A 21-month-old 21.4-kg (47.1-lb) spayed female Border Collie was examined because of progressive right forelimb lameness of 2 weeks' duration. Results of a physical examination were unremarkable, and rectal temperature was within reference limits. The dog was treated with carprofen (4.4 mg/kg [2 mg/lb], PO, q 12 h) for 7 days, but the lameness became more severe over the next 4 weeks, to the point that the dog would not bear weight on the limb. Pitting subcutaneous edema developed in the right axillary region and extended to the mid portion of the right forelimb, right axilla, ventral aspect of the neck, and left axilla. The skin overlying the right axilla and forelimb contained several well-defined areas of deep-red discoloration overlying 1- to 3-cm-diameter firm nodules within the subcutis and subjacent soft tissues. Results of a CBC and serum biochemical profile were unremarkable, and radiography of the right forelimb revealed diffuse soft tissue swelling but no skeletal abnormalities. The dog was treated with ciprofloxacin (15 mg/kg [6.8 mg/lb], PO, q 12 h) and carprofen (4.4 mg/kg, PO, q 12 h) for 10 days with no improvement.
Over the following 2 weeks, subcutaneous edema and soft tissue swelling worsened to extend along the entire right forelimb to the level of the carpus, right axilla, ventral aspect of the neck, and left axilla. Signs of pain were evident during palpation of all edematous areas, and palpation of the nodular areas resulted in signs of intense pain. At this time, results of thoracic radiography and a CBC were normal, but rectal temperature was high (39.3°C [102.7°F]). The dog was treated with dexamethasone sodium phosphate (1.5 mg/kg [0.68 mg/lb], IV, once), amoxicillin-clavulanic acid (18 mg/ kg [8.2 mg/lb], PO, q 12 h for 7 days), and tramadol (2 mg/kg [0.9 mg/lb], PO, q 8 to 12 hours as needed for pain).
Two days later, a biopsy specimen was obtained from a nodule adjacent to the triceps brachii muscle, and radiographs of the entire right shoulder region were obtained. Soft tissue swelling had decreased slightly by this time. No skeletal abnormalities were seen on radiographs of the right shoulder region, but linear radiolucent lines could be seen within the soft tissues cranial to the shoulder joint. Histologic examination of the biopsy specimen revealed fibroplasia and chronic panniculitis.
Swelling and signs of pain continued to progress over the next 10 days. Skin overlying the right axilla, ventral aspect of the chest, and right forelimb developed several well-defined areas of deep-red discoloration (ecchymotic hemorrhages), and several 1- to 3-cm-diameter firm nodules could be identified within the subcutis and subjacent soft tissues. Suspecting that the initial biopsy had not yielded diagnostic tissues, the veterinarian conducted a second biopsy. An incision into one of the discolored areas in the right axilla revealed an approximately 2-cm-diameter cystic cavity containing coiled aggregates of many (> 100) intact and fragmented white worms ranging from 10 to 30 mm in length and 2 to 4 mm in width. The cavity was traced and found to extend from the right axilla deep to the right pectoral muscle medially and cranially to the left thoracic inlet. The cavity also extended subcutaneously laterally and distally to the point of the right elbow. Flushing the cavity with saline (0.9% NaCl) solution (approx 5 L) produced multiple live worms. A Penrose drain was placed in the pocket and sutured to the skin, and the incision was closed.
Initial anthelmintic treatment included praziquantel (20 mg/kg [9.1 mg/lb], PO, q 24 h for 5 days) and fenbendazole (50 mg/kg [22.7 mg/lb], PO, q 24 h for 3 days). The worms were tentatively identified as tetrathyridia of Mesocestoides spp. Therefore, treatment with fenbendazole was continued at a higher dosage (100 mg/kg [45.5 mg/lb], PO, q 12 h for 28 days). Over the next few days, flushing of the cavity with sterile saline solution yielded additional live parasites. Signs of pain and swelling of the right forelimb and axilla subsided for 1 week, but the tissues remained firm and cool. The dog continued to be profoundly lame, and a large fluid-filled bulla formed in the skin overlying the sternum. Before the bulla was ruptured, worms could be seen floating freely in serosanguinous fluid within the bulla. Thoracic radiography was repeated to determine whether there was any thoracic involvement, but results were normal.
