Not just the direct loss of these species, but also the indirect loss we might feel by how this disturbs the ecosystem.”

Springborn and his team found that mosquitoes had the potential to carry vector-borne diseases. According to Springborn, because there were fewer amphibians that could feed on mosquito eggs, there was an unchecked rise in the population of mosquitoes, causing the spike in human malaria cases. 

According to the study, up to one in 1,000 people contracted malaria annually during this time who would not have if the amphibian decline did not occur. 

To attempt to remediate this, Springborn advocated for a preventative approach, underscoring the need to maintain ecosystem stability for the sake of both animal and human health.

“It’s important to understand that our human systems have evolved to take advantage of the particular ecosystems and environmental systems that we live in,” Springborn said. “We probably take for granted how that environmental stability is sort of built into almost everything in things that we have — the way that we live in our homes and the way that we travel from one place to another. As we gain an understanding of these perturbations like climate change and the movement of pathogens around the world that disrupt the underlying stability, it’s worth investing and taking costly measures […] to protect against these threats ahead of time.” 


Written by: Brandon Nguyen — science@theaggie.org