CDC publishes Health Department report on elephant-to-human tuberculosis transmission

January 15, 2016

Multnomah County Health Department experts who track disease often publish reports on their investigations to increase public awareness and share what they’ve learned.

On Jan. 8, their report on tuberculosis at the Oregon Zoo in Portland was published in one of the largest medical journals in the country, the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.

“Diagnosis of Tuberculosis in Three Zoo Elephants and a Human Contact — Oregon, 2013” -- summarized an investigation into the transmission of tuberculosis from elephants to eight people.

Multnomah County Health Department Research Scientist Amy Zlot led the lengthy investigation along with Deputy Health Officer Dr. Jennifer Vines. Community Health Nurse Laura Nystrom, now retired, and former Health Officer Justin Denny, now at OHSU, also contributed, along with state officials.

Epidemiologist Amy Zlot, left, and Dr. Jennifer Vines led the investigation.

Infectious tuberculosis in our community is rare, said Dr. Vines. The Health Department carefully identifies anyone exposed to make sure they get testing and treatment. It usually spreads to others by close and prolonged contact, for example household members. Because of antibiotics, the disease is preventable and curable.

Tuberculosis can also infect elephants. It was first discovered in the animals in 1996, Zlot said. The first elephant-to-human transmission was recorded in 2009. Zoos have been required to routinely test elephants for the bacteria ever since. There have been more than 60 confirmed cases of tuberculosis in elephants nationwide.

In May 2013, Oregon Zoo employees reported to the Health Department that an elephant’s trunk test was positive for active tuberculosis.

County staff worked with zoo staff, the state veterinarian and the CDC, which traced the genotype of the tuberculosis strain.

Between May 2013 and May 2014, a total of three elephants at the zoo tested positive for active tuberculosis. In response, Zlot and her team spent nearly two years identifying, contacting and testing 119 people who had been in both close and casual contact with the sick elephants. They found that those with close and prolonged contact were at risk for getting latent tuberculosis.

"There has been no evidence of risk to the general public,'' Vines said.

The three elephants were isolated and treated to prevent infection of other animals and humans. The people with latent tuberculosis were offered treatment with antibiotics.

Vines worked with the zoo staff to put in place additional protective measures for staff, volunteers and the public.They published the report to add to the rather slender body of knowledge about elephants, people and tb. The most important thing they said, was showing that the risk to the general public was nearly zero.

"We did a good job,'' Zlot said. "We worked to protect our community.''