Abstract

Short-beaked common dolphin (Delphinus delphis) strandings occur frequently on Cape Cod, MA.^1,2 Brucella spp. have been isolated from many cetacean species and were implicated in a recent bottlenose dolphin unusual mortality event in the mid-Atlantic region.^3-5 In order to better understand the prevalence and clinical significance of Brucella spp. exposure and infections in stranded common dolphins on Cape Cod, a retrospective and prospective study was conducted. Between 2011 and 2021, IFAW sampled 265 stranded D. delphis for Brucella spp. through serological (ELISA), qPCR, and/or culture assays. Of tested cases, 34% were seropositive for Brucella antibodies (56/163), with annual seropositive prevalence ranging from 17–48%. Ten of 136 cases were positive for Brucella spp. on qPCR (7%), three of which were confirmed Brucella ceti and genotyped to either ST26 or ST23. Positive PCR results were most frequently identified in spleen (n=4/49, 8%), reproductive tract (n=2/25, 8%), and blowhole swab (n=3/58, 5%). Seven of 21 cases were positive for Brucella spp. on tissue culture (33%), three of which were also positive on PCR. Cause of death was determined in 40 cases, two of which were attributed to brucellosis. Observed diseases in these two cases included: atlanto-occipital synovitis, meningitis, hepatic necrosis, myocarditis, pericardial effusion, and orchitis. There were several other cases (n=8) where brucellosis was suspected on histopathology, but lesions were not sufficient to cause stranding or death. Results from this study indicate that brucellosis plays a minor role in common dolphin strandings on Cape Cod, MA but support its endemicity in this cohort.

*Presenting author

Literature Cited

1.  Sharp SM, Knoll JS, Moore MJ, Moore KM, Harry CT, Hoppe JM, Niemeyer ME, Robinson I, Rose KS, Sharp WB, Rotstein D. Hematological, biochemical, and morphological parameters as prognostic indicators for stranded common dolphins (Delphinus delphis) from Cape Cod, MA, USA. Marine Mammal Science. 2014;30:864–887.

2.  Sharp SM, Harry CT, Hoppe JM, Moore KM, Niemeyer ME, Robinson I, Rose KS, Sharp WB, Landry S, Richardson J, Moore MJ. A comparison of postrelease survival parameters between single and mass stranded delphinids from Cape Cod, Massachusetts, U.S.A. Marine Mammal Science. 2016;32:161–180.

3.  Guzmán-Verri C, Gonzalez-Barrientos R, Hernandez-Mora G, Morales JA, Baquero-Calvo E, Chaves-Olarte E, Moreno E. Brucella ceti and brucellosis in cetaceans. Frontiers in Cellular and Infection Microbiology. 2012;2:3.

4.  Colegrove KM, Fauquier D, Terio K, Quance C, Tiller R, Wu Q, Venn-Watson S, Robbe-Austerman, Rotstein D, Rowles T. Brucella infections in North American cetaceans: pathology, genetics, and unanswered epidemiologic questions. In: IAAAM 47th Annual Conference Proceedings. Virginia Beach, VA; 2016.

5.  Curtiss JB, Colegrove KM, Dianis A, Rotstein D, Fauquier D, Rowles T, Niemeyer M, Kinsel MJ, Terio KA. Pathology of Brucella ceti infection in cetaceans according to sequence type. In: IAAAM 50th Annual Conference Proceedings. Durban, South Africa; 2019.