Mountain gorillas that live in Rwanda’s Volcanoes National Park have frequent encounters with humans. On any given day, animals might bump into tourists with their smartphones, biologists taking stool samples, or veterinarians administering antibiotics.
So when the coronavirus began to spread around the world in early 2020, experts feared that people could inadvertently transmit the virus to the endangered monkeys, which are vulnerable to a range of human pathogens.
“In the past, other human viruses have caused respiratory illness in gorillas,” said Dr. Kirsten Gilardi, executive director of Gorilla Doctors, an international team of veterinarians who care for gorillas.
“We were very concerned, thinking about what we would do if the virus got to mountain gorillas,” Gilardi said.
In March 2020, in an effort to protect animals, Rwanda temporarily closed Volcanoes National Park. When it reopened a few months later, it had taken strict new precautions, such as requiring tourists and researchers to wear masks and keep their distance from animals. Those rules, plus the general reduction in tourism, meant that the park’s gorillas had fewer close encounters with humans during the pandemic, she said.
And so far there have been no signs of coronavirus among the gorillas. In trying to control an extraordinary health threat, however, the authorities may have also alleviated a more everyday one: the routine transmission of respiratory diseases from humans to great apes. Since March 2020, the number of respiratory disease outbreaks among the park’s gorillas has dropped from 5.4 a year to 1.6 on average.
“The bottom line is that these best practice measures to protect great ape populations appear to be working,” said Gilardi, who reported the findings in the journal Nature this month. The report was co-written with Prosper Uwingeli, Chief Guardian of Volcanoes Park.
The analysis is preliminary, and the researchers cannot prove that the gorillas’ health improved because humans kept their distance. But the findings suggest that even after the pandemic subsides, stricter controls may be needed to help protect endangered primates from human disease, the scientists said.
“The same kinds of things that can protect wild animals that are susceptible to Covid can protect them from other human pathogens,” said Thomas Gillespie, a disease ecologist at Emory University who works frequently with wild primates but was not involved in the study.
Just over 1,000 mountain gorillas remain in the wild, split between national parks in Rwanda, Uganda and the Democratic Republic of Congo. Many gorillas were deliberately habituated to humans to facilitate research and ecotourism.
Monkeys face a variety of threats, such as poaching and habitat loss, but respiratory disease is also a major concern and a leading cause of death among them.
Outbreaks of respiratory disease have become common among animals.
“They happen regularly,” said Gilardi, who is also a wildlife veterinarian at the University of California at Davis. “And we don’t always know what causes them.”
Bacteria and viruses circulate naturally among gorillas and other primates, some of which can cause respiratory infections. But scientists have also documented several cases where human pathogens, including rhinoviruses and coronaviruses responsible for common colds, managed to reach the great apes.
In many cases, respiratory viruses can cause relatively mild and known symptoms in infected gorillas.
“They cough, they sneeze, they have a runny nose, they may have swollen eyes, refuse food, become lethargic, not want to get out of bed in the morning,” Gilardi said. (Gorillas make and sleep in nocturnal nests.) “They look and act like we do when we have an upper respiratory infection.”
But these outbreaks can sometimes cause serious illness, such as pneumonia, or even death. In 2009, a human respiratory virus struck 11 of 12 gorillas in a family group in Rwanda. Five animals required veterinary care and two others, including a baby, died.
To curb this transfer of disease between species, the International Union for Conservation of Nature issued a set of guidelines in 2015 for scientists, tourists and others who may have contact with great apes. Recommendations include staying at least seven meters away from animals and wearing a face mask when closer. (Gilardi and Gillespie participated in authoring the guidelines.)
But not all countries have adopted or implemented the recommendations, according to Gillespie. Until the pandemic arrived.
“The pandemic really got everyone on board fully,” he said.
Volcanoes National Park now requires tourists, staff, researchers and others who approach gorillas to wear masks, which was not mandatory before. It also requires people to stay nearly ten meters away from animals. Tourism has not yet fully resumed, Gilardi said.
The difference was noticeable, she said: “We’re not seeing as many respiratory illnesses today as we did in years past.”
Other great ape sites are collecting data on how and whether infectious disease incidence has changed since the beginning of the coronavirus pandemic, Gillespie said. And the same precautions can be used to protect a wide range of wild primates, he added.
“Many of these practices can be successfully applied to other endangered and endangered species,” he explained. “People need to do these things, with or without Covid.”
Translated by Luiz Roberto M. Gonçalves.
