Cascading consequences expected

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Mange has decimated the population of vicuñas and wild guanacos in an Argentine national park created to conserve them, according to a study by the Argentine National Parks Administration and the University of California, Davis.

The results, published today in the journal PLOS ONE, suggest that domestic llamas introduced to the site may have been the source of the outbreak. Cascading consequences for local predators and scavengers are expected.

Vicuñas and guanacos are species of wild camelids native to Argentina, Chile, Bolivia, Ecuador and Peru, where the vicuña is the national animal.

The study investigated the impacts and origins of the outbreak, which began in 2014 in San Guillermo National Park.

“This part of Argentina was once the Serengeti of wild camelids,” said corresponding author Marcela Uhart, who directs the Latin America program at the Karen C. Drayer Wildlife Health Center at UC Davis School. of Veterinary Medicine and its One Health Institute. “Now you go there and it’s empty, and whoever’s there is mangy. This disease is not new. We know about mange. It’s a common mite. But significant outbreaks occur in several wildlife species in worldwide.”

House on scabies

During the study, the authors observed signs of sarcoptic mange in a quarter of living vicuñas, a third of living guanacos, and in almost all dead vicuñas and guanacos.

Between 2013 and the start of the study in 2017, guanaco and vicuña populations declined by 95% and 98%, respectively. Almost three quarters more were lost between 2017 and 2018 alone. As of 2019, researchers could no longer find either animal during study surveys.

Sarcoptic mange is a highly contagious disease in which the mites burrow under the animal’s skin, which becomes thick, crusty, itchy and cracked. Because it becomes too difficult to move and feed, many animals starve or become easy prey.

Mites from seven vicuñas and three guanacos were collected and analyzed in the lab of co-author Janet Foley, a disease ecologist at the UC Davis School of Veterinary Medicine. They found that the mites shared the same genotype, indicating a single source and recent origin of the outbreak.

The authors traced a potential source to a government breeding incentive program that introduced llamas to areas near the park in 2009, some of which had mange, which is rarely fatal to llamas.

No infected llamas were available at the time of the study, so the authors were unable to collect mites from them to compare to the mites found on vicunas and guanacos. But the findings combine to suggest that the introduction of scabies-infected llamas may have triggered the outbreak.

Cascading consequences

In several countries, wild vicuñas are a source of income for indigenous communities, who shear the live animals for their soft and valuable fibre. Animals also play a key role in maintaining a balanced ecosystem in the vast high Andes plateau, or altiplano. Once hunted almost to extinction, the South American population is considered a conservation success story, having rebounded once strict enforcement of the fiber trade and ban on lethal shearing were enacted in the 1980s.

While global vicuña and guanaco populations are still considered healthy, the outbreak in San Guillermo is expected to have cascading consequences for local predators and scavengers.

Vicuñas and guanacos are important prey for cougars, and condors feast on leftover carcasses. Without wild herbivores on the menu, cougars may turn to local livestock for their meals unless and until wild camelid populations can rebound. Condors may also be required to forage for food outside the park, exposing them to risks such as poisoning from pesticides or lead from hunting ammunition.

“Hopefully in a few years the animals will slowly come back,” Uhart said. “But in the meantime, we don’t know what will happen to predators and scavengers because they have virtually nothing left to eat.”

One Health approach needed

The authors note that better and continued communication between the conservation and livestock sectors could have staved off the outbreak and could help prevent future illnesses.

“Several factors combined to create the perfect storm of this outbreak at great cost to the ecosystem of San Guillermo National Park,” said lead author Hebe del Valle Ferreyra, a wildlife veterinarian with the National Parks Service. in Argentina. “Animal health management, conservation and agriculture should not be viewed as opposing, incompatible and disconnected activities. A change in approach is needed that recognizes the links between all of these sectors.”

Additional co-authors on the study include Jaime Rudd and Ralph Vanstreels of UC Davis, Ana M. Martín of Universidad Católica de Córdoba in Argentina, and Emiliano Donadio of the National Council for Scientific and Technical Research (CONICET) in Argentina.

The research was supported by San Guillermo National Park, Argentina’s Administración de Parques Nacionales, UC Davis, National University of Córdoba, and the US Fish and Wildlife Service.

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