Recovery of the gold lion tamarin threatened by a yellow fever epidemic

Three years before the arrival of COVID-19, another type of virus was making its way into southeastern Brazil. It was the start of a serious yellow fever epidemic. That disease, transmitted by mosquitoes, resulted in the deaths of 745 people between 2016 and 2018. During that time, there was devastation in the monkey populations of the region. Brazilian authorities counted more than 4,575 monkeys dead from yellow fever, but some biologists put the number of victims at more than 90,000. That epidemic joins the leading threats that currently weigh on the primates of Brazil’s Atlantic Rainforest.

The origin of the virus

The yellow fever virus arrived in the Americas more than 450 years ago on ships sailing from Africa. African monkeys get along very well with the virus, but American monkeys do not. A number of species of Neotropical primates (those living in Central America and South America) are very sensitive to this virus. In certain places, local populations have been almost completely eradicated.

The golden lion tamarin, a success threatened

The golden lion tamarin came very close to disappearing in the 1970s, when there were barely 200 left in the wild. At the time, it was subject to poaching, and its natural habitat was being reduced to a few scattered plots. Desperate recovery measures were launched: creation of the Poço das Antas Biological Reserve (50 km²), the planting of trees, the increase in protected areas, the reintroduction of golden lion tamarins from captivity, and the creation of a non-governmental organization to help maintain the population over the long term.

The results were impressive. In 2014, about 40 years on, it was estimated that 3,700 golden lion tamarins were living in a territory of at least 400 km² of protected forest. But today, all the work accomplished is threatened by the ravages that yellow fever has brought about. According to 2018 estimates, only 2,516 individuals were left. The virus has caused a 32 percent drop in the population. A number of family groups have been completely eradicated. In some spots, like the Poço das Antas Biological Reserve, the golden lion tamarin population plunged by 70 percent.

The hope is in the vaccine

Since, in the case of humans, a vaccine already exists for this virus, scientists concluded that the best option was to test it on golden lion tamarins. That project was feasible because the species occupies a relatively restricted area. Tests were first carried out on golden lion tamarins in captivity with diluted doses of the human vaccine, and then a vaccination protocol was presented to the authorities. The scientific team was ready to go to work. All that was needed was official authorizations, but it was right then that COVID-19 reached Brazil.

That misfortune set the vaccination program back seven months. There was a feeling of urgency in the scientific team, who worried about the negative effects such a delay might have on the survival of the species.

After the lifting of the lockdown, health measures had to be put in place, as much to protect workers as to prevent contaminating the golden lion tamarins. It was out of the question to take risks, since we still don’t know if COVID-19 is transmittable to this primate. The aim is to vaccinate 500 golden lion tamarins as a means of ensuring the long-term survival of this endangered species.

Let’s remain vigilant

These events demonstrate just how much the survival of an endangered species must never be taken for granted. The recovery of golden lion tamarin populations is considered a great success, and is often held up as an example. In spite of everything, scientific teams are at this moment very worried about the future of the species, and efforts have been intensified to deal with this crisis. A lengthy process is involved, one that will require a lot more effort and resources.

Let’s remain vigilant, because we don’t always know where the next threat will come from.

To learn more:

• Pandemic threatens half-century of efforts to protect rare monkeys
• Yellow fever in Brazil threatens successful recovery of endangered golden lion tamarins.
• Brazilian Forests Fall Silent as Yellow Fever Decimates Threatened Monkeys