Abstract
In December 2017, a juvenile female ribbon seal was rescued in Morro Bay, CA, well south of the species’ Arctic range. The last extra-limital ribbon seal recorded for the contiguous US west coast was an adult male that stranded in 1962 also at Morro Bay.1 When rescued, the 2017 female was in fair body condition but had extensive alopecia, with the remaining hair easily epilated, and smooth black skin. She had eosinophilia and elevated serum amyloid A.2 Thoracic radiography showed a diffuse interstitial pattern so antibiotic therapy (Florfenicol) was instituted for pneumonia. After a week of uneventful rehabilitation, improved appetite and behavior, she unexpectedly developed hemorrhagic diarrhea, dehydration and hemoconcentration and died despite intensive intervention. Necropsy and histopathology confirmed severe acute segmental necrotizing hemorrhagic enterotyphlocolitis. Clostridium perfringens enterotoxin type A was identified in colonic contents by EIA. Multiple skin sections from the face, head, trunk and flippers showed moderate compact orthokeratotic hyperkeratosis and follicular keratosis with hair follicles in multiple stages of growth, anagen, catagen and telogen. Cocci bacteria were noted within the lumen of some follicles. Small to moderate numbers of eosinophilic intracytoplasmic inclusions (3–10 μm) were noted in the outer root sheath of follicles and sebaceous gland duct epithelium. Multiple hair shafts were fragmented at the follicular os and contained intratracheal hyphae forming scalloped edges into the cuticle and cortex resembling small bites. Compared to the ice seals examined during the 2011–2016 Alaskan Northern Pinniped UME, this was consistent with a “Type-1 case” defined as alopecia without significant dermatitis or systemic illness. In this seal, there was no follicular or adnexal atrophy or dysplasia and no dermal inflammation.3 Many of the UME seals also had the scalloped hair shafts associated with fungal elements and bacteria. Several different fungi and bacteria were identified but there was no causal association between any particular species and the alopecia. Fungi and bacteria from the Morro Bay seal are as yet unidentified.
While the gross appearance (symmetrical non-inflammatory alopecia) of the Morro Bay seal had some features of an endocrinopathy, there was no histologic evidence of atrophy that accompanies these dermatopathies in domestic animals.4 Hormones are only one of the factors that influence directly or indirectly, the hair growth cycle. Others include photoperiod, ambient temperature, nutritional status and general health.5 This ribbon seal was well out of her normal Arctic range and so it is possible that unusual photoperiod and temperatures influenced her molt cycle. Indeed, some dog breeds seasonally develop flank alopecia apparently triggered by changes in circulating melatonin.4 Alternatively, she may have undergone a catastrophic telogen defluxion in which some stimulus prematurely terminated anagen precipitating early onset catagen and telogen and resulting in diffuse non-scarring alopecia.6,7 Defluxion may be precipitated by systemic illness or stress (pregnancy, lactation), or both. In humans, it is generally of short duration as anagen follicles reform in the dermis replacing the lost hair. Whatever the cause, the Morro Bay seal had numerous hair bulbs deep in her dermis that would have resulted in regrowth of her coat.
Acknowledgements
We thank the rescue and animal care staff and volunteers at TMMC, Barbie Halaska and Christine Fontaine (TMMC) for necropsy assistance and sample shipping, and Carlos Rios (TMMC) and Barbara Byrne (UC Davis) for microbiology.
* Presenting author
Literature Cited
1. www.blubberblog.org/files/tag-ribbon-seal.html
2. Sheldon JD, Johnson SP, Hernandez JA, Cray C, Stacy NI. 2017. Acute-phase response in healthy, malnourished, and Otostrongylus-infected juvenile northern elephant seals (Mirounga angustirostris). J Zoo Wildlife Med. 48: 767–775.
3. Black S, Duignan PJ, Akeeagok J, Raverty S. 2016. Marine mammal health in a changing Arctic. In: Cork S, Hall D, Liljebjelke K, eds. One Health Case Studies: Addressing Complex Problems in a Changing World. Sheffield, UK: 5M Publishing Ltd; 160–175.
4. Mauldin EA, Peters-Kennedy J. 2016. Endocrine diseases of skin. In: Maxie MG, ed. Jubb, Kennedy and Palmer’s Pathology of Domestic Animals. 6th ed. St. Louis, MO: Elsevier; 587–590.
5. Mo G, Gili C, Ferrando P. 2000. Do photoperiod and temperature influence the molt cycle of Phoca vitulina in captivity? Mar Mammal Sci. 16:570–577.
6. Yager JA, Wilcock BP. 1994. Atrophic dermatoses. In: Surgical Pathology of the Dog and Cat. Wolfe Publishing, Mosby-Year Book Europe Ltd; 218.
7. Derbes VJ. 1980. Effluvium vs defluxion. Letter to the editor. Arch Derm. 116:21.