Abstract

An adult, wild-caught, 50-kg female pelagic stingray, Dasyatis violacea, presented 30 December 2006 with a cloacal prolapse. The stingray was housed in a 260,000-gallon exhibit tank at the National Aquarium in Baltimore (NAiB) that contained elasmobranchs, including another female pelagic ray, tarpon (Megalops atlanticus), and a green sea turtle (Chelonia mydas). It had been in the collection for 2.5 years and was considered healthy. At the time of presentation she was swimming and behaving normally and had accepted food from the divers that day. An ultrasound and visual examination confirmed that the prolapse was reproductive tissue. The prolapse was reduced, and antibiotics (florfenicol 40 mg/kg IM q5d and clindamycin 5 mg/kg IM SID) were initiated along with pain medication (meloxicam 0.2 mg/kg IM SID and butorphanol 0.4 mg/kg IM SID; the NSAID was changed to carprofen 6 days later at 2 mg/kg PO SID). Hematology and plasma biochemistry results indicated infection and fluid loss and blood culture was negative. Impression smear cytology of the prolapsed tissue showed only a gram-positive coccobacillus; biopsy was not taken.

During the following week, the stingray remained strong and continued to eat. However, the left uterus was thick-walled, and serial ultrasounds revealed increased uterine fluid accumulation and increased echogenicity of the fluid. Enrofloxacin was started at a dose of 10 mg/kg PO SID. On multiple cloacal palpations, the cervix was closed and attempts to pass a catheter or endoscope into the uterus failed. But, on 9 January, the cervix was partially opened and a 12 Fr red rubber catheter was passed into the left uterus. 120 ml of slightly cloudy yellow fluid containing a thin sheet of brown material was removed and soft tissue structures consistent with uterine villi were present. The uterus was partially flushed with 30 ml elasmobranch ringers containing 2 mg/kg amikacin. The soft tissue material was submitted for histology and demonstrated chronic, diffuse cystic degeneration. The fluid was submitted for culture and aerobic culture showed scant growth and anaerobic culture was negative. However, fungal culture had pure growth of an organism on day five but no fungal elements had been seen on the cytology of that same fluid. As a result, fluconazole was started (6 mg/kg loading dose, then 3 mg/kg PO q3d) and clindamycin and enrofloxacin discontinued. Medical management was continued with flushing of the uterus every 5 days with elasmobranch Ringer's solution and itraconazole, florfenicol injections, oral fluconazole, and oral elasmobranch Ringer's solution. Fungal hyphae were seen on cytology of uterine fluid on 18 January.

On 23 January, an ultrasound indicated sloughing of the left uterine wall and continued increase in fluid accumulation; fluid aspirated from the left uterus was dark brown and contained increased fungal hyphae. Clinically the animal had reduced appetite and was weaker and was considered to be in decline. Surgical exploratory was elected due to the deteriorating condition. On 25 January, surgery was performed in an attempt to biopsy the internal organs to check for systemic fungal spread, evaluate organs for predisposing conditions such as neoplasia, and remove the left uterus. Removal of the uterus was not possible so instead, the uterus was flushed and a large-bore tube left in place to keep the cervix dilated. The stingray recovered from surgery but was found dead later that afternoon.

The histopathology confirmed a severe, diffuse, chronic mycotic endometritis. Fungal culture confirmed it as Paecilomyces lilacinus, though no DNA sequencing was done. It grew from the coelomic fluid, liver, uterus, and blood. P. lilacinus can cause severe infections in humans and has been documented in turtles and a crocodile. To the best of our knowledge, infection has not been reported in teleosts or elasmobranchs. Also, while secondary external fungal infections are relatively common in teleosts and elasmobranchs, primary systemic fungal infections are rarely reported. Although initial cytologies and uterine villi biopsies did not show fungal organisms, and secondary infection from antibiotic administration is a possibility, we suspect this was a primary fungal infection due to the severity and chronicity of the lesions. This case thus appears to represent an unusual primary systemic fungal infection with an organism not previously reported in elasmobranchs.

Acknowledgments

The authors would like to thank the NAIB Fishes Department staff, especially Leah Neal, for their help with this case. We would also like to thank Drs. Richard J. Montali and Denise Schultz (pathology fellow), and laboratory staff at Johns Hopkins, Department of Molecular and Comparative Pathobiology for providing the diagnostic pathology studies for this case.