Central Park Aquatic Health, Buffalo, NY, USA and Aquarium of Niagara, Niagara Falls, NY, USA
The patient was a 71kg female Harbor seal (Phoca vitulina) 26 years of age living with three other female harbor seals in an outdoor exhibit using fresh or brackish water. She developed a 2 cm cutaneous swelling noted on January 22 of 2006. It continued to grow in circumference with a raised outer margin and a slightly depressed center giving the appearance of a crater. On January 30 cutaneous punch biopsy, cytology and culture were done. Cytology showed neutrophils but no bacteria or parasites were seen. Skin scrapings did not show any parasites. She was started on enrofloxacin 8mg/kg twice daily. Culture produced a coagulase negative Staphylococcus. The histologic diagnosis was "diffuse moderate subacute perivascular and perifollicular dermatitis with pigmentary incontinence." No etiologic agent could be identified.
The lesion continued to enlarge to about 8cm in diameter and the surface of the skin became covered with a yellow, adherent exudate which seemed to be expressed when area palpated. The area was treated with warm compresses, betadine scrub or spray and Gentamicin ointment once or twice daily. On February 17 two areas of drainage were noted. Since the sensitivity results for the Staphylococcus showed Cephalexin to be effective she was switched to 1000mg three times daily. With drainage I expected the lesion to resolve. She was moved to a smaller pool with NaCl and S.G. of 1.022.
However, the lesion continued to progress, developing a pebbly raised appearance. After cleaning the adherent material from the skin round raised lesions could be seen on the skin surface. They appeared to be small granulomas ranging from 3mm to 6 mm in diameter. The tops of these raised lesions were fragile and easily abraded. Due to lack of response to treatment the antibiotic therapy was stopped to allow repeat cultures. On March 20, 2006 aspirates for culture and cytology were taken and cultures taken from the skin surface. The aspirate cultures were done by prepping the skin with betadine and alcohol, aspirating with a 22 gauge, 24 mm needle and immediately expelling the aspirated material onto blood agar plates. When growth occurred the colonies were sub-cultured onto blood agar and submitted for id and antibiotic sensitivities were done in my lab to get quicker results. The original culture plates were kept under refrigeration. Again a Staphylococcus was obtained from the surface and in smaller numbers from the aspirate. A gram-negative rod was also cultured from the surface. Sensitivities showed enrofloxacin or cephalexin should have been effective. Cytology showed numerous neutrophils but also numerous large cells with poorly defined cytoplasmic borders, large open nuclei, all with at least one nucleoli and some with several nucleoli.
With continued growth and enlargement of the lesion I reexamined the cytology slides and did an acid-fast stain which revealed acid fast rods some of which appeared to be intracytoplasmic.
Retrieving the saved culture plates and doing an acid-fast stain showed an acid-fast rod. The original plates were submitted to a local human hospital with expertise in acid-fast organisms. This lab cultured two strains of coagulase negative Staphylococcus, a beta hemolytic strep and Alcaligines sp. They also cultured Mycobacterium fortuitum. An antibiotic susceptibility test was done for the Mycobacterium using antibiotic discs and measuring zones of inhibition. The lab made no promises of clinical relevancy of this test but the results were: Amikacin 27mm, Azithromycin 32mm, Cefotoxin no zone, Ciprofloxacin 17 mm, Clarithromycin 50mm, Doxycycline no zone, Imipenem 24 mm, and TMP/SXT no zone. Clarithromycin is available for oral administration in 500mg and Enrofloxacin is closely related to Ciprofloxacin so they were selected for treatment. She was started on Enrofloxacin 600mg twice daily and started on a small dose of Clarithromycin planning to increase to 500 mg three times daily. 250mg twice daily markedly reduced her appetite so for the first 4 days she received 125mg twice daily, and the enrofloxacin was decreased to 600mg once daily. She tolerated that so the Clarithromycin was increased to 250mg twice daily. On the 10th day of treatment she was given 500mg in the morning, 250mg at noon and 500mg at night. This treatment was continued until September 17, approximately 5 months.
She had a WBC of 26,000/ul at the time of the first biopsy but other lab values were normal and subsequent lab work was also with normal limits. The last sample done was July 17 after 3 months of treatment.
With this treatment the lesion stopped growing. Exudate was no longer produced and the surface appeared to be healing and the raised bumps were covered with normal epithelium. During restraint for blood work pressure on the lesion loosened the epithelium from the dermis with hemorrhage and development of a hematoma. The abnormal skin became necrotic and she was sedated for debridment. Histology of the excised tissue and underlying granulation tissue revealed "dermal pyogranulomatious dermatitis and cellulitis." No acid fast organisms were seen but the previous cytology slides were submitted for more expert exam and intracytoplasmic gram-negative rods were seen. I think the antibiotic treatment had eliminated organisms before this tissue was collected. Debriding the lesion revealed a nice bed of granulation tissue and the area was expected to granulate and heal by second intention.
This proceeded nicely and the lesion was 1/2 the original size when a raised red area appeared near the anterior border. This grew rapidly to 2 cm in diameter. The raised portion was excised for histology and culture. Culture did not produce any acid fast organisms. The histologic diagnosis was "spindle cell sarcoma with extensive inflammation and hemorrhage." The mass grew back quickly so an excision with margins greater than the diameter of the original lesion was performed and at this writing 9 months after that excision there is no recurrence.
Exam of records and photos shows an injection of West Nile Virus vaccine made 7 months before the lesion was first seen at what appears to the be the exact site of the lesion. This may represent the inciting cause for this problem. The area was prepped with alcohol and the injection made with 22 gauge 1 inch needle with aspiration before injection.
I wish to thank the Department of Laboratory Medicine, Erie County Medical Center, Buffalo, NY and Dr. Drury Reavill of Zoo/Exotic Pathology Service And the Staff of Aquarium of Niagara for help with this case.