In early 2023, a troop of wild sooty mangabeys was struck by an outbreak of mpox (formerly monkeypox) — a potentially deadly disease characterized by a distinctive red rash that develops into pus-filled blisters. At the time, it was not known what triggered this particular incident, but scientists have now identified the culprit: a fire-footed rope squirrel.
The discovery, published in Nature, confirms pre-existing suspicions. But while infected rope squirrels have been linked to disease outbreaks in the past, this is the first time there has been direct proof linking the critters to a spillover event in another species.
Read More: What Is Monkeypox and Should we Still be Worried About this Virus?
What Is Mpox?
Mpox is the new name for monkeypox, so-called because it was first discovered in monkeys used for biomedical research, according to the World Health Organization.
Since then, it has been recorded in humans and is known to trigger symptoms such as skin rash, fever, headache, and swollen lymph nodes. In severe cases, the virus can lead to potentially fatal complications such as pneumonia and encephalitis (swelling of the brain).
Mpox outbreaks are caused by zoonotic spillover events in which the virus is transmitted from an animal to a person, such as through the consumption of infected meat. Once that initial event has occurred, the virus can then pass from human-to-human via close contact.
Scientists are now interested in finding the natural reservoir of mpox — that is, a species in which the virus is permanently circulating and from which outbreaks can occur.
Finding A Natural Reservoir
The outbreak that affected the mangabey community in 2023 occurred in Taï National Park, Côte d’Ivoire — a vast expanse of tropical rainforest home to chimpanzees, pygmy hippos, and 11 species of monkeys, according to the UN Environment Program. Approximately a third of the group was affected by the outbreak, and four baby monkeys died as a result.
To determine which species was responsible, researchers analyzed the remains of rodents and wildlife in the vicinity.
Using viral genome sequencing, the team linked the strain that infected the monkeys to a strain found in a dead fire-footed rope squirrel, which had been discovered approximately 1.9 miles (3 kilometers) from the monkeys’ territory 12 weeks before the outbreak.
Next, by analyzing mangabeys’ fecal remains, the researchers obtained evidence of contact between the two species: a sample collected eight weeks prior to the outbreak contained DNA from the virus and the rope squirrel.
“This represents a rare case of direct detection of interspecies transmission,” the study authors wrote.
The First Piece Of Direct Evidence
(Image Courtesy of Taï Chimpanzee Project/Carme Riutord-Fe/HIOH)
The results are not entirely surprising. The very first time the mpox virus was isolated from a wild animal, the animal in question was a rope squirrel. The rodents have also been leading suspects in previous outbreaks.
Take, for example, a 2003 incident involving U.S. prairie dog owners, which was linked to a single distributor who kept the pets alongside several species of African rodents. However, this is the first time there is direct evidence linking rope squirrels to a spillover event — and it could be an important step to curbing future outbreaks.
This is particularly important as mpox is on the rise in West and Central Africa. Data from the Democratic Republic of the Congo suggest that the number of transmissions between animals and humans has been increasing since 2010, according to the CDC.
Still, the researchers clearly point out that the results do not suggest that there are no other natural hosts or reservoirs fuelling recurrent outbreaks. Indeed, they urge future “efforts aimed at identifying other small mammal species” as “the involvement of several host species seems likely.”
This article is not offering medical advice and should be used for informational purposes only.
Read More: 5 Diseases With Surprising Animal Reservoirs — and How They Can Affect Humans
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