{"id":2206582,"date":"2026-08-08T18:00:27","date_gmt":"2026-08-08T17:00:27","guid":{"rendered":"https:\/\/focusingonwildlife.com\/news\/?p=2206582"},"modified":"2026-08-08T10:03:04","modified_gmt":"2026-08-08T09:03:04","slug":"researchers-find-priority-zones-for-yellow-fever-vaccination-of-golden-lion-tamarins","status":"publish","type":"post","link":"https:\/\/focusingonwildlife.com\/news\/researchers-find-priority-zones-for-yellow-fever-vaccination-of-golden-lion-tamarins\/","title":{"rendered":"Researchers find \u2018priority zones\u2019 for yellow fever vaccination of golden lion tamarins"},"content":{"rendered":"

After a two-hour drive from the airport in Rio de Janeiro, you reach a special park dedicated to a special animal in Brazil\u2019s Atlantic Forest. There, you can take a\u00a0guided tour\u00a0through the green and perhaps catch a glimpse of vibrant orange: The pelage or furry coat of one of this region\u2019s most famous resident, the golden lion tamarin.<\/p>\n

Between 2017 and 2019, a yellow fever epidemic killed roughly 30% of the population,\u00a0leaving only 2,500 alive. This small, endangered monkey, which nearly went extinct in the 1970s, is relegated to fragmented forests in the state of Rio de Janeiro, about\u00a02% of their original territory, according to conservation nonprofit Save the Golden Lion Tamarin.<\/p>\n

But the tamarins (Leontopithecus rosalia<\/em>) have made a significant recovery,\u00a0rebounding to roughly 4,800 individuals according to a 2023 census.<\/p>\n

To better prepare for a possible outbreak in the future, a group of researchers wanted to find out how different environmental factors affected yellow fever transmission between tamarins.\u00a0Their research identified high-risk areas, which could guide conservationists aiming to vaccinate the population against future epidemics.<\/p>\n

\"The
The golden lion tamarin, an endangered species, is found exclusively in Brazil\u2019s Atlantic Forest, a seriously threatened biodiversity hotspot: only 7%-12% remains. Image by Themium via\u00a0Wikimedia Commons\u00a0(CC0 1.0).<\/figcaption><\/figure>\n

Mapping an outbreak<\/h2>\n

Researchers compared mortality data from 2014-2016, before yellow fever struck, with\u00a0more than 1,000 deaths\u00a0that occurred during the outbreak in 2017-2019, information that was gathered by the nonprofit\u00a0Golden Lion Tamarin Association\u00a0(known in Brazil as Associa\u00e7\u00e3o Mico-Le\u00e3o-Dourado). They then looked at how a series of variables in the environment itself, including human population, forest cover and habitat connectivity, might be linked to the deaths.<\/p>\n

Notably, they found that areas with higher human density had significantly lower tamarin survival rates during the outbreak. This comes down to cross-species transmission, said Maxime Pierron, a University of Strasbourg ecologist and first author on the study. Yellow fever is a zoonotic disease: It can infect both humans and animals, specifically primates.<\/p>\n

\u201cWe can both get [yellow fever], so it\u2019s easy \u2026 to share it,\u201d he said.<\/p>\n

Habitat connectivity had a similar effect. Though it improved survival before the outbreak began, that outcome flipped once the epidemic got underway.<\/p>\n

\u201c[Connectivity] reduces mortality because it improves the gene flow and it allows primates to evade threats more easily, so it\u2019s great,\u201d Pierron said. \u201cBut during an outbreak, it turns out that this also facilitates the movements of mosquitoes that are infected with yellow fever,\u201d which increases transmission, he added. The researchers found yellow fever caused more deaths in forests that were better connected.<\/p>\n

\"Connected
Connected habitat is crucial for wildlife survival, but a new study found that during the 2017-2019 yellow fever outbreak, more tamarins died in connected forest areas and areas where there were more people to pass it to them. Image by Alex Popovkin via\u00a0Wikimedia Commons\u00a0(CC BY 2.0).<\/figcaption><\/figure>\n

The value of connectivity<\/h2>\n

Despite this, Pierron warned that the findings should not be interpreted as an argument against reforestation and restoring or relinking fragmented habitat.<\/p>\n

\u201cReforestation is both welcome and urgently needed around the world,\u201d he wrote in an email to Mongabay, adding that \u201cin this context, it is essential to combine reforestation with landscape-informed disease monitoring and to integrate disease ecology into conservation planning.\u201d<\/p>\n

