Deadly Bacteria Discovered in Chimps Linked to Human Illness
The finding could help save chimpanzees and shed light on similar bacteria that infect people
Scientists have discovered what they believe is a new species of bacteria causing infections that have been highly fatal in chimpanzees. The discoverers do not see it as an immediate threat to humans. But the bacterium, tentatively named Sarcina troglodytae, is in the genus Sarcina, which includes other bacteria known to cause similar illness and sometimes death in people.
The discovery, detailed February 3 in the journal Nature Communications, suggests more research is needed to understand the various species of Sarcina bacteria and their potential threats to people, the researchers say.
Because chimpanzees share 99% of our DNA, there’s often a high risk of “zoonotic transmission” between them and us. But the risk that this specific species of bacteria will hop to humans is about a 3 on a scale of 1 to 10, with 10 being “aoogah!,” says study team member Tony Goldberg, PhD, a professor of epidemiology at the University of Wisconsin-Madison.
The study was led by Leah Owens, a veterinary medical and doctoral student in Goldberg’s lab.
Similar to human infections
Since 2005, chimpanzees at the Tacugama Chimpanzee Sanctuary in Sierra Leone have suffered a disease named “epizootic neurologic and gastroenteric syndrome” (ENGS), which has killed all 56 of the chimps known to have contracted it. Symptoms include nausea, vomiting, diarrhea, and neurological deficiencies.
But the cause of the disease has been a mystery.
The discovery of Sarcina troglodytae is based on finding evidence for the novel bacteria in 13 of the chimp fatalities, including in their gastrointestinal tracts and in their brains. Further study is needed to confirm the conclusions. But taken with other research on cousins of the bacteria found in humans, the finding suggests that various Sarcina bacteria might range from relatively benign to highly virulent, Goldberg and his colleagues conclude. Spores that generate the bacteria are thought to exist in soil and may germinate seasonally, they say. ENGS cases peak in March each year.
“In light of these findings, the importance of sarcinae in human and animal clinical disease should be re-evaluated,” they write.
No human cases of ENGS have been reported, despite close contact between people and the chimps for several years. Yet there have been about 50 known Sarcina-caused illnesses in humans and is sometimes deadly. The symptoms in human cases have been similar to the symptoms in the chimpanzee infections, “but it is probably not the same species” of Sarcina, Goldberg tells me.
Concern over zoonotic diseases
History offers numerous examples of deadly human diseases that crossed the species barrier.
- The coronavirus behind the current pandemic is thought to have originated in bats, which represents a significant genetic jump to human infection.
- Malaria is thought to have arisen primarily in gorillas — more genetically similar to humans.
- People working at a primate sanctuary in Cameroon contracted monkeypox from chimpanzees, which along with bonobos are our closest relatives.
- HIV also crossed over from chimpanzees to humans, causing the devastating AIDS epidemic that continues to kill about 700,000 people around the world each year.
Zoonosis — including from bats and other mammals — is of great concern to scientists, who worry about new and emerging bacteria and viruses that could transmit between humans easily, as the current coronavirus does, but be much deadlier. One key to stopping future pandemics, experts say, is to fund research that discovers animal pathogens that could do us harm.
Bottom line on Sarcina troglodytae? No need for you to worry, and the finding offers hope for treating the disease in chimpanzees.
“This is a chimp disease that is important for chimps and for understanding animal health, conservation, and comparative medicine, but it really isn’t an alarm call about zoonotic disease,” Goldberg says. “I think everyone is so gun-shy because of Covid these days that they see zoonoses everywhere — even in places where they’re not.”
