Mountain gorillas are highly susceptible to human-transmitted respiratory viruses. Respiratory illnesses are usually widespread among gorillas, and are the second leading cause of death in wild, human-habituated populations.
According to a “Correspondence” report recently published in the journal Nature, respiratory illness outbreaks among wild mountain gorillas in the Volcanoes National Park in Rwanda have significantly declined since the beginning of the COVID-19 pandemic.
In the five years prior to March 2020, the Volcanoes National Park reported 5.4 respiratory illness outbreaks in gorilla family groups annually. However, from March 2020 to December 2021, the gorilla populations averaged only 1.6 respiratory illness outbreaks. Fortunately, no traces of SARS-CoV-2 have been detected until now in samples collected from gorillas with such illnesses.
This massive decline in respiratory outbreaks during the pandemic is associated with an overall reduction in the number of people coming close to the gorillas, and with the additional health protection measures taken to reduce disease transmission from humans to gorillas, such as mask wearing and social distancing.
“Respiratory illness outbreaks are common in wild, human-habituated mountain gorillas, and considering that gorillas are susceptible to SARS-CoV-2, this preliminary analysis is such a welcome finding,” said study co-author Kirsten Gilardi, the executive director and chief veterinary officer for Gorilla Doctors, and the director of the Karen C. Drayer Wildlife Health Center at the UC Davis School of Veterinary Medicine. “It is a testament to the early and decisive action of park authorities to help protect mountain gorillas and humans.”
Professor Gilardi and her colleagues argue that some of the key factors leading to this reduction in gorilla respiratory illness outbreaks include the temporary suspension of gorilla ecotourism, as well as the mask mandate issued by the Rwanda Development Board, and the social distancing rules aiming to keep a minimum of 10 meters between humans and gorillas.
According to Jean Bosco Noheri, a field veterinarian at Gorilla Doctors, “variation in pathogenicity of viruses, gorilla group dynamics, climate conditions and a variety of other factors may also be impacting the decrease in respiratory illness outbreaks we have seen.”
The research findings stress the important of best practice measures that minimize human disease transmission to great apes. Considering the increased contagiousness of the Omicron variant and the return of gorilla ecotourism, Gorilla Doctors and the Rwanda Development Board have recommended these measures to be made permanent.