Assessing Brucella ceti Infections in Oregon and Washington Dolphins that Stranded with Histopathological Lesions Resembling Neurobrucellosis, 2006-2014

Assessing Brucella ceti Infections in Oregon and Washington Dolphins that Stranded with Histopathological Lesions Resembling Neurobrucellosis, 2006-2014 Tabitha George This thesis documents the presence of Brucella ceti in the Pacific white-sided dolphin (Lagenorhynchus obliquidens), striped dolphins (Stenella coeruleoalba), and shortbeaked common dolphins (Delphinus delphis) that stranded with histopathological lesions resembling neurobrucellosis in Oregon and Washington between 2006 and 2014. These Brucella strandings occurred in very specific years (2006, 2012, and 2014) and seasons (winter and fall), which may have been driven by an increase in the number of overall strandings, or an environmental influence, altering their susceptibility to the disease. Further studies on the linkages between climate and disease will provide a better understanding on factors that might drive the emergence of seasonal or interannual variations seen within Brucella stranded individuals. Out of fifteen individuals that had histopathological lesions resembling neurobrucellosis upon histology, fourteen were sent for further Brucella tests and ten (71%) came back positive. The positive individuals in this study were confirmed by culture and serology. However, there were a high number of false negative PCR and IHC results, making me believe that 71% is an underestimate of the actual percentage of Brucella positive individuals. Demographically speaking, the striped dolphin (n=6) was the most common species to be infected with Brucella ceti, followed by the short-beaked common dolphin (n=3). This study is also the first, to my knowledge, to document Brucella in a Pacific white-sided dolphin. The observed predilections at this time include male striped dolphins, subadult individuals of all species, and short-beaked common dolphins that strand in Washington. These observed predilections are based off of a small sample size and may be subject to change if further tests are performed on prior individuals that tested negative for Brucella and from future strandings. Ultimately, individuals with histopathological lesions suspicious of neurobrucellosis most often came back positive for Brucella ceti on further tests.