Abstract

An approximately 75 kg, 17 year old, female, captive Pantropical spotted dolphin (Stenella attenuata) presented with a honking sound on expiration. Initial diagnostics and treatment included radiographs and doxycycline and itraconazole, respectively. Thoracic radiographs were unremarkable. Respiratory signs progressed to an inspiratory stridor which localized the clinical observation to the extrathoracic respiratory tract. Additional diagnostics included fungal antigen assay (Fungitell, Beacon Diagnostics) for Candida sp. and Aspergillus sp. infection, complete blood count, and clinical chemistry. Fungal assays were negative, the erythrocyte sedimentation rate (ESR) was moderately elevated (7–19 mm/hr), there was a relatively normal white blood cell count (5,400 to 11,200/mcL), while the serum iron fluctuated (34–267 mcg/dl).

We were unable to perform bronchoscopy due to the small size of her airway, dyspnea and distress. Examination of the blowhole revealed a granulomatous plaque within the nasal passages. Cytology was non-diagnostic. We began twice daily dilute Betadine flushes of the nasal passages. After 4 days, the nasal passage plaques were no longer visible but the inspiratory stridor persisted and intermittent bouts of dyspnea occurred. Aminophylline and low dose prednisone were added to the treatment with no clinical improvement. Approximately one month from the observation of clinical signs, she died.

At gross necropsy, two granulomatous "kissing" lesions were identified just caudal to the larynx that extended through the ventral wall of the trachea occluding fifty percent of the lumen. Standard fungal cultures were negative. Histopathological findings included a severe pyogranulomatous fungal pneumonia, pharyngitis, myositis, lymphadenitis and tracheitis. Morphological characteristics of the fungi including irregular branching, non-parallel walls, and occasional septation were consistent with zygomycetes which have been identified as a common cause of clinical illness and death in captive dolphins in northwest Florida. Cutaneous, rhinocerebral, pulmonary, and disseminated zygomycosis have been documented in cetaceans.^1-4

The timing of exposure and infection cannot be clearly stated; however, it is plausible that she was infected earlier the previous year based on the ESR. We have found that severely elevated ESR with relatively normal white blood cell counts have anecdotally correlated with zygomycosis infections in captive dolphins under our care. Perhaps the location of the lesion within the trachea contributed to only moderate elevation of ESR seen with this illness. In August 2009 she presented for anorexia and her ESRs ranged from 30 to 80 (normal range 1–5). She was treated with posaconazole (Noxafil) for possible zygomycosis for 1 month and the ESR decreased to 3. Two additional anorexic episodes occurred in October and December 2009, with ESR levels ranging from 21 to 55 that resolved each time with antibiotic treatment alone.

Pulmonary zygomycosis has a very poor prognosis. In humans with fungal tracheitis, there is a 55% mortality rate with medical treatment alone. Successful treatment occurred in a patient treated surgically with primary reanastomosis and a patient that was medically managed with liposomal amphotericin B and hyperbaric oxygen; however, a permanent tracheostomy was needed due to severe fibrosis.^5,6 Severe stenosis secondary to fibrosis was also seen in an Atlantic bottlenose dolphin with chronic fungal tracheitis.³

References

1.  Dalton LM, McBain JF. Mucormycosis in three cetaceans. IAAAM 24th Annual Conference Proceedings, Chicago, Illinois; 1993; p. 50.

2.  Dougherty MM, Bossart GD. The use of a new antifungal, terbinafine (Lamisil) as a possible prophylactic treatment for Apophysomyces elegans in cetaceans. IAAAM 32nd Annual Conference Proceedings, Tampa, Florida. 2001; pp. 171–172.

3.  Kinsel MJ, Briggs MB. Chronic fungal tracheitis with stenosis in an Atlantic bottlenose dolphin (Tursiops truncatus). IAAAM 36th Annual Conference Proceedings, Seward, Alaska; 2005; pp. 41–43.

4.  Townsend F, Williams A, Staggs L. The successful treatment of systemic zygomycosis in a bottlenose dolphin (Tursiops truncatus) calf. IAAAM 37th Annual Conference Proceedings, Nassau, Bahamas; 2006; 113–114.

5.  Kwan VY, Louie S, Milkowski D. Tracheal zygomycosis presenting as stridor and acute upper airway obstruction, successfully treated with medical therapy and hyperbaric oxygen. Chest 2004; 126(4): 941S–942S.

6.  Schwartz JR, Nagle MG, Elkins RC, Mohr JA. Mucormycosis of the trachea: an unusual cause of acute upper airway obstruction. Chest 1982; 81: 653–654.