Todd R. Robeck, DVM; Leslie Dalton, DVM
On March 14, 1994 an 18 yr. old, l 000 kg beluga was presented with a well circumscribed mass on his lower right abdomen. The clinical signs exhibited during the preceding 9 month period were mild and insidious in nature and included sporadic inappetence and behavioral unresponsiveness. Hematologic and serum chemistry changes which were indicative of a chronic infection included slightly elevated total WBC (absolute neutrophilia and monocytosis), gradually decreasing alkaline phosphatase (ALK), serum fe, and MCV.
The mass was sonogramed, and a centrally located 5 cm wide by 2.5 cm deep fluid (blood or pus) filled pocket was identified. A wedge biopsy was performed through the skin, fat and capsule of the abscess to allow drainage. Cultures were obtained from the exudate. The mass was flushed with chlorhexidine (Novasan, Aveco, Co. Inc., Fort Dodge, Iowa 50501, USA) and, pending indentification and sensitivity of the organism(s), the animal was placed on broad spectrum antibiotics. Culture results exhibited a pure growth of a gram positive, filamentous organism; thus, a tentative diagnosis of subcutaneous nocardiosis was made. The animal was placed on trimethoprim/sulfadiazine (Tribrissen, Coopers Animal Health, INC., Kansas City 66103, USA). A positive clinical response was noted and antibiotics were discontinued on March 27, 1994. Microbiological Specialist Inc. (Houston, Texas 77054, USA) identified the organism as Nocardia brasiliensis.
On April 4, 1994, the lesion was again debrided reestablish drainage and cultures taken to reconfirm the organism(s) and its sensitivity to antimicrobials. The culture revealed a mixed infection with both N. brasiliensis and N. asteroides. The animal was placed back on a combination of trimethoprim/sulfadiazine, sulfamethoxazole (Gantanol, Roche Laboratory, Nutley, New Jersey 07110, USA), and folic acid.
By May 7, 1994 the animal had become inappetant and was refusing to cooperate with the training staff. Hematology and chemistries revealed an elevated erythrocyte sedimentation rate (ESR), dramatically decreased serum iron and ALK, and a thrombocytopenia. Based on previous sensitivity, antibiotics were changed to a combination of azithromycin (Zithromax, Pfizer Labs., New York, New York 10017, USA), rifampin (Rimactane, CIBA Pharmaceutical Co., Summit, New Jersey 07901, USA), minocycline (Danbury Pharmacal, INC., Danbury, Connecticut 06810, USA) and itraconazole (Sporanox, Janssen Pharmaceutica, Titusville, New Jersey 08560, USA). The animal was left on folic acid. Clinical and hematologic improvements were noted and antibiotics were stopped on May 25, 1994.
Reoccurrence of inappetence and worsening hematologic and serum chemistry indices occurred on June 29, 1994. The animal was placed on enrofloxacin (Baytril, Miles Inc., Shawnee Mission, Kansas 66201, USA) for 20 days. On August 13, 1994, a second circular lesion measuring 6 cm in diameter and containing a pocket of purulent material was found on the dorsal Caudal area. The lesion was surgically opened, cultured, and flushed with 2% chlorhexidine. The original lesion was examined, debrided and a small fistulus tract discovered which was opened for drainage. The animal was placed back on enrofloxacin based on previous sensitivities and behavioral improvement was noted.
By December 13, 1994 the original lesion was inflamed and had to be reopened and debrided. During the physical exam, a third elevated fluid filled lesion, l 5 cm in diameter, was observed on the right lateral peduncle. Purulent material was aspirated from the new lesion for cultures and sensitivities. It was then surgically opened and debrided. A pure culture of N. brasiliensis was isolated from the exudate.
By January 7, 1995, the animal's condition had again deteriorated. A forth abscess was discovered on the dorsal midline, midway between the dorsal ridge and the blowhole. The abscess was sonogramed, aspirated for organism(s) identification and sensitivity, flushed with 100 ml of physiologic saline solution and infused with 20 ml amikacin (50 mg/ml). Two additional abscesses (for a total of six) were located during the treatment of the forth lesion and were treated in the same manner. Pure cultures of Nocardia .sppwere obtained from the exudate of all the new abscesses. The animal was taken off enrofloxacin and placed on azithromycin PO, amikacin (Amiglyde-V, Fort Dodge Lab., INC., Fort Dodge, Iowa 50501, USA) and ceftriaxone (Rocephin, Roche Laboratory, Nutley, New Jersey 071 10, USA) IM. The three new abscesses were aspirated for cultures and surgically opened one week after the initial treatment. No growth was detected from two of the new lesions and only slight growth from the third. One of the nocardia strains cultured exhibited in-vitro resistant to ceftriaxone, thus it was discontinued on January 30, 1995. Currently, the lesions appear to be healing normally and hematology and chemistry data reveals continued improvement. Treatment is planned for a minimum of 6 months.