Recent chimpanzee deaths caused by environmental pathogen

Project Chimps recently shared the sad news of two deaths of chimpanzees at its sanctuary in Morganton, Georgia. The organization fears there may be more deaths to follow as the cause is now known to be the bacteria Yersinia.

Executive Director Ali Crumpacker reports: “My team has been under a tremendous amount of stress to provide supportive care for the chimps who have fallen ill while grieving for those we have lost. The outpouring of support we have received from the community has sincerely helped boost morale.”

It is not uncommon for the chimpanzees to catch a seasonal cold in the winter, much like the human population. When the first signs of this recent illness began, the symptoms were mild. Initially, supportive care and attention to ensure the affected chimps had access to plenty of fluids (Powerade and Gatorade) and their favorite food items, was enough for the chimps to rebound after a few days. Samples were taken from cooperative chimps and sent to labs for testing, but all tests came back negative. 

As symptoms increased among the chimps, some did not respond to the basic supportive care and refused to take medications. In these cases, the medical team assembled and treated the chimps individually, providing IV fluids and medications, running blood panels, x-rays, and other diagnostic tests. In most cases, the chimps who received these treatments immediately improved and made a full recovery within several days. All the tests that were run were coming back negative, with no clear indication on the cause of the problems.

On February 2nd, the sanctuary humanely euthanized an 18-year-old chimpanzee named Tabby who failed to revive from her veterinary procedure. Post-mortem testing and exams indicated that Tabby had an underlying issue with her liver that had not been seen previously. Additional cultures received several days later indicated she had been infected with the Yersinia bacteria.

Yersinia is a genus of bacteria that is widespread in nature. According to the CDC, 117,000 humans are infected with Yersinia annually (https://www.cdc.gov/yersinia/faq.html). Symptoms of infection may not appear for as long as two weeks after exposure.

Additional fresh samples were immediately collected from other sick chimps and sent to the lab for testing, but results were negative for Yersinia. The search for the ailment afflicting the chimps continued.

On Feb 21, the sanctuary humanely euthanized 19-year-old Stirlene; he had received two rounds of treatments with intravenous fluids and medications but continued to decline in health. Stirlene had received his routine physical less than a year before, when he was found to be in good physical health and was noted to have a heart arrhythmia. Cardiovascular deaths are the leading cause of mortality in captive great apes and it was presumed that the unknown illness was impacting Stirlene’s heart, thus creating additional stress on his body.

Subsequent tests showed that, despite prior tests that were negative for Yersinia, Stirlene in fact had the same bacterial infection as Tabby.

Two other chimps remain in critical condition at this time — Rusty, 37, and Genesis, 18. Both have received hands-on support with IV fluids and additional antibiotics that will target a Yersinia infection. Rosemary, 29 has been closely monitored and will be examined tomorrow.

Yersinia is transmitted mainly by ingestion of food or water contaminated with feces from infected birds and rodents, which are considered to be the main natural reservoirs of this pathogen. As the chimpanzees have access to open-air yards surrounded by forest, the origin of this strain of Yersinia may never be identified.

As part of regular facility-safety procedures, rodent prevention protocols keep populations in check and water samples are routinely tested and treated as needed. Project Chimps’ open-air habitat is inspected by staff daily. The chimpanzees afflicted had been living in this environment for 3-6 years. The facility passed a USDA inspection on Dec 1, 2020, and an independent welfare review on Oct 8, 2022.

Crumpacker states, “We will continue our efforts to identify the source, and control the spread of Yersinia in the chimp population. The chimps will be prescribed a 10-day course of antibiotics for all of the chimps, regardless of symptoms, in an effort to fully eradicate the bacteria.” The chimpanzees will receive their medications disguised in peanut butter sandwiches, a favorite treat for most of them.

The cost of caring for each chimpanzee at Project Chimps is approximately $30,000 per year. Hands-on exams for the critically ill chimps cost $5,000 each time. The cost of the current proactive treatment plan will be $150 per chimp, or approximately $15,000 to treat all 97.

Project Chimps is a sanctuary that operates under strict “protected contact” protocols, meaning that there is no direct contact between chimpanzees and humans; and all staff are trained and provided with proper safety gear to prevent zoonotic cross-contamination.