Human Exposures to Marine Brucella Isolated from a Harbor Porpoise — Maine, 2012

On February 10, 2012, the Maine Center for Disease Control and Prevention (Maine CDC) was notified of a positive Brucella culture from a harbor porpoise (Phocoena phocoena) found on the coast of southern Maine. Maine CDC, in consultation with CDC, initiated an investigation of potential occupational exposures of staff members at university A and at diagnostic laboratories known to have handled samples from the porpoise. This report describes the results of that investigation. In humans, brucellosis can cause fever, sweats, headaches, back pains, physical weakness, and sometimes severe infections of the brain, bone, heart, liver, or spleen. Because staff members at university A did not use respiratory protection while handling the porpoise or its specimens, the four exposed staff members were advised to begin immediately a 3-week regimen of rifampicin and doxycycline for antimicrobial prophylaxis, conduct daily fever checks, be monitored for symptoms of acute febrile illness weekly, and have their serum tested for Brucella antibodies immediately and at regular intervals for 24 weeks after the last known exposure. As of June 26, none of the four persons had seroconverted or become ill. The potential for human infection and illness as well as the intensity, duration, and expense of the follow-up recommended for Brucella exposure highlights the need for facilities to develop standard protocols for preventing exposures during the handling of marine mammals, particularly during aerosol-generating procedures.

On January 28, 2012, a porpoise carcass was recovered by a rescue team affiliated with a marine mammal facility at university A. On January 29, a necropsy of the porpoise was performed in a small room at university A by a faculty member, two students, and a community volunteer. All wore gloves and gowns but worked without respiratory protection. The necropsy included removal of necrotic tissue from the uterine horn and the use of an electric saw with an oscillating blade to cut the skull to evaluate the brain. The same four persons who performed the necropsy also cleaned the room after the procedure. The necropsy room did not have a separate air supply, but the air was exhausted directly outdoors; therefore, persons in rooms adjacent to the necropsy room were considered to have minimal to no risk for exposure to Brucella. A swab of the uterine horn tissue was sent to laboratory A, which specializes in veterinary diagnostics. The sample was sent as an unknown diagnostic sample to laboratory A and successfully cultured. The cultured organism had morphologic and microscopic characteristics of Brucella, and the isolate was forwarded to laboratory B for identification. Once a high suspicion that the isolate might be a Brucella species was noted, standard biosafety level 3 (BSL-3) laboratory precautions were taken at both laboratories, including use of a biosafety cabinet for specimen manipulation. On February 15, samples from laboratory B were received at CDC for confirmatory testing. The isolate was identified by multilocus sequence typing as sequence type 23, a known sequence type associated with harbor porpoises. DNA tests for further differentiating the marine species (Brucella pinnepedialis and Brucella ceti) are limited. Based on the fact that the isolate originated from a cetacean, it likely was B. ceti.

On February 10, 2012, Maine CDC was notified by laboratory B of the positive Brucella culture. Maine CDC initiated an investigation to determine the potential for occupational exposure among persons who had handled the porpoise or the specimens. Because of the potential for aerosolization of Brucella organisms during the necropsy and the lack of respiratory precautions taken, the four persons who performed the necropsy were assessed to be at high risk for Brucella exposure. Laboratories A and B reported using proper procedures in handling unknown samples, and no potential laboratory exposures were identified. Maine CDC consulted with CDC, and recommendations for the four exposed persons included 1) an immediate 3-week course of antimicrobial prophylaxis with rifampicin and doxycycline, 2) Brucella serologic monitoring performed by CDC laboratories, 3) self-administered daily fever checks, and 4) weekly monitoring for symptoms of acute febrile illness for 24 weeks (1).

Reported by

Stephen Sears, MD, Maine Center for Disease Control and Prevention, Maine Dept of Health and Human Svcs; Kate Colby, MPH, Univ of Southern Maine and Maine Center for Disease Control and Prevention. Rebekah Tiller, MPH, Marta Guerra, DVM, Div of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases; John Gibbins, DVM, Div of Surveillance, Hazard Evaluations, and Field Studies, National Institute for Occupational Safety and Health; Mark Lehman, DVM, EIS Officer, CDC. Corresponding contributor: Marta Guerra, [email protected], 404-639-3951.

