A recent outbreak of monkeypox among sooty mangabeys in Côte d’Ivoire’s Taï National Park has been directly linked to transmission from a fire-footed rope squirrel. This marks the first documented case of monkeypox jumping between animal species in a natural setting, providing critical insights into how the virus spreads and potentially spills over into human populations.
The Outbreak and Initial Findings
In early 2023, approximately one-third of the park’s sooty mangabey population developed symptoms of monkeypox, including characteristic skin lesions. Tragically, four infant monkeys died during the outbreak. Researchers, publishing in Nature on February 11, traced the origin to a single fire-footed rope squirrel (Funisciurus pyrropus) found dead just 12 weeks before the outbreak began.
The significance of this finding is clear: monkeypox isn’t just a human concern; it’s an active disease cycle within wildlife. Understanding these animal reservoirs is crucial because most human cases originate from zoonotic spillover events – where a virus jumps from animals to people.
Rodents as Reservoirs: A Long-Suspected Link
For years, African rodents, particularly rope squirrels, have been suspected as primary reservoirs for the monkeypox virus. Previous research had already identified the virus in Thomas’s rope squirrels and even in museum specimens dating back to 1899. However, direct evidence of live transmission in the wild was lacking.
The Taï National Park has seen sporadic monkeypox outbreaks in primates since 2012, including cases in sooty mangabeys and chimpanzees. The key mystery was where these animals were getting infected from. Extensive monitoring, including testing over 700 rodents, finally yielded the answer.
Direct Evidence: DNA and Viral Tracing
The team analyzed genetic material from both the infected squirrel and the mangabeys. Results showed a close but not identical match, suggesting that the squirrel wasn’t the only source, but likely a recent transmission event. Further analysis of fecal samples from the mangabeys confirmed the link: two samples tested positive for rope squirrel DNA and one of those also carried the monkeypox virus, confirming recent consumption. Video evidence from 2014 had previously shown a mangabey consuming a rope squirrel, making the recent outbreak even more conclusive.
Implications for Human Health
This research has immediate implications for public health. Knowing that fire-footed squirrels carry the virus allows for targeted prevention measures in areas where humans interact with these animals. Officials may advise those working near squirrel habitats to use protective gear or practice thorough hygiene.
“Pinpointing which animals carry the virus can help guide prevention measures that protect people from getting infected,” says Clement Meseko, a veterinarian and virologist at the National Veterinary Research Institute in Nigeria.
The study reinforces the need for ongoing wildlife monitoring. Other rodent species likely also carry the virus, meaning additional threats remain unidentified. The cycle of monkeypox in the wild is now more clearly defined, but the work to understand and control its spread is far from over.
The findings underscore the importance of One Health approaches—recognizing the interconnectedness of animal, human, and environmental health—to effectively prevent future outbreaks.
