Abstract

Captive cetaceans including beluga whales (Delphinapterus leucas) have considerable morbidity and mortality from lower respiratory tract infections.^1-6 It was reported that the exhaled blowhole sample culture was unreliable to identify the pathogenic microorganisms from lower respiratory tract in bottlenose dolphin (Tursiops truncatus).^4,7 In cetaceans, bronchoscopy with bronchoalveolar lavage (BAL) is becoming an essential diagnosis to identify the pathogenic microorganism from lower respiratory tract.^4,6 However, little is reported about the bronchial tree system, standardized methods for bronchoscopy, and BAL evaluation of cetaceans, including beluga whale.^2,4-6

In this study, 37 bronchoscopies using sterilized flexible endoscopes, 9.3 mm outer diameter (OD), 3000 mm length (VQ-9303C, Olympus, Tokyo, Japan) and 9.4 mm OD, 2000 mm length (EN-450T5/W, Fujifilm, Tokyo, Japan) were examined for six beluga whales (body length: 357–452 cm, male: 3, female: 3). The scopes were selected from a previously reported that BAL was proceeded with 9.8-mm scope.⁸ Two of six beluga whales were under antifungal treatment. Videos of bronchoscopy were taken three times from each five of the six beluga whales to analyze the bronchus lengths and bifurcated bronchi from left principal, right principal, and right tracheal bronchus (LPB, RPB, and RTB, respectively). Exhaled blowhole samples (n=28) were taken within 10 days before/after the day of BAL collection. Each 28 BALs and exhaled blowhole samples in six beluga whales were compared by the fungal culture with Sabouraud’s medium. The 50 ml saline were put and withdrawn at each terminal of LPB, RPB, and RTB (LPBt, RPBt, and RTBt) to get BAL.

The distances from blowhole to LPBt, RPBt, and RTBt were 110–155 cm, 113–155 cm and 80–110 cm, respectively. These distances were corresponded to the body length of the beluga whales. The 9.3-mm diameter scope identified 10–12, 10–12, 6–9 bifurcated bronchi in LPB, RPB, and RTB, respectively. The first to fifth bifurcation from LPB (LB1–5), and the first bifurcation from RPB (RB1) were observed from stable sites. Other bronchi were sometimes absent or excessive as well as displaced bifurcation.^2,9

BAL fungal cultures were negative in 35.7% (10/28), positive in 64.3% (18/28). The exhaled blowhole sample cultures were negative while BAL cultures were negative. The cultured fungi from BAL were Candida sp., Aspergillus sp., Zygomycetes, and unidentified fungus. In these 18 cases where fungal cultures were positive in BAL, the exhaled blowhole sample cultures, 66.7% (12/18) was negative, 27.8% (5/18) was positive with different species, and 5.6% (1/18) was positive with the same species compared to the BAL samples.

In conclusion, this study had four major findings in beluga whale bronchoscopy. First, bronchial tree system had individuality. Second, BALs from LPBt, RPBt, and RTBt were collected well with both endoscopes. Third, the exhaled blowhole sample was unreliable, whereas BAL was reliable to identify pathogenic fungus from lower respiratory tract. Fourthly, the risk of contamination was low to transport fungus from upper to lower respiratory tract through the bronchoscopy. These findings could be useful solutions for the early diagnosis, pathogenic fungal identification, health maintenance, and effective treatment for the beluga whale. It is expected that these findings could be applied for accurate lower respiratory infection diagnosis to other cetaceans.

Acknowledgments

The authors wish to thank Port of Nagoya Public Aquarium for the contribution to this study.

*Presenting author

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