Macroscopic and Histopathologic Findings From a Mass Stranding of Rough-Toothed Dolphins (Steno bredanensis) in 2005 on Marathon Key, Florida, USA

Abstract

On March 2, 2005 ~70 rough-toothed dolphins ( Steno bredanensis ) mass stranded along mud flats and associated canals on the Atlantic Ocean side of Marathon Key, Florida. Forty-six were necropsied and placed into two groups for analysis: Group-1 animals ( N = 34; 65%) that died prior to medical intervention and rehabilitative efforts and Group-2 animals ( N = 12; 35%) that died in rehabilitation. Thirty-four animals were females (18 adults, 5 juvenile/subadult, 7 calves, and 4 of undetermined age) and 12 were males (6 adults, 4 juvenile/subadults, 1 calf, and 1 of undetermined age). Body condition overall was fair to good in Group-1 and fair to poor in Group-2. Lesions were observed in multiple body systems. Greater than 90% of animals in both groups had respiratory lesions. Verminous sinusitis and bronchopneumonia were 2–3 times more prevalent in Group-2. Capture/exertional rhabdomyolysis was observed in Group-2 (42%). Vacuolar hepatopathies were observed in both groups including hepatic lipidosis (Group-1) and mixed etiologies (Group-2). Pancreatic and gastrointestinal tract pathologies were prevalent in Group-2 animals 56 and 75%, respectively, and included gastritis, gastric ulceration, enterocolitis, pancreatic atrophy, and pancreatitis related to physiologic stress. Group-2 more frequently had evidence of hemorrhagic diathesis present which included increased extramedullary hematopoiesis in various organs, increased hemosiderosis, and hemorrhage and hemorrhagic drainage in various organs. Central nervous system disease, primarily edema, and mild inflammation were equally prevalent. Renal proteinuria, tubular necrosis, and pigmentary deposition were observed in Group-2. Dental attrition was observed in ~40% of the groups. Gammaherpesviral-associated pharyngeal plaques were observed in 46 and 54% of Group-1 and 2 animals, respectively. Other lesions observed were mild and incidental with a frequency rate <20%. The findings from this Steno stranding provide a unique window into baseline individual and population clinical conditions and additional perspective into potential clinical sequelae of rehabilitation efforts.

Systematic Determination of Herpesvirus in Free-Ranging Cetaceans Stranded in the Western Mediterranean: Tissue Tropism and Associated Lesions

“…Similar plaque-like mucosal proliferations around the larynx have been associated with GHV in Rough-Toothed Dolphins (Steno bredanensis) [80]. Other lesions affecting the mucosa of the upper digestive tract, particularly in oral mucosa and the tongue, have also been associated with HV infection in cetaceans [9,16,22,80]. Moreover, erosive and ulcerative lesions in the distal region of the esophagus associated with GHV infection have been described in sea lions [29].…”

“…With regard to the digestive system, the most striking lesions were the papillomatoidshaped structures in the esophagus, around the larynx, which histologically corresponded to focally expansive irregular acanthosis (Figure 8). Similar plaque-like mucosal proliferations around the larynx have been associated with GHV in Rough-Toothed Dolphins (Steno bredanensis) [80]. Other lesions affecting the mucosa of the upper digestive tract, particularly in oral mucosa and the tongue, have also been associated with HV infection in cetaceans [9,16,22,80].…”

Worldwide phylogeography of rough‐toothed dolphins (Steno bredanensis) provides evidence for subspecies delimitation

“…This is essential for seemingly pelagic species like the rough‐toothed dolphin, which are challenging to study, yet also inhabit coastal areas where anthropogenic threats are greater. For the rough‐toothed dolphin these threats are particularly prevalent on the coastlines of the western North and South Atlantic Oceans where mass strandings, pollution, and fishery interactions occur (Donato et al, 2019; Ewing et al, 2020; Lailson‐Brito et al, 2012; Lemos et al, 2013; Lodi & Maricato, 2020; Meirelles & Barros, 2007; Monteiro‐Neto et al, 2000). Off the coast of Brazil in particular, rough‐toothed dolphins have one of the highest rates of fishery bycatch of any small cetacean (Donato et al, 2019).…”

“…As a worldwide species, rough‐toothed dolphins are listed by the IUCN as Least Concern (Kiszka et al, 2019). Despite this listing, mass stranding events off the United States Eastern Seaboard and coasts of Hawaiʻi (Ewing et al, 2020; Mazzuca et al, 1999; Nitta & Henderson, 1993), Senegal (Cadenat, 1949), and elsewhere, as well as fishery interactions around the Hawaiian, Society, and Samoan archipelagos and off the coast of Brazil (Baird, 2016; Di Beneditto et al, 2001; Monteiro‐Neto et al, 2000; Nitta & Henderson, 1993) and elsewhere continue to be documented, potentially resulting in higher impacts to these populations than is currently known. Furthermore, off the coast of Brazil where rough‐toothed dolphins inhabit neritic waters, additional anthropogenic impacts including plastic ingestion and organochlorine compound accumulation are a concern (da Silva et al, 2015; Lailson‐Brito et al, 2012; Lemos et al, 2013).…”

Highly divergent herpesviruses in threatened river dolphins from Brazil

“…Alphaherpesvirus infections in cetaceans have been associated with cutaneous disease and sometimes fatal localized or systemic infections such as fatal vasculitis and encephalitis 42 – 45 , but also with subclinical infections 45 , 46 . In cetaceans, gammaherpesvirus have been detected in asymptomatic infections 46 , and associated with cutaneous 47 , 48 , but especially with mucosal lesions (mainly genital, oral and oropharyngeal) 42 , 49 – 51 , which might be able to impact reproduction in affected populations 52 .…”