Samples of the worms were submitted to the Diagnostic Parasitology Service of the Department of Pathobiology at the Auburn University College of Veterinary Medicine for identification. The worms were identified as larval cestodes, plerocercoids, or spargana of a pseudophyllidean tapeworm, most likely Spirometra spp. Seven days after surgery, the Penrose drain was left in place because live worms and copious amounts of serosanguinous fluid were still recovered from the drain openings.
Treatment with fenbendazole was continued at the same dosage (100 mg/kg, PO, q 12 h), and cefpodoxime proxetil (2.5 mg/kg [1.1 mg/lb], PO, q 24 h for 10 days) and metronidazole (24 mg/kg [10.9 mg/lb], PO, q 12 h for 7 days) were added to the treatment regimen. The dog was referred to the University of Florida Veterinary Teaching Hospital for further diagnostic testing and treatment.
At the Veterinary Teaching Hospital, thoracic and abdominal ultrasonography revealed mild pleural and peritoneal effusions. Treatment with fenbendazole (100 mg/kg, PO, q 12 h) was continued, and praziquantel (50 mg/kg, SC, divided among 6 sites) was given once a week for 3 weeks. Moderate soft tissue swelling and signs of pain were noticed at injection sites for several days after praziquantel was administered. The Penrose drain was removed 2 weeks after surgery, but moderate amounts of serosanguinous fluid continued to drain from the wound.
Swelling of the right forelimb and signs of pain subsided somewhat, and for 3 weeks, no plerocercoids (spargana) were observed in fluid draining from the wound. However, several new bullae developed over the ventral aspect of the thorax, right side of the neck, and right axillary region, and serous fluid developed in the thorax. Treatment with fenbendazole (100 mg/kg, PO, q 12 h) and praziquantel (50 mg/kg, SC, once a week) was continued.
After 28 days, treatment with fenbendazole was discontinued. At this time, all wounds were healing and signs of pain were less severe, although the dog continued to have signs of moderate to severe pain and swelling at praziquantel injection sites. One week after the third praziquantel injection, the dog developed dyspnea and fever (40.3°C [104.5°F]), and new lesions erupted on the ventral aspect of the chest and in the right axilla. The dog had a poor appetite and had lost 1.5 kg (3.3 lb) over the past 2 weeks. Radiography revealed an effusion within the right pleural cavity, and thoracocentesis yielded approximately 500 mL of cloudy serosanguinous fluid. A CBC and serum biochemical profile revealed mild anemia, mild monocytosis, and moderate hypoalbuminemia, but WBC count was within reference limits. Treatment with enrofloxacin (3.5 mg/kg [1.6 mg/lb], PO, q 12 h) was begun, and a sample of the pleural fluid was submitted for bacterial culture. Pseudomonas aeruginosa susceptible to enrofloxacin was obtained.
The dog was treated with praziquantel (30 mg/kg [13.6 mg/lb], PO, q 24 h) for 8 days. Within 2 weeks, the dog developed a pendulous abdomen, and abdominocentesis yielded 2.3 L of serosanguinous fluid. Cytologic examination of the fluid revealed scattered segmented neutrophils, but no bacteria were seen. The dog's appetite continued to be poor, and the dog had lost an additional 1.5 kg during this 2-week period. Nitazoxanide (500 mg, PO, q 12 h) was administered for 2 weeks, in addition to enrofloxacin and carprofen, but the dog's anorexia became worse, and the dog began vomiting. Metoclopramide (0.3 mg/kg [0.14 mg/lb], SC, then 0.3 mg/kg, PO, q 12 h as needed for vomiting) and famotidine (0.5 mg/kg [0.23 mg/lb], IM, then 0.5 mg/kg, PO, q 12 h) were administered.
