Brucella Infections in North American Cetaceans: Pathology, Genetics, and Unanswered Epidemiologic Questions
Kathleen Colegrove1*; Deborah Fauquier2; Karen Terio1; Christine Quance3; Rebekah Tiller4; Qingzhong Wu5; Stephanie Venn-Watson6; Suelee Robbe-Austerman3; David Rotstein7; Teresa Rowles2
1Zoological Pathology Program, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Maywood, IL, USA; 2National Marine Fisheries Service, Office of Protected Resources, Silver Spring, MD, USA; 3National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, United States Department of Agriculture, Ames, IA, USA; 4Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA; 5Hollings Marine Laboratory, National Ocean Service, National Oceanic Atmospheric Administration, Charleston, SC, USA; 6National Marine Mammal Foundation, San Diego, CA, USA; 7Marine Mammal Pathology Services, Olney, MD, USA
Two species of Brucella have been identified in marine mammals (B. ceti and B. pinnipedialis). Due to increasing reports of Brucella positive tissues and brucellosis in cetaceans, including animals dying during recent unusual mortality events (UMEs), a multi-institutional investigation was initiated in 2010 to better understand the role of Brucella sp. in free-ranging cetacean heath. Specific goals included describing the pathologic lesions associated with cetacean brucellosis and describing and comparing the strains of Brucella present. Screening for infections was completed using real-time polymerase chain reaction (PCR) with primers directed at either the 16s or IS711 genes and/or culture. Brucella strains were characterized by Omp gene sequencing, multi-locus sequence typing (MLST) and whole genome sequencing. Histopathology was completed on positive cases when possible. Since 2010, over 180 cetaceans of six species from 17 states have tested positive for Brucella sp. via PCR and/or culture. Positive cases have been documented from all coastal regions, though regional differences in disease prevalence may exist. In adult animals the most common positive samples were spinal cord, cerebrospinal fluid, brain, and joint fluid, whereas, lung was most commonly positive in perinates. The most common lesions in non-perinates were lymphocytic meningitis or meningoencephalitis and arthritis. Endometritis, orchitis, and pneumonia were occasionally documented. Perinate lesions included in utero pneumonia and fetal distress. Brucella infections have been diagnosed in 39 dolphins dying during the morbillivirus associated 2013–2015 Mid-Atlantic UME. Genetic analysis determined that multiple strains of Brucella caused disease in cetaceans and most strains amplified from perinates (ST27) were genetically distinct from non-perinate strains. These results raise the possibility that there are strain differences in susceptibility and/or disease pathogenesis. More research is needed to determine potential modes of transmission and epidemiologic factors involved in disease dynamics in cetacean populations.
* Presenting author