Abstract
“Lumpy jaw” or necrobacillosis is a term used to describe the infectious inflammation of the mandibular bone in mammals.1-3,6,7 It is a chronic bacterial infection most often involving Nocardia asteroides, Actinomyces bovis, Fusobacterium necrophorum, and Nocardia macropodidarum, but additional bacterial organisms may be involved.1-3,6,7 Although it is most often described as occurring in the mandible, cases have been observed in the maxilla.7 Metastatic abscesses have been observed in numerous cases1,3,7 and must be taken into consideration when initially evaluating a case of necrobacillosis.
“Lumpy jaw” occurs in numerous species of mammals, including marsupials, domestic and exotic ruminants and exotic porcines.1-3,6,7 It is thought to arise from a break in the integrity of the periodontal ligament. Reasons for this are unclear, although hypovitaminosis A, coarse stemmed plant material, and dental disease, combined with overcrowding, stress, and poor husbandry practices probably predispose to this condition.3-7
Treatment involves long-term administration of antibiotics, curettage of the affected bone with local administration of iodine solutions, nitrofurazone, or sulfanilamide, and affected tooth extraction. Many cases are refractory to treatment, and permanent extensive bone remodeling can occur.3,7
A 6-year-old, intact female Bennett’s wallaby, weighing 14 kg, was presented for a 1-day history of having a small amount of swelling over the ventral aspect of the body of the left mandible. During the day, the wallaby was maintained with six other conspecifics in a fenced, natural outdoor exhibit measuring 15x10 m. During the evening, the animals were housed in an outdoor 25x20-m fenced, gravel and sand enclosure with access to multiple wooden stalls with concrete floors. The diet consisted of an alfalfa-based pelleted ration (Mazuri ADF, PMI Feeds, St. Louis, MO, USA), alfalfa hay, fresh daily browse in the form of bamboo (Phyllostachys sp.), and willow (Salix sp.), and moderate amounts of fresh fruits and vegetables as enrichment items.
The animal was manually restrained, and a physical examination revealed a firm mass involving the bone of the mandible. Treatment was initiated with 350x103 IU of penicillin G benzathine combined with penicillin G procaine (Pen BP-48, Pfizer Animal Health, Lee’s Summit, MO, USA) IM via blowdart every 48 hours for 21 days. No improvement was noted, and the wallaby was immobilized with 140 mg of ketamine hydrochloride (Ketaset, Fort Dodge Laboratories, Overland Park, KS, USA), and 25 mg xylazine hydrochloride (Rompun, Bayer Corp., Agriculture Division, Animal Health, Shawnee Mission, KS, USA) IM via blowdart. The wallaby was maintained on a heated surgery table, and IV buffered fluids (Lactated Ringer’s Solution, Abbott Laboratories, North Chicago, IL, USA) were administered at 20 ml/kg/hour. Radiographs at that time revealed osteolysis and osteomyelitis of the left mandibular body. Oral examination revealed mild dental calculus, but no apparent gingival disease. The skin over the lesion was surgically prepped and incised. The bone was surgically curetted and flushed with 1% iodine solution. Characteristic “sulfur granules”7 were observed, and staining of the necrotic material revealed gram-positive filamentous rods and rosettes of presumed sulfur granules. Aerobic and anaerobic culture failed to demonstrate any growth. Antibiotic treatment was continued for an additional 45 days.
Minimal improvement was noted upon survey radiographs, and the wallaby was immobilized as before for reevaluation, additional bone curettage, and packing the resultant opening with iodine-soaked sterile gelatin (Gelfoam, Upjohn Co., Kalamazoo, MI, USA). Aerobic and anaerobic culture at that time revealed scant growth of Actinomyces sp. Histopathology of a bone biopsy revealed an osteomyelitis with filamentous, branching bacteria, presumably Actinomyces or Nocardia sp. Over the course of the following 3 months, continued antibiotic treatment and two additional surgical curettages were performed as before. After the last immobilization, daily flushing of the resultant opening with iodine solution was performed. Minimal improvement was noted after an additional 10 days of treatment, and antibiotic therapy was changed to 100-mg clindamycin (Antirobe Aquadrops, The Upjohn Co., Kalamazoo, MI, USA) PO, BID for 90 days, at which time radiographs and physical palpation under anesthesia revealed progression of the osteomyelitis.
