Unprecedented Vaccination In The World Tries To Save Golden Lion Tamarin From Yellow Fever – 11/23/2020 – Science

At the end of last month, the Associação Mico-Leão-Dourado (AMLD) started implementing an unprecedented strategy in the world. This is the result of an idea that arose in 2017. The NGO from Rio de Janeiro, founded in 1992, develops strategies for the conservation of species.

This year, the virologist Marcos da Silva Freire and the primatologist Alcides Pissinatti, both veterinarians, met at a seminar on yellow fever in non-human primates at the Oswaldo Cruz Foundation (Fiocruz) in Rio de Janeiro.

Freire, PhD in Parasitic Biology, now a Scientific Advisor to Bio-Manguinhos, a Fiocruz unit, worked at the institution for 36 years in the development and manufacture of human vaccines. He specializes in yellow fever.

Pissinatti, who graduated in 1970 and is a doctor of animal biology, is director of the Center for Primatology in Rio de Janeiro (CPRJ), which was established in 1979 to study and conserve Brazilian primates.

In conversation, the two saw that it was necessary to do something about the golden lion tamarin, whose population would certainly be affected by the yellow fever outbreak that hit part of the country this year. The mosquito-borne virus mainly affected the southeast region.

It has previously been reported that entire populations of howler monkeys, marmosets and capuchin monkeys – species that are not critically endangered – have been decimated by the virus. However, nothing is known about the occurrence of the disease in Leontopithecus rosalia, the golden lion tamarin, which is, yes, threatened.

The two researchers then asked themselves: is it possible to vaccinate them?

“There was no literature on the many questions we had to answer, and our main concern was the safety of the monkeys,” says Freire.

The AMLD team also suggested the species may already be affected by yellow fever; However, it is very difficult to find dead monkeys to test the hypothesis. The animals sleep in the hollows of the trees and because they are very small – they weigh an average of 600 grams – the bodies decompose very quickly.

The suspicion was confirmed in 2018 when one of them was found dead in the forest and taken by the AMLD for exams in Rio de Janeiro. It was found that he was infected with the virus.

The damage to the species caused by the disease has been great since then. In the 1970s, there were an estimated only 200 animals in the wild. The conservation and replenishment efforts initiated at this time amounted to 3,700 in 2014. However, with the appearance of yellow fever, the number fell to 2,500, according to the 2019 AMLD census – a reduction of more than 30%.

In the Biço Reserve Poço das Antas (RJ), an ICMBio protection unit between Silva Jardim and Casimiro de Abreu that takes care of the conservation of several species, the population of the golden lion tamarin has grown from 300 to 37 individuals.

“The golden lion tamarin lives in a very specific region of the Atlantic forest of the state of Rio, in forests that are always below 500 meters and only exist there. In such a small space, the virus can be a real tragedy for the species, ”explains Luís Paulo Ferraz, geographer and executive secretary of AMLD.

In 2018, Fiocruz and CPRJ began research to pioneer the idea of ​​the vaccine, which was launched in 2017.

During this time, the researchers assessed the animals’ immune response – that is, the production of antibodies – and the safety of the vaccine. Two years later, a safe formula was achieved that creates immunity and does no harm to animals. It is the first time this has been done with primates other than humans.

So far, 58 monkeys have been vaccinated, says biologist Carlos Ruiz Miranda, professor at the State University of Norte Fluminense in Campos dos Goytacazes (RJ) and a member of the project.

The first phase of the trial program provides for the vaccination of 500 animals over a period of up to three years. Depending on the results, the number can reach 1,000.

All work is monitored and approved by the Ministry of Health and the Center for Research and Conservation of Brazilian Primates (CPB / ICMBio), which coordinates the National Action Plan for the Conservation of Primates of the Atlantic Forest and Preguiça-de-coleira.


Although they used an existing technology – the human vaccine – as a starting point, scientists had no idea whether it was safe or could induce immunity in animals. The tests were conducted on golden lion tamarin, black lion tamarin, and black-faced lion tamarin in captivity.

Basically three possibilities were tested: one with only one particle of the virus (a protein); another with inactivated virus; the third with attenuated live virus. The latter showed the best immune response in animals.

“In tamarins with golden lions it is used at a dilution of about 1/150 compared to that used in humans,” explains Freire, Fiocruz ‘virologist.

The Covid-19 pandemic delayed the start of vaccination a little. “There are no studies of coronavirus in monkeys, and we couldn’t take any chances,” said the AMLD’s executive secretary. It was then necessary to put in place procedures to avoid any risk of contamination.

To vaccinate them, the AMLD team traps the animals in the forest and takes them to the laboratory, where they are anesthetized before receiving the vaccine. They are not returned to nature until the next day.

The groups are localized by means of radio signals emitted by the collars attached to the animals, or by voice emission through playback. It is a job that requires a lot of time and patience and which AMLD field service teams have been doing for over 30 years after intensive training.

And how do you know if the vaccine has had any effect? “Between 30 and 45 days after vaccination, we will resume the animals and do a new serological test to see if antibodies have been produced, that is, if the vaccine produced the desired immune response,” explains Miranda. This will happen next week.

If the experiment is successful, the first vaccinated animals will be moved to the areas most affected by yellow fever and where the mosquitoes transmitted by the virus circulate. This will solve one of the main problems affecting these populations today.

Again, the greatest threat to the species will be the destruction of forests in the area.

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