A new study published in Scientific Reports shows that coughs and colds spread rapidly in wild mountain gorilla populations, but it seems unlikely that they will spread between adjacent groups. Diseases, especially respiratory infections, are one of the biggest threats to ape protection. Because humans and apes are so closely related, apes can be infected with many of the same diseases as we do. However, relatively mild respiratory infections in humans can have significant consequences in apes such as gorillas and chimpanzees, where the common cold or flu can be fatal.
Scientists from the Diane-Fosse Gorilla Foundation studied 15 outbreaks of respiratory disease over the past 17 years to understand how the disease spreads among mountain gorilla populations in Rwanda's Volcanoes National Park. These findings will help shape future conservation strategies.
Dr Robin Morrison, lead author of the study, said: "If we can better understand how disease has spread in the past, we can better prepare and respond to future outbreaks. ”
The study authors found that close contact and strong social relationships within the gorilla population allowed respiratory diseases to spread rapidly among group members. Moreover, the pattern of transmission cannot be predicted by the social network of a group. In one outbreak, 45 of the 46 group members began coughing in just three days.
These results differ from earlier studies of chimpanzees, in which chimpanzee social organizations are more fragmented, resulting in slower overall transmission, and researchers are able to predict disease spread based on chimpanzees' social networks.
There is some good news for this endangered gorilla population. The researchers found that the chances of the infection spreading between neighboring groups were limited.
Yvonne mushimiyimana, co-author of the project, said: "The outbreaks we investigated all seem to stay within one group rather than spread between the wider groups. Gorillas interact fairly little, and when they do, they tend to keep their distance, rarely approaching within a critical 1-2 meter distance. "
This apathy to neighboring groups may actually help protect a wider group by limiting the wider spread of these infections. But if gorilla populations don't infect each other, how did these outbreaks come about? Other studies of wild apes have shown that outbreaks of respiratory disease are caused almost entirely by pathogens in humans. In Uganda, two adjacent chimpanzee communities began to show signs of respiratory infections at the same time, but genetic analysis found that these infections were caused by two completely different human pathogens. The findings surprised the scientists, who expected the infection to have spread between the two chimpanzee communities. Instead, the analysis revealed that both infections were transmitted independently from humans.
Morrison said: "Our best guess is that these infections in mountain gorillas come from humans. This does highlight the importance of ongoing efforts to reduce the exposure of wild gorillas to human diseases in research, tourism and conservation activities. In the context of a global pandemic, getting vaccinated, wearing masks and staying adequate distance are more important than ever. ”
Identifying strategies to limit the spread of the disease is the focus of conservation efforts. Different diseases may have very different routes of transmission, but this study helps scientists understand that future disease outbreaks with similar transmission dynamics may spread through gorilla populations.
Dr Tara Stoinsky, President and Chief Scientific Officer of the Fersa Foundation, said: "The results of this study show that because respiratory diseases spread rapidly within gorilla populations and there is much less transmission between groups, strategies to prevent initial spread to one group may be most effective. "For covid-19 and other human respiratory pathogens, this means preventing the disease from being introduced to gorillas for the first time from humans."
"Although this study was done long before covid-19, the current pandemic highlights that minimizing the transmission routes of ape disease is more important than ever, posing a risk to both wild gorillas and humans," Stoinsky said. ”