Hemimandibulectomy was proposed as a final alternative due to the chronicity and unresponsiveness of the lesion. The wallaby was anesthetized as before, intubated via a Cole technique with a 4.0-mm cuffed endotracheal tube (Baxter Healthcare Corp., Pharmaseal Division, Valencia, CA, USA), and maintained on 2.5% isoflurane (AErrane, Anaquest, Madison, WI, USA). The wallaby was placed in dorsal recumbency, the area over the ventral mandible was clipped, surgically prepped, and a standard hemimandibulectomy8 was performed by making an 8-cm incision that extended from the mandibular symphysis, along the left mandibular body past the angular process, then curved dorsally parallel to the mandibular ramus. Incision of the platysma muscle with the skin allowed elevation of the masseter and digastricus muscles from the affected bone with a Freer periosteal elevator, taking care to avoid the facial artery and vein. Hemorrhage was controlled with monopolar electrocautery and suction. The mandibular symphysis was separated with an oscillating saw, followed by subperiosteal dissection along the more normal architecture of the mandibular ramus. The temporomandibular joint was sharply incised, and the left hemimandible was manipulated to allow elevation of the remainder of the masseter from the coronoid process. The surgical site was copiously lavaged with sterile saline prior to closure of the fascia of the masseter and digastricus muscles with 3-0 polydioxanone (PDS II, Ethicon, Inc., Somerville, NJ, USA) in a simple continuous pattern. The subcutaneous tissue was closed similarly, followed by intradermal skin closure with 4-0 polyglactin (Vicryl, Ethicon, Inc.). One injection of penicillin (Pen BP) and 5 mg butorphanol tartrate (Torbutrol, Fort Dodge Laboratories) were administered IM postoperatively. The bone specimen was cultured aerobically and anaerobically, then fixed in 10% neutral buffered formalin, embedded in paraffin, and sectioned at 5 µm. The remaining dental arcades were filed to lessen the chance of buccal or gingival trauma. The wallaby recovered uneventfully and was placed in a holding stall at the Animal Health Center of the zoo. Butorphanol was continued for 10 days, and antibiotics were changed to trimethoprim/sulfadiazine (Tribrissen 48%, Mortar and Pestle Pharmacy, Des Moines, IA, USA) at 30 mg/kg SID via blowdart.
Cultures demonstrated scant growth of Actinomyces sp. Histopathologic interpretation of the bone revealed necrosis and osteomyelitis with occasional non-acid-fast, filamentous bacteria, presumably Actinomyces sp.
The postoperative appearance was aesthetically pleasing. Minimal differences in physical appearance were observed; the wallaby was able to maintain the tongue in a normal position, although frequent extension/protrusion was observed for several days after surgery. A moderate median shift in the right mandible occurred secondary to the loss of supporting bone. This did not appear to interfere with mastication. Minimal eating was noted for the first 36 hours, but marked improvement was noted over the next several days. The wallaby would use the front feet to grasp food items and bring it to the right side of the jaw for mastication. The animal appeared to gain weight and was eating normally with minimal problems. Antibiotics were discontinued 20 days after surgery.
However, 28 days after surgery, the surgical site became infected. Additional therapy was initiated with daily flushing of the site with hydrogen peroxide, combined with 5 mg/kg enrofloxacin IM BID via blowdart. The infection spread through fascial planes to the tracheotomy incision, and the animal began to lose weight. Due to an overall poor prognosis, the wallaby was euthanatized.
