Abstract

A female bottlenose dolphin, Tursiops truncatus, was diagnosed in February 2016 at sixteen months old with mucormycosis following routine serum titers of all cetaceans at the facility. Due to the acute and high mortality rate of the disease,¹ treatment was started immediately with posaconazole 890 mg daily (5.0 mg/kg PO BID). Despite continuous treatment ranging from 2.9 mg/kg to 5.0 mg/kg over 27 months, titers remained mostly suspect to positive with few occasions of negative results. Serum titers were obtained via an ELISA validated in 2012 for the detection of Apophysomyces spp. in dolphins (90% sensitivity; 92% specificity).^2,3 The dolphin exhibited no clinical signs of fungal illness or hematological abnormalities at the time of diagnosis or during the remainder of her life.

More aggressive therapy was initiated June 2018 due to the chronicity of and fluctuation in titer levels and the recent successful treatment of aspergillosis in a bottlenose dolphin with high dose posaconazole.⁴ The anti-fungal dose was being slowly increased over several months (max 1600 mg daily; 7.6 mg/kg PO BID) when the dolphin was unexpectedly found deceased in September 2018. Hematology results four days prior to death and immediately postmortem were unremarkable. Fungal elements consistent with Mucor spp. were not observed in the lungs or CNS submitted for histopathology as anticipated; however, were discovered within multifocal granulomas in the larynx and proximal esophagus. The isolation of fungus within granulomas explains the refractory and subclinical nature of the disease, and the animal’s known history of behavioral regurgitation likely contributed to the waxing and waning of titers over time by intermittently traumatically reopening the lesions.

This case demonstrates a less common presentation of mucormycosis which is classically known as an acute and often fatal disease. It also lends as a reminder for assorted diagnostic testing, such as laryngeal and gastric endoscopy, in atypical cases in order to locate the pathogen for possible targeted therapy such as flushing the affected region with antifungals or surgical removal of granulomas when accessible.

Acknowledgements

The authors wish to thank the training staff of Gulf World Marine Park for their superb care of this individual during her life.

* Presenting author

Literature Cited

1.  Staggs L, FI Townsend Jr, E Chesnut, J Boston, R Wells, M Erwin, E Petermann, S Holmes-Douglas. 2012. A retrospective study of mucormycosis cases in the Florida panhandle from 1992-2012. IAAAM 43rd Annual Conference Proceedings, Atlanta, GA.

2.  Barger PC, JC Newton, FI Townsend Jr, LA Staggs, RL Wells, ER Petermann. 2012. A novel diagnostic assay for the rapid detection of mucormycosis caused by Apophysomyces spp. in dolphins. IAAAM 43rd Annual Conference Proceedings, Atlanta, GA.

3.  Barger, PC, JC Newton, LA Staggs, FI Townsend 2019. Indirect enzyme-lined immunosorbent assay for diagnosis of apophysomycosis in dolphins (Tursiops truncatus, Stenella attenuate and Steno bredanensis). In preparation.

4.  Bunskoek PE, S Seyedmousavi, SJM Gans, PBJ van Vierzen, WJG Melchers, et al. 2017. Successful treatment of azole-resistant invasive aspergillosis in a bottlenose dolphin with high-dose posaconazole. Med Mycol Case Rep. 16:16–19.