Connected habitat could help the tamarin population recover from a future outbreak, Carlos Ruiz-Miranda, co-author of the study and board president of the Golden Lion Tamarin Association, told Mongabay in a voice message.<\/p>\n

\u201cThe more connected the habitat is, the faster or more likely the recovery and recolonization,\u201d he said.<\/p>\n

University of Wisconsin-Madison anthropologist\u00a0Karen Strier, who has studied monkeys in the Atlantic Forest since 1982, said the research brought to mind an old ecological debate between scientists known as SLOSS (single large or several small): a disagreement on the ideal structure of wildlife reserves. One of the arguments against larger areas, she said, was that diseases within them could spread.<\/p>\n

\u201cConnectivity is important, but it has some costs too, and I think it\u2019s important to be aware of those costs,\u201d Strier said. \u201cNot because we should stop trying to connect habitats, but so that we can think as [the paper\u2019s authors] do about how to mitigate the risks.\u201d<\/p>\n

\"The
The golden lion tamarin is one of Brazil\u2019s most iconic conservation success stories, but yellow fever seriously impacted the population nearly 10 years ago. Image by Jeroen Kransen via\u00a0Wikimedia Commons\u00a0(CC BY-SA 2.0).<\/figcaption><\/figure>\n

Vaccination nation<\/h2>\n

A key part of that mitigation is vaccinating tamarins against yellow fever. AMLD staff\u00a0began\u00a0that process in 2020. They\u2019ve immunized just over 500 individuals so far, according to Ruiz-Miranda.<\/p>\n

According to Pierron, \u201cdeath risk during the outbreak can serve as a proxy of transmission risk.\u201d In other words, based on where deaths occurred during the outbreak, scientists can predict areas where the disease might spread more easily in the future. These high-risk areas are \u201cpriority zones\u201d for vaccination.<\/p>\n

The team has already immunized some individuals from most populations, Ruiz-Miranda said, and plans to vaccinate individuals from the rest in the future. To vaccinate the monkeys, a team captures them and brings them to a field laboratory, he said, where they sedate the animals. They collect hair samples for DNA studies and take measurements before injecting the vaccine. The team tattoos numbers on each animal\u2019s inner thigh to make sure they don\u2019t vaccinate the same individual twice, he said, and then they release them where they were found.<\/p>\n

According to Marcos da Silva Freire, a scientific advisor at Brazil\u2019s Oswaldo Cruz Foundation, who helped develop the yellow fever vaccine for golden lion tamarins, the immunization campaign should continue indefinitely. Though vaccinated animals will eventually die, keeping at least a percentage of the population protected helps \u201cavoid some disaster with yellow fever reemergence in the region,\u201d he said.<\/p>\n

\"Golden
Golden lion tamarins in the S\u00e3o Paulo Zoo in Brazil. Image by Wilfredor via Wikimedia Commons (CC BY-SA 4.0).<\/figcaption><\/figure>\n
<\/figure>\n

Citations<\/h2>\n

Pierron, M., Ponchon, A., Ruiz\u2010Miranda, C. R., Martins, A., Sueur, C., & Romano, V. (2026). When conservation meets contagion: Mapping yellow fever risk to guide vaccination in an endangered primate.\u00a0Journal of Applied Ecology<\/em>,\u00a063<\/em>(6). doi:10.1111\/1365-2664.70463<\/a><\/p>\n

Dietz, J. M., Mickelberg, J., Traylor\u2010Holzer, K., Martins, A. F., Souza, M. N., & Hankerson, S. J. (2024). Golden lion tamarin metapopulation dynamics five years after heavy losses to yellow fever.\u00a0American Journal of Primatology<\/em>,\u00a086<\/em>(7). doi:10.1002\/ajp.23635<\/a><\/p>\n

Dietz, J. M., Hankerson, S. J., Alexandre, B. R., Henry, M. D., Martins, A. F., Ferraz, L. P., & Ruiz-Miranda, C. R. (2019). Yellow fever in Brazil threatens successful recovery of endangered golden lion tamarins.\u00a0Scientific Reports<\/em>,\u00a09<\/em>(1). doi:10.1038\/s41598-019-49199-6<\/a><\/p>\n

This article<\/a> by Alex Megerle was first published by Mongabay on 30 July 2026. Lead Image: Two golden lion tamarins in Brazil. Image by Henrique Bitencourt via Wikimedia Commons (CC BY-SA 4.0).<\/em><\/p>\n

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