DAO 121:85-95 (2016)  -  DOI: https://doi.org/10.3354/dao03047

Protozoal-related mortalities in endangered Hawaiian monk seals Neomonachus schauinslandi

Michelle M. Barbieri1,*, Lizabeth Kashinsky2, David S. Rotstein3, Kathleen M. Colegrove4, Katherine H. Haman5,6,7, Spencer L. Magargal7, Amy R. Sweeny7, Angela C. Kaufman2, Michael E. Grigg7, Charles L. Littnan1

1National Oceanic and Atmospheric Administration, Pacific Islands Fisheries Science Center, Protected Species Division, Hawaiian Monk Seal Research Program, Honolulu, HI 96818, USA
2Joint Institute for Marine and Atmospheric Research, University of Hawai’i at Mānoa, 1000 Pope Road, Marine Sciences Building 312, Honolulu, HI 96822 USA
3Marine Mammal Pathology Services, Olney, MD 20832, USA
4Zoological Pathology Program, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, Brookfield, IL 60513, USA
5Health and Genetics Program, Washington Department of Fish and Wildlife, Olympia, WA 98501, USA
6Marine Mammal Research Unit, Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, V6T 1Z4, BC, Canada
7Molecular Parasitology Section, Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, MD 20892, USA
*Corresponding author:

ABSTRACT: Protozoal infections have been widely documented in marine mammals and may cause morbidity and mortality at levels that result in population level effects. The presence and potential impact on the recovery of endangered Hawaiian monk seals Neomonachus schauinslandi by protozoal pathogens was first identified in the carcass of a stranded adult male with disseminated toxoplasmosis and a captive monk seal with hepatitis. We report 7 additional cases and 2 suspect cases of protozoal-related mortality in Hawaiian monk seals between 2001 and 2015, including the first record of vertical transmission in this species. This study establishes case definitions for classification of protozoal infections in Hawaiian monk seals. Histopathology and immunohistochemistry were the primary diagnostic modalities used to define cases, given that these analyses establish a direct link between disease and pathogen presence. Findings were supported by serology and molecular data when available. Toxoplasma gondii was the predominant apicomplexan parasite identified and was associated with 100% of mortalities (n = 8) and 50% of suspect cases (n = 2). Incidental identification of sarcocysts in the skeletal muscle without tissue inflammation occurred in 4 seals, including one co-infected with T. gondii. In 2015, 2 cases of toxoplasmosis were identified ante-mortem and shared similar clinical findings, including hematological abnormalities and histopathology. Protozoal-related mortalities, specifically due to toxoplasmosis, are emerging as a threat to the recovery of this endangered pinniped and other native Hawaiian taxa. By establishing case definitions, this study provides a foundation for measuring the impact of these diseases on Hawaiian monk seals.


KEY WORDS: Protozoa · Mortality · Pathology · Immunohistochemistry · Toxoplasma gondii · Sarcocystis · Pinniped


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Cite this article as: Barbieri MM, Kashinsky L, Rotstein DS, Colegrove KM and others (2016) Protozoal-related mortalities in endangered Hawaiian monk seals Neomonachus schauinslandi. Dis Aquat Org 121:85-95. https://doi.org/10.3354/dao03047

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