Seven employees of an Oregon zoo contracted tuberculosis from three elephants in their care in 2013, the U.S. Centers for Disease Control and Prevention said on Friday, NBC News reported.
The staff members at the Oregon Zoo in Portland were infected with a latent form of the respiratory illness and therefore displayed no symptoms and were not contagious, a report published by the CDC said.
The report was issued two days after a U.S. judge ordered the CDC to release documents on tuberculosis in elephants to animal-rights group People for the Ethical Treatment of Animals. Oregon health officials said the timing of the report was unrelated to the lawsuit.
The CDC report on the outbreak pointed to a lack of research about tuberculosis in elephants. It also called for improved screening to detect the disease because the present method of detection - taking cultures - may miss some cases or result in false positives.
The outbreak was identified in May 2013 when a routine annual check of elephants found that a 20-year-old bull named Rama was infected.