Milwaukee County Zoo officials on Thursday, June 7 said necropsy examinations have revealed two western lowland gorillas, Cassius and Naku, who died in April, died of gastrointestinal infections - believed to be secondary to an E. coli possibly associated with the exhibit's water system.
According to a news release from zoo officials, all animals, including gorillas and humans, have large amounts of healthy E. coli lining the intestines. Some variants of E. coli are known to cause intestinal damage and disease.
They noted that the water systems in both the gorilla and bonobo areas have been disinfected. They said water supplied to the public was not affected.
Zoo officials said new research into "biofilms" indicates water systems can become sources of contamination. Therefore, disinfection of water systems is common practice in such places as dairies and human hospitals.
New protocols are being implemented to disinfect produce at the zoo, which can be another source of E. coli.
Cassius was 31 and died on April 12. Naku was 17 and died on April 30.
Cassius and Naku left behind baby Zahra - now an orphan. She was born at the zoo in September. Zookeepers are now helping raise her.