Researchers have identified a bacterium that they believe is responsible for a “new and always fatal” illness that has been killing chimpanzees in Sierra Leone, USA Today reports. The disease—Epizootic Neurologic and Gastroenteric Syndrome, or ENGS—has killed at least 53 chimps at the Tacugama Chimpanzee Sanctuary, per the New York Post. The deaths occurred between 2005 and 2018. “It was not subtle,” researcher Tony Goldberg of the University of Wisconsin tells Science. “The chimpanzees would stagger and stumble, vomit, and have diarrhea. Sometimes they’d go to bed healthy and be dead in the morning.” The likely cause of the condition is a clover-shaped bacterium dubbed Sarcina troglodytae, which was found in tissue samples from 13 chimps that died.
The bacterium was not found in samples from healthy apes. Leah Owens, a graduate student working with Goldberg, noticed the bacterium in the brain tissue of a dead chimp. “Late at night, I was looking through the microscope and I saw this really weird-looking cubic structure,” she tells Science. ENGS has not been found in a human, but the transmission of diseases—such as Ebola and HIV—between apes and people is common, USA Today notes. “There are very few pathogens that infect chimpanzees without infecting humans and very few pathogens that infect humans without infecting chimpanzees,” Goldberg tells the paper. And, per the Post, a bacterium related to Sarcina troglodytae has caused a rare gastrointestinal disease in humans. (Read more chimpanzees stories.)