Abstract
In cetaceans the gram-positive bacteria Erysipelothrix rhusiopathiae causes two widely recognized forms of clinical disease, a chronic cutaneous and an acute septicemic form. The clinical course of the latter is often peracute in onset and duration, resulting in the death within 24 hours of any discernable clinical signs of illness in a cetacean.
In September 2002, a five-year-old, 169 kg. male Atlantic bottlenose dolphin was reported by training staff as exhibiting a sudden onset of depressed behavior and poor appetite. Initial diagnostics revealed a severe leukopenia (247/mm3) and thrombocytopenia (39,000/mm3). Serum chemistries were essentially normal. Immediate therapy was initiated, including ceftriaxone (20 mg/kg IM), amikacin (10 mg/kg IM), dexamethasone sodium phosphate (0.2 mg/kg IM), cimetidine (3 mg/kg IM), and oral fluid therapy (2 liters). Blood culture later revealed pure growth of Erysipelothrix rhusiopathiae.
Over the next week, hematology showed leukocytosis, severe thrombocytopenia, and a nonregenerative anemia. A progressive uremia (BUN of 123 mg/dl, creatinine of 10.6 mg/dl) and hyperphosphatemia (a high of 15.2 mg/dl) developed. Intensive management of the dolphin involved administration of enrofloxacin, amoxicillin/clavulanic acid, itraconazole, furosemide (later switched to spironolactone for potassium sparing properties), dexamethasone, intravenous and subcutaneous fluid therapy (up to 12 liters per day). A light fish gruel was orogastrically tubed every four hours for nutritional support. Hyponatremia (low of 135 mg/dl) and hypochloremia (low of 100 mg/dl) necessitated the substitution of normal saline for water in the gruel formulation, as well as the crystalloid of choice for parenteral fluid supplementation. Hypocalcemia was also noted during this period. Calcium glubionate (30 mls. PO, Rugby, Duluth, GA 30097) was administered for calcium supplementation and aluminum hydroxide gel (30 mls. PO, Rugby, Duluth, GA 30097), for phosphorus binding in the gastrointestinal tract.
Despite this therapy, the dolphin's condition deteriorated. He displayed intermittent periods of dyspnea and showed occasional bloody, frothy discharge from the blowhole. Pleural and abdominal effusions were confirmed with ultrasound and pulmonary edema was suspected. Fluid volumes were reduced to one liter six times daily and furosemide was reinstituted due to its superior effectiveness in maintaining diuresis. Oxygen supplementation was also provided on an hourly basis to improve gaseous exchange. Treating the pleural effusion was complicated by managing the dolphin's worsening renal failure. Beside alterations in fluid therapy, antibiotic and antifungal choices and doses were changed to carbenicillin (31 mg/kg PO TID), lomefloxacin (4.4 mg/kg PO SID), and terbinafine (1.0 mg/kg PO BID). Nutritional support was supplemented by the addition of calorically dense fish oils to the gruel, as well as the use of a high quality protein, low phosphorus product (Nepro®, Ross Laboratories, Columbus, OH 43215) often utilized in human dialysis patients.
After approximately two and a half weeks, the dolphin's blood parameters improved. Platelet numbers began to recover, followed by the return of kidney enzymes toward normal levels. Hyperphosphatemia and hypocalcemia gradually resolved. The white blood cell count steadily declined to reach the high end of normal range, and fibrinogen levels decreased, though never to pre-illness levels. After five weeks of continuous therapy, the dolphin was underweight, but clinically normal. Diego is now actively participating in the training program at Discovery Cove.
This case highlights several key aspects of the successful management of a peracute Erysipelothrix rhusiopathiae septicemia in dolphins. Prompt, aggressive therapy is of paramount importance. Institution of fluid therapy is a fundamental component of the treatment regimen, yet must be monitored closely so as to avoid over hydration and pulmonary complications. A recognition of the need to amend or scale dosages of medications dependent on renal excretion is vital as well. Patience, persistence, and the clinician's ability to be flexible in formulation of the therapeutic plan, sometimes on a daily or even hourly basis, is essential. Lastly, and perhaps most crucial to attaining a positive outcome in a case of this type, is a dedicated and caring staff to implement that therapeutic plan, as was done for this animal.
Acknowledgements
The authors would like to recognize the Discovery Cove Training Department, SeaWorld veterinary technicians and Veterinary Services Laboratory staff, Stewart J. Clark, John Kerivan, Dr. Stacy Randall, Dr. Jim McBain, and Dr. Jorge Ramirez for their assistance in this case.