An adult Eurasian Eagle Owl (Bubo bubo) rescued from drowning was unable to fly. After euthanasia, necropsy and histopathologic examination showed granulomatous inflammation and intracellular acid-fast stain-positive rod-shaped bacteria in the skin, lung, liver, and spleen, which were identified by using molecular analysis as Mycobacterium abscessus.
Nontuberculous mycobacteria (NTM) are present in soil and water (Gcebe and Hlokwe 2017). In humans, NTM are known to cause multiple organ infections including pulmonary infection and lymphadenitis (Koh et al. 2013; Johnson and Odell 2014; Lee et al. 2015). In South Africa and Europe, several species of NTM have been isolated from lesions similar to tuberculous lesions in wild animals (García-Jiménez et al. 2015; Gcebe and Hlokwe 2017).
An adult Eurasian Eagle Owl (Bubo bubo) was rescued from drowning after it was caught in a net in the Republic of Korea. Initial examination revealed 10% dehydration and low body temperature (<34 C). The wet feathers of the bird were dried, and it was stabilized for a day. On day 2, the bird exhibited inappropriate flight ability in terms of flight distance, height, and posture. Physical examination revealed crackle sounds on inhalation, plus superficial corneal ulcers in both eyes. Radiographic examination, complete blood count, and clinical chemistry revealed no abnormal findings. The bird received intramuscular administration of empirical systemic amoxicillin/clavulanate (Amocla®, Kuhnil Pharm, Seoul, Republic of Korea) and meloxicam (Metacam®, Boehringer Ingelheim, Ingelheim am Phein, Germany) for the possibility of pulmonary infection, and nebulization with a combination of gentamicin (Gentamicin injection®, Shin Poong Pharm, Seoul, Republic of Korea), aminophylline (Aminophylline injection®, Dai Han Pharm, Seoul, Republic of Korea), and acetylcystein (Mucomyst®, Boryung Pharm, Seoul, Republic of Korea) was performed daily. A topical antibiotic and a cell regeneration promoter (Solcoseryl, Solcorin®, Hanrim Pharm, Yongin, Republic of Korea) were instilled for corneal ulcers, and subcutaneous fluid was administered to improve the systemic condition. After 1 wk, dermatitis was observed in the perineum and left carpal joint. Additionally, the left carpal joint showed swelling and bruising. The range of motion of the carpal joint of the left wing was 130–140°. Fine needle aspiration cytology of the left carpal joint revealed granulomatous inflammation in which macrophages were the main inflammatory cells, and a mixed pattern of various bacteria presumed to be caused by lesion contamination. While the bacterial culture of the aspirates was conducted, pentoxifylline (Pentoxin®, Hutecs Pharm, Hwaseong, Republic of Korea) was given in addition to the same antibiotic and nonsteroidal anti-inflammatory drugs. The following day, the skin over the joint was observed to be dry, necrotic, and malodorous; feathers of this area had been shed (Fig. 1a). Subsequently, the range of motion worsened (110°). The next day, most of the original lesions had turned necrotic and developed a foul odor, and similar lesions were identified near the left ulna. Euthanasia was carried out because of the poor prognosis for survival in the wild.
Necropsy revealed ulceration and necrosis of the skin in the left carpal joint area (Fig. 1b). A solid mass of approximately 1.5 cm diameter was observed within the skin lesion. Unexpectedly, necropsy revealed fibro-purulent exudates filling the pericardial space and attached to the epicardium (Fig. 1c). Small numbers of multifocal white nodules (less than 1 mm diameter) and fibro-purulent debris were observed in the lung tissue (Fig. 1d). A few multifocal white nodules (less than 1 mm) were observed in the liver and spleen (Fig. 1e, f). Histopathologically, the skin showed acanthosis and caseous necrosis in the epidermis. In some areas, a pseudomembrane composed of mononuclear inflammatory cells and fibrinous exudate was formed and covered the epidermis. Numerous degenerated inflammatory cells were accumulated in the epidermis. Acid-fast bacteria were detected in the pseudomembrane (Fig. 2a). The solid mass found in the carpal joint showed caseous necrotic changes, and mononuclear inflammatory cells were infiltrated into the mass. Variable sizes of canal were observed inside the mass. The margins of the canals were composed of necrotic cellular debris; acid-fast bacteria were detected throughout the mass, especially at the canal margins (Fig. 2b). Granulomas of various sizes were observed in the heart, lung, liver, and spleen, and were composed of a central caseous necrotic area and peripheral multinucleated giant cells (Fig. 2c, d). Using Ziehl-Neelsen stain, acid-fast bacilli were detected throughout the granulomas. The multinucleated giant cells had an atypical shape, and vacuolar structures with various sizes were observed inside. Acid-fast positive reactions were observed both in multinucleated giant cells and in peripheral mononuclear inflammatory cells. On the outside of the multinucleated giant cell zone, mononuclear inflammatory cells formed a border and encapsulated the granuloma (Fig. 2c, d). Within some of giant cells, aggregated acid-fast bacteria were observed (Fig. 2e). Acid-fast rod-shaped bacilli also were observed in lung parenchyma and inside granulomas (Supplementary Material Fig. S1a, b).
We performed molecular analyses for bacterial identification. Genomic DNA was extracted from the skin, heart, lung, liver, and spleen using a QIAamp® DNA Mini kit (Qiagen, Hilden, Germany). The PCR amplification was performed with primers 16SRNAF and 16SRNAR for the mycobacterial 16S rRNA gene, as described (Huard et al. 2003). Similarly, the rpoB gene was amplified using the primers MycoF and MycoR, as described (Adékambi et al. 2003). Compared to the sequences in the GenBank database, the 16S rRNA gene sequence was identified as Mycobacterium sp. (GenBank accession no. AP018436). Because the sequence of the rpoB gene was 100% identical to that of M. abscessus (GenBank accession no. JF346872), and considering all the relevant information, the patient was finally diagnosed with systemic NTM infection (Fig. 3).
Mycobacterium abscessus is a part of a group of environmental mycobacteria related to those that cause tuberculosis and leprosy (Franco-Paredes et al. 2018). In wild animals, M. abscessus infection has been reported in lions (Panthera leo), hyenas (Crocuta crocuta), and leopards (Panthera pardus) (Gcebe and Hlokwe 2017) but not in birds. In humans, M. abscessus is included in a group of rapidly growing mycobacteria that are responsible for infection of the skin and internal organs (Lee et al. 2015). A human skin infection has been described with M. chelonae/abscessus infection at the site of a bite by a pet cockatoo, indicating the possibility that the bird might have been a transmitter of the mycobacteria (Larson et al. 2008). Once the infection is established, M. abscessus forms granulomas, which help the bacteria to resist the immune system (Johansen et al. 2020). In our case, the owl was initially suspected to have a simple infection limited to the skin, but necropsy revealed widespread infection of the internal organs, suggesting that the infection might have become established before the rescue. Mycobacterial pathogenic factors, and the fact that the bird was caught in a fishing net for quite some time and restricted in a small cage during hospitalization, might have caused immunosuppression. This could have triggered the rapid collateral spread of mycobacterial infection to the skin.
This publication was supported by the National Institute of Wildlife Disease Control and Prevention as “Specialized Graduate School Support Project for Wildlife Disease Specialists.”
Supplementary material for this article is online at http://dx.doi.org/10.7589/JWD-D-21-00156.