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Study Reveals Connections Between Environment, Animal and Human Health
Photo by Graziella DiRenzo
Dozens of species of frogs, salamanders and other amphibians vanished from parts of Latin America in the 1980s and 2000s, drawing little notice beyond a small group of ecologists. Yet the amphibian decline had direct health consequences for people, according to a study co-authored by a University of Maryland biologist.
The study, published in the journal Environmental Research Letters, links an amphibian die-off in Costa Rica and Panama with a spike in malaria cases in the region. At the spike’s peak, up to 1 person per 1,000 annually contracted malaria who normally would not have absent the amphibian die-off, the study found.
“This study shows how connected humans are to the natural environment, an idea we call One Health, which describes how the health of the environment is related to the health of the animals and the people who live there,” said Professor Karen Lips, a co-author.
From the early 1980s to the mid-1990s, a deadly fungal pathogen, Batrachochytrium dendrobatidis, traveled across Costa Rica, devastating amphibian populations. This amphibian chytrid fungus continued its path eastward across Panama through the 2000s. Globally, the pathogen led to the extinction of at least 90 amphibian species, and to the decline of at least 500 additional species.
Shortly after the mass die-off of amphibians in Costa Rica and Panama, both countries experienced a spike in malaria cases.
Some frogs, salamanders and other amphibians eat hundreds of mosquito eggs each day, and mosquitoes are a vector for malaria. Scientists wondered, could the crash in amphibians have influenced the rise in malaria cases?
To find out, the researchers combined their knowledge of amphibian ecology, newly digitized public health record data, and data analysis methods developed by economists, along with Lips’ long-term database of amphibian abundance and the arrival and spread of a wildlife disease collected in Costa Rica and Panama starting in the early 1990s.
The results show a clear connection between the time and location of the spread of the fungal pathogen and the time and location of increases in malaria cases. The scientists found no evidence of other variables that could both drive malaria and follow the same pattern of die-offs.
“Stable ecosystems underpin all sorts of aspects of human well-being, including regulating processes important for disease prevention and health,” said lead author Michael Springborn, a professor in the University of California, Davis Department of Environmental Sciences and Policy. “If we allow massive ecosystem disruptions to happen, it can substantially impact human health in ways that are difficult to predict ahead of time and hard to control once they’re underway.”
Tree cover loss was also associated with an increase in malaria cases, but not nearly to the same extent as the loss of amphibians. Typical levels of tree canopy loss increase annual malaria cases by up to 0.12 cases per 1,000 people, compared to 1 in 1,000 for the amphibian die-off.
The researchers said they were motivated to conduct the study by concerns about the future spread of similar diseases through international wildlife trade. For instance, another pathogen, Batrachochytrieum salamandrivorans, similarly threatens to invade ecosystems through global trade markets.
Springborn said measures that could help prevent the spread of pathogens to wildlife include updating trade regulations to better target species that host such diseases as our knowledge of threats evolve. These findings can also inform new conservation initiatives, including efforts in the U.S. to increase the amount of protected lands and species and quantify and manage biodiversity resources.
“The costs of putting those protective measures in place are immediate and evident, but the long-term benefits of avoiding ecosystem disruptions like this one are harder to assess but potentially massive, as this paper shows,” Springborn said.
This article is adapted from text provided by UC Davis.
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