The 2010–2015 Northern Gulf of Mexico Cetacean Unusual Mortality Event: An Update on Diagnostic Test Results and Pathologic Findings
IAAAM 2015
Kathleen Colegrove1*; Stephanie Venn-Watson2; Jenny Litz3; Michael Kinsel1; Karen Terio1; Jeremiah Saliki4; Spencer Fire5; Ruth Ewing3; Erin Fougeres6; Ruth Carmichael7; Connie Chevis8; Wendy Hatchett8; Jonathan Pitchford8; Mandy Tumlin9; Cara Field10; Suzanne Smith10; Deborah Fauquier11; Gretchen Lovewell12; Heidi Whitehead13; David Rotstein14; Wayne McFee15; Teresa Rowles11
1Zoological Pathology Program, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Maywood, IL, USA; 2National Marine Mammal Foundation, San Diego, CA, USA; 3National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, FL, USA; 4Athens Veterinary Diagnostic Laboratory, College of Veterinary Medicine, University of Georgia, Athens, GA, USA; 5NOAA National Ocean Service, Marine Biotoxins Program, Charleston, SC, USA; 6National Marine Fisheries Service, Southeast Regional Office, St. Petersburg, FL, USA; 7Dauphin Island Sea Lab and University of South Alabama, Dauphin Island, AL, USA; 8Institute for Marine Mammal Studies, Gulfport, MS, USA; 9Louisiana Department of Wildlife and Fisheries, Baton Rouge, LA, USA; 10Audubon Aquarium of the Americas, New Orleans, LA, USA; 11National Marine Fisheries Service, Office of Protected Resources, Silver Spring, MD, USA; 12Mote Marine Laboratory, Sarasota, FL, USA; 13Texas Marine Mammal Stranding Network, Galveston, TX, USA; 14Marine Mammal Pathology Services, Olney, MD, USA; 15National Centers for Coastal Ocean Science, National Ocean Service, Charleston, SC, USA
Abstract
An unusual mortality event (UME), unprecedented in magnitude and duration for bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico remains open. The Deepwater Horizon (DWH) oil spill began on April 20, 2010 and exposure to petroleum products is proposed as a contributor to moderate to severe lung disease, impaired stress response, and poor health in live dolphins examined in Barataria Bay, Louisiana in 2011.1 Evidence to date does not support biotoxins or morbillivirus as primary factors in this UME. Histologic lesions were evaluated in non-perinate and perinate (less than 115 cm length) dolphins stranding in Louisiana, Mississippi, and Alabama from June 2010 to December 2013 and compared to reference dolphins stranding outside the UME area. Compared to references, non-perinate UME dolphins were more likely to have primary bacterial pneumonia (26% vs. 2%), severe pneumonia (16% vs. 2%) and thin adrenal cortices (33% vs. 7%). Bacterial pneumonia was most common in 2010 and less prevalent in 2011–2013. The proportion of dolphins with a thin adrenal gland cortex decreased in 2013. A higher proportion of perinatal UME dolphins compared to references died in utero, had fetal distress and had pneumonia not associated with lungworm infection. Some pneumonias were due to Brucella sp. infections, and multiple Brucella strains were identified during the event. While the investigation is ongoing, the DWH spill may be a contributing factor to the increased susceptibility to bacterial pneumonia, adrenal cortical atrophy, and fetal distress and in utero pneumonia noted in the dolphins.
Acknowledgements
The authors would like acknowledge the Southeast US Marine Mammal Stranding Network, particularly the staffs of Louisiana Department of Wildlife and Fisheries, Audubon Aquarium of the Americas, Institute for Marine Mammal Studies, Dauphin Island Sea Lab, Emerald Coast Wildlife Refuge, and Gulf World Marine Park for their continued hard work during this event. We also thank the NMFS SEFSC, SERO and OPR staff, the Incident Command staff, those who traveled to the Gulf to assist with carcass recovery and examinations including the perinate team, as well as, the Working Group on Marine Mammal Unusual Mortality Events and the UME investigative team. This work was part of the Deepwater Horizon Natural Resources Damage Assessment (NRDA) being conducted cooperatively among NOAA, other Federal and State Trustees, and BP. We thank Cynthia Smith, Lori Schwacke, and Sylvain DeGuise for valuable insight on data interpretation.
* Presenting author
Literature Cited
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