Editorial Note

Brucellosis is a zoonotic infection uncommon in the United States but endemic in many parts of the world, where it most commonly affects cattle, swine, goats, and sheep. During 2000–2009, an average of 113 human cases was reported to CDC annually (2). Human cases in the United States commonly are associated with consuming unpasteurized milk, hunting feral swine, and inadvertent exposure among laboratory workers who handle Brucella species. Brucellosis can have an incubation period ranging from days to months. Brucellosis can cause fever, sweats, headache, back pain, physical weakness, and sometimes severe infections of the brain, bone, heart, liver, or spleen. Moreover, human cases of brucellosis have been associated with marine mammals. Four human cases of brucellosis caused by marine mammal Brucella species have been reported since 2001. Three cases were attributed to environmental exposures (3,4); two of the patients reported symptoms consistent with neurobrucellosis, and the third was diagnosed with spinal osteomyelitis. The single laboratory-acquired infection caused a mild form of brucellosis (5).

Antimicrobial postexposure prophylaxis recommendations are based on risk assessment for the exposed person. A 3-week course of doxycycline and rifampicin is recommended for persons at high risk (1). For persons at high risk who cannot tolerate doxycycline, a 3-week course of trimethoprim-sulfamethoxazole and rifampicin is recommended. Persons who are at low risk for exposure should discuss the need for antimicrobial therapy with their health-care provider, and antimicrobial therapy should be based on individual health factors. Symptom surveillance includes regular (e.g., weekly) symptom watch and self-administered daily fever checks for 24 weeks after last known exposure for persons at low and high risk. Serologic testing is recommended for persons at high risk immediately and at regular intervals for 24 weeks after the last known exposure (1).

An increase in strandings and deaths of marine mammals along U.S. coastlines during 2010–2012 has increased the likelihood of human/animal interactions, which increase the risk for exposure to Brucella species and other pathogenic organisms (6). Persons who handle stranded marine mammals or carcasses should be made aware of any potential health risks associated with these activities and use appropriate personal protective equipment (7).

The potential for human infection and illness, as well as the intensity, duration, and expense of the follow-up recommended for Brucella exposures, highlights the need for standard protocols for preventing exposures during the handling of marine mammals, particularly during aerosol-generating procedures. When developing protocols for the rescue, care, treatment of marine mammals, or the performance of laboratory procedures or necropsies on these animals, precautions should be focused widely to protect workers from a broad range of infectious organisms.

Given the extensive involvement of students and volunteers in the rescue and handling of stranded marine mammals, facilities should provide the same level of training and protection for this population as they do for employees. If this is not feasible for administrative reasons, facilities should restrict the participation of nonemployees in procedures deemed to be of higher risk based on the facility's risk assessment, such as aerosol-generating procedures or cleaning of facilities and equipment after necropsy. The recently published Guidelines for Safe Work Practices in Human and Animal Medical Diagnostic Laboratories (8) provides a comprehensive approach to safe work practices in various human and animal diagnostic laboratory settings, including animal necropsy facilities. The guidelines emphasize prevention of occupational injury and illness in laboratory settings through the use of engineering tools, administrative policies, and personal protective equipment.

Acknowledgments

Patricia Bosse, MPH, Maine Center for Disease Control and Prevention, Maine Dept of Health and Human Svcs. Meredith Morrow, MSPH, Div of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, CDC.

References

1. CDC. Laboratory-acquired brucellosis—Indiana and Minnesota, 2006. MMWR 2008;57:39–42.
2. CDC. Summary of notifiable diseases—United States, 2009. MMWR 2009;58:85–8.
3. Sohn AH, Probert WS, Glaser CA, et al. Human neurobrucellosis with intracerebral granuloma caused by a marine mammal Brucella spp. Emerg Infect Dis 2003;9:485–8.
4. McDonald WL, Jamaludin R, Mackereth G, et al. Characterization of a Brucella sp. strain as a marine-mammal type despite isolation from a patient with spinal osteomyelitis in New Zealand. J Clin Microbiol 2006;44:4363–70.
5. Brew SD, Perrett LL, Stack JA, Macmillan AP, Staunton NJ. Human exposure to Brucella recovered from a sea mammal. Vet Rec 1999;144:483.
6. National Marine Fisheries Service. 2010–2012 cetacean unusual mortality event in northern Gulf of Mexico. Silver Spring, MD: National Oceanic and Atmospheric Administration, Office of Protected Resources, National Marine Fisheries Service; 2012. Available at http://www.nmfs.noaa.gov/pr/health/mmume/cetacean_gulfofmexico2010.htm. Accessed June 25, 2012.
7. Scheftel JM, Elchos BL, Cherry B, et al. Compendium of veterinary standard precautions for zoonotic disease prevention in veterinary personnel: National Association of State Public Health Veterinarians 2010. J Am Vet Med Assoc 2010;237:1403–22.
8. CDC. Guidelines for safe work practices in human and animal medical diagnostic laboratories. MMWR 2012;61(Suppl):1–101.