Posted on July 29, 2016 by Stephanie Stevens, MA
Just before entering veterinary school, Michelle found a summer job at a wildlife refuge. She spent most of her time caring for Asian and African elephants until she came down with what she thought was the flu. Had she been around anyone who was sick? Had she travelled anywhere recently? Michelle’s doctor needed to ask a lot of questions to get to the bottom of her illness. He knew her diabetes left her more susceptible to some infections. Then he asked where she worked. A wildlife refuge. “Could this be a disease she caught from an animal?” he wondered. Michelle’s doctor took blood samples and conducted a Mantoux tuberculin skin test (TST), which came back positive. Michelle reported that she had had a negative TST when she had returned from her trip to Africa two years ago. Additional tests would be needed to confirm TB disease. Dr. Smith ordered a chest x-ray which showed white spots on Michelle’s lungs. Additional tests of Michelle’s sputum confirmed she had active TB, or TB disease.
Studies have shown that about 12% of Asian elephants and 2% of African elephants in captivity are infected with tuberculosis (TB), which is caused by a germ called Mycobacterium tuberculosis. Studies have also documented the transmission of the bacteria from elephants to humans working in close proximity to the animals.
Indeed, an elephant who had arrived at the refuge from an exotic animal farm and was staying in the quarantine barn tested positive for TB. In Michelle’s case, she may have become infected from direct transmission when working with the elephants or through indirect transmission of the TB bacteria, which could have become airborne during routine barn maintenance such as sweeping waste or pressure washing. The practice of pressure washing might also have created a contaminated mist that could have lingered in an enclosed barn for hours. Although workers typically wore respirators when working inside the barn, air could have flowed between the barn and the adjacent office where employees did not wear respirators.
Other workers who were in contact with the TB-infected elephant were given the tuberculin skin test and three also tested positive. These other workers, who did not have symptoms, were infected with the TB bacteria but were not sick—known as a latent infection. Partly because of Michelle’s diabetes, her immune system was not able to fight the bacteria; the TB bacteria became active, multiplied, and caused TB disease.
Some practices or policies that could be implemented to help reduce workers’ exposure to TB at a wildlife refuge, zoo, or circus that houses elephants include the following:
Test all elephants in the United States annually for TB according to USDA guidelines.
Treat all elephants with TB disease as soon as possible and continue through the full course of treatment to reduce exposures to employees.
Provide general TB training during working hours to all employees when they are hired and then again each year to ensure a thorough understanding of the disease, its symptoms, its transmission, and ways to prevent it. General training and education materials can be found on the CDC TB website.
Conduct at least annual TST tests for employees. Ensure that employees who test positive for TB receive a prompt medical evaluation and that employees who have tested positive for TB in the past but do not have active TB disease undergo a medical evaluation for symptoms of TB disease each year.
If an elephant is diagnosed with TB, keep the windows and doors of the barn open as much as possible to increase ventilation.
Turn on the exhaust fans, open all barn doors and allow the barn to “air out” for a considerable length of time (15 minutes or more, depending upon barn design/configuration) before employees enter the elephant stall area. The exhaust fans should remain on during and after potential aerosol-generating activities like power washing, and when elephants and employees are present in the elephant stall area.
Wear respiratory protection (N95 filtering facepiece respirator or greater) when working within 25 feet of an elephant with known or suspected TB disease or within the elephant stall area, regardless of whether the ventilation systems are functioning or elephants are present. It is important to note that the 25-foot distance is recommended in the absence of other data; no evidence is available to define a safe distance from a TB-infected elephant. Protection greater than an N95 filtering facepiece respirator (e.g., a full-facepiece elastomeric respirator or powered air purifying respirator [PAPR]) should be considered for aerosol-generating procedures such as high-pressure washing in the barn. Ensure that respirator use is in conformance with the OSHA respiratory protection standard.
Wear disposable coveralls such as Tyvek® on top of the work uniform during aerosol generating activities to reduce contamination of skin and clothing.
CDC guidance for TB control in healthcare settings recommends a three-level hierarchy of control measures, with administrative controls at the first and most important level, environmental controls at the second level, and respiratory controls (including respiratory protection, respiratory hygiene, and cough etiquette) at third level. Thus, personal protective equipment (PPE) is still the last line of defense in a TB infection control program and it should be noted that the employer must provide and pay for PPE and train employees in the use and care of the PPE, such as the respirators and coveralls mentioned above.
To read more about a NIOSH Health Hazard Evaluation conducted at an elephant refuge and the specific recommendations made for that facility, visit www.cdc.gov/niosh/hhe/reports/pdfs/2010-0080-3235.pdf.
Stephanie Stevens, MA, is a Health Communication Specialist in the NIOSH Office of the Director.
This is an installment in the NIOSH Workplace Medical Mystery Series. This fictional “mystery” is loosely based on a Health Hazard Evaluation (HHE) conducted by NIOSH and other sources, and any recommendations made herein were for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. HHEs are publicly available at https://www.cdc.gov/niosh/hhe/ but the names of individuals and facilities mentioned in in this series are fictional. For more information on the NIOSH HHE program, visit the website.
Sources:
NIOSH [2015]. Health hazard evaluation report: evaluation of potential employee exposures to Mycobacterium tuberculosis at an elephant refuge. By Niemeier RT, Mead K, de Perio MA, Martin SB, Burr GA. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, NIOSH HHE Report No. 2010-0080-3235.https://www.cdc.gov/niosh/hhe/reports/pdfs/2010-0080-3235.pdf
Murphree R, Warkentin J, Dunn J, Schaffner W, Jones T [2011]. Outbreak of Mycobacterium tuberculosis infection among employees at an elephant refuge. Emerg Infect Dis 17(3):366–371. Retrieved from: www.ncbi.nlm.nih.gov/pmc/articles/PMC3166032/.
Centers for Disease Control and Prevention. (2014). The Flu Season