Abstract
Stranded cetaceans commonly present with pneumonia and other respiratory tract lesions of varying degrees of severity.1,2,3 The goal of this study was to describe respiratory pathology among odontocetes that stranded along the southeastern coast of Florida during 2013–2020. Gross and microscopic pathological data were reviewed from the archives of Florida Atlantic University’s Harbor Branch Oceanographic Institute Marine Mammal Stranding and Population Assessment Program to identify cases with respiratory pathology. Of 32 animals with complete gross and histopathology data, 25 cases (78%) were identified to have respiratory lesions, including 10 Atlantic bottlenose dolphins (Tursiops truncatus), 6 pygmy sperm whales (Kogia breviceps), 3 melon-headed whales (Peponocephala electra), 2 Atlantic spotted dolphins (Stenella attenuata), 1 dwarf sperm whale (Kogia sima), 1 Gervais’ beaked whale (Mesoplodon europaeus), 1 Blainville’s beaked whale (Mesoplodon densirostris), and 1 sperm whale (Physeter macrocephalus). These 25 cases consisted of 3 calves, 2 juveniles, 4 subadults, and 16 adults. Pulmonary edema was the most common respiratory abnormality (n=20), followed by pneumonia (n=14) including alveolar (n=7), interstitial (n=7), and bronchopneumonia (n=2), pulmonary hemorrhage (n=11), granulomatous inflammation (n=8), congestion (n=6), emphysema (n=3), pleural fibrosis (adhesions) (n=2), and interstitial fibroplasia (n=2). Six cases had verminous pneumonia, characterized by infestation with nematodes (presumptive Halocercus spp., n=4) and trematodes (n=2), and two cases had mixed bacterial and fungal pneumonia. Diffuse pulmonary pneumoconiosis, presumably resulting from inhalation of anthropogenic particles, was observed in one bottlenose dolphin and one pygmy sperm whale. Pulmonary lymphadenopathy was observed in 10 cases, including eight cases with pneumonia, one with pleural fibrosis and emphysema, and one with pulmonary congestion and fibroplasia. Frozen, archived respiratory tissue samples (lung, pulmonary and tracheal lymph nodes, blowhole, and tracheal swabs) from these cases were submitted to the University of Georgia Veterinary Diagnostic and Investigational Laboratory for PCR testing for morbillivirus, influenza, parainfluenza, coronavirus, and Mycoplasma spp. Lung tissue from a bottlenose dolphin that stranded in 2013 tested positive for Cetacean morbillivirus (100% sequence identity), Mycoplasma spp., and parainfluenza. Lung tissue from a bottlenose dolphin that stranded in 2018 with severe, verminous, and mixed fungal and bacterial pneumonia tested positive for Mycoplasma spp., with 98% sequence identity to M. gallinaceum. Lung tissue from a Gervais’ beaked whale that stranded in 2019 with severe pyogranulomatous and verminous bronchopneumonia, pulmonary edema, and congestion tested positive for Mycoplasma spp., with 95% sequence identity to Mycoplasma spp. strain 3166. All samples tested negative for influenza and coronavirus. Verminous pneumonia in free-ranging cetaceans may be associated with immune suppression from other factors such as contaminant exposure, while pulmonary congestion and edema are often associated with drowning, shock, and cardiopulmonary arrest.1,4,5,6 Mycoplasma spp. has been isolated from the lungs of cetaceans that stranded with pneumonia off the coasts of Italy and Scotland, but to the authors’ knowledge this is the first report of its isolation in lung samples from cetaceans that stranded in North America.7,8
Acknowledgements
Many thanks to Florida Atlantic University’s Harbor Branch Oceanographic Institute’s marine mammal stranding response team, especially Steve Burton and Adam Schaefer. Thanks to Dr. Susan Sanchez for assistance with bacterial isolate sequence interpretation. This work was funded by grants from the Florida Protect Wild Dolphins and Protect Florida Whales specialty license plate grants, administered by the Harbor Branch Oceanographic Institute Foundation.
*Presenting author
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