Necropsy revealed abscess of the deeper mandibular tissues and ventral cervical musculature. Acinetobacter calcoaceticus, Klebsiella pneumoniae, and Streptococcus sp. were identified from aerobic cultures. All organisms were sensitive to enrofloxacin and trimethoprim/sulfadiazine. Bacteroides fragilis was identified from anaerobic culture, which was sensitive to penicillin. Tissues of all organs were sectioned, placed in 10% neutral buffered formalin, embedded in paraffin, and sectioned at 5 µm. Abscess of the fascial tissues with necrotic material surrounded by a wide zone of neutrophils and an outer zone of macrophages and neutrophils was observed.
Discussion
Despite secondary bacterial infection, which is a potential with any surgery, we considered this procedure a success. The results were aesthetically pleasing, the animal returned to normal eating habits, and initial weight gain was noted. The Cole technique for intubation worked well. Basically, a small incision is made over the caudal larynx after sterile preparation of the skin. A thin, sterile stylet is inserted in a retrograde direction through the skin and into the trachea. The stylet is advanced along the trachea, past the glottis, and out of the oral cavity. The endotracheal tube is placed over the stylet and advanced in a normograde fashion into the trachea until the juncture of the stylet and endotracheal tube is encountered. The stylet is then removed, the endotracheal tube is advanced and insufflated in a standard manner.
This radical surgical option may be successful in macropods affected with refractory cases of necrobacillosis, oral neoplasms, or non-repairable trauma. The median shift of the right mandible caused no initial concerns, as the wallaby appeared to adapt well to the loss of the left mandible. Long-term concerns with proper mastication and dental diseases were discussed as potential future complications. Intravenous sodium iodine therapy was not elected in this case but has been utilized without success in an additional case of necrobacillosis in a Bennett’s wallaby and a greater kudu (Tragelaphus strepsiceros) (unpublished data). Secondary bacterial infections may be difficult to control, and appropriate antibiotic therapy is warranted. Pain relief should be addressed with such an extensive surgery. In this case, administration of butorphanol appeared to accelerate the return to normal behavior and eating habits.
A comprehensive review of management practices and diet is currently being conducted as an aid in preventing future cases of necrobacillosis in the macropod collection at the Kansas City Zoological Gardens.
Acknowledgments
The authors would like to thank the animal care staff at the Kansas City Zoological Gardens for their help in resolving this case.
Literature Cited
1. Ayers, K.M., F.M. Garner, and L.A. Griner. 1971. Disseminated nocardiosis in a North African antelope. J Am Vet Med Assoc 159:611–613.
2. Burton, J.D. 1981. Studies into aspects of “lumpy jaw” in macropods. PhD thesis, Melbourne University, Melbourne, Australia.
3. Butler, R. and J.D. Burton. 1986. Bacterial diseases. In: Fowler, M.E. (ed.) Zoo and Wild Animal Medicine. W.B. Saunders Co., Philadelphia, PA, Pp. 572–574.
4. Hume, I.D. and P.S. Barboza. 1993. Designing artificial diets for captive marsupials. In: Fowler, M.E. (ed.). Zoo and Wild Animal Medicine. Current Therapy 3. W.B. Saunders Co., Philadelphia, PA, Pp. 282–283.
5. Sanson, G.D. 1989. Morphological adaptations of teeth to diets and feeding in the Macropodoidea. In: Grigg, G., P. Jarmen, and I. Hume (eds.) Kangaroos, Wallabies and Rat-Kangaroos. Surrey Beatty, Sydney, Australia, Pp. 151.
6. Walker, R.D. 1993. Actinobacillosis and actinomycosis. In: Howard J.L. (ed.) Current Veterinary Therapy 3: Food Animal Practice. W.B. Saunders Co., Philadelphia, PA, Pp. 534–535.
7. Wallach, J.D. and W.J. Boever. 1983. Disease of Exotic Animals. W.B. Saunders Co., Philadelphia, PA, Pp. 264, 588–591, 640.
8. Withrow, S.J. and D.L. Holmberg. 1983. Mandibulectomy in the treatment of oral cancer. J. Am. Anim. Hosp. Assoc. 19:273.