The dog's overall body condition and attitude deteriorated dramatically, although body weight was still 18.5 kg (40.7 lb) because of fluid accumulations in the thoracic and abdominal cavities. The owners elected to euthanatize the dog, and the body was submitted to the Anatomic Pathology Service of the Department of Pathobiology at the Auburn University College of Veterinary Medicine for necropsy.
At necropsy, the subcutis and intermuscular fascia of the right forelimb, right axilla, ventral thoracic midline, and ventral cervical region contained many inflammatory tissue cysts filled with nodules of entangled intact and degenerate white larval cestodes (spargana) surrounded by red, cloudy, thick fluid (Figure 1). There was severe atelectasis of the right lung, and the right pleural cavity contained about 150 mL of thick, cloudy, tan fluid with 2 larval cestodes and scattered white, friable fragments. There was partial atelectasis of the left lung, and the left pleural cavity contained about 100 mL of cloudy tan fluid with several free-floating larval cestodes. Microscopic examination of smears of the pleural fluid stained with Wright-Giemsa stain revealed many bacteria both extracellularly and within neutrophils. The peritoneal cavity contained about 250 mL of red, cloudy fluid, and microscopic examination of the fluid revealed many bacteria and segmented neutrophils. There were many fibrous adhesions between the omentum and serosal surfaces of the small intestine, spleen, and stomach. At least 2 larval cestodes were present in the peritoneal fluid. Cestodes were frozen immediately for DNA analysis and fixed in glutaraldehyde and 10% formalin.
Histologically, parasitic cysts were characterized by chronic pyogranulomatous myositis associated with draining tracts that contained plerocercoid larvae (Figure 2). The pleura and lungs were characterized by pyogranulomatous pleuritis and severe pulmonary atelectasis. There was severe pyogranulomatous peritonitis in conjunction with fibrosis of the serosa and omentum. The pleural and peritoneal cavities contained scattered plerocercoid larvae and abundant bacteria. The larvae lacked a digestive tract and demonstrated frequent but shallow invaginations of the tegument but no strobiliation. Parenchymal cavities were lined by tegument and were often filled with a granular intensely eosinophilic substance. Microtriches projected from the surface of the tegument. In some areas, subtegumentary cells formed palisades beneath the densely eosinophilic tegumentary syncytium. The body was comprised of evenly distributed, loose parenchyma with calcareous corpuscles, muscle fibers, and excretory ducts (Figure 3). No genitalia were present. Muscle fibers were loosely arranged in a discontinuous row that was oriented parallel to the tegument. In some areas, muscle fibers were arranged haphazardly through the body. Scolices were not present; however, deep invaginations suggestive of hold-fast bothria could be identified. Larvae were surrounded by hemorrhage, mixed inflammation (macrophages, lymphocytes, and neutrophils), and deeply eosinophilic aggregates of granular substance and calcareous corpuscles occasionally forming spheric concretions within the tissues. Some sections of larval cestodes had an amphophilic tegument with no discernible invaginations (dead larvae). The walls of cavities containing dead larvae had extensive fibrosis and fibroplasia. Other sections had a brightly eosinophilic tegument with prominent invaginations (viable larvae). There was regional myofiber loss, with replacement by fibrosis. The right axillary lymph node was severely atrophied and edematous, and subcapsular sinuses contained multiple aggregates of eosinophilic amorphous substance similar to that surrounding the larvae in tissue cysts.
Nucleic acid was extracted from intact frozen spargana with a robotic extractora used in accordance with the manufacturer's directions, and a PCR assay incorporating eucestode primers 84 and 90 was used to amplify a fragment of the 18S rDNA, as described.1 Amplicons were sequenced at the Oklahoma State University core facility with a capillary sequencer, and sequences were compared with reported sequences for Spirometra erinacei (D64072), Diphyllobothrium latum (AM778553), Mesocestoides corti (AF286984), and Taenia solium (DQ157224). Amplicon sequences (EU392209) most closely resembled (99.4% identical) previously reported sequences for pseudophyllidean cestodes.
Maxwell 16, Promega Corp, Madison, Wis.
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