Introduction

Approximately 15 percent of bone infections in man involve the spine. For the most part the mode of introduction of organisms is hematogenous and rarely associated with direct extension from adjacent areas. Hematogenous Infections of the spine characteristically involve the ventral structures, and predominantly affect the intervertebral disk and adjacent vertebral end plates.¹ Because these Infections most frequently begin within the body of the vertebra, adjacent to the end plates, they may be most accurately defined as osteomyelitis.¹ Depending on the pathway of extension from the end plate zone, an ensuing diskitis, paravertebral abscess, epidural abscess, meningitis, or myelitis may occur.²

Several terms have been used to describe this syndrome including diskitis, intervertebral disk infection, spondylitis, vertebral osteomyelitis, diskospondylitis³ and intradiskal osteomyelitis.¹ The latter two terms most accurately capture the actual disease process--a concurrent intervertebral disk infection and vertebral osteomyelitis of contiguous vertebrae. Diskospondylitis (vertebral osteomyelitis) was recognized in man as early as 1887.³ A similar disease was not reported in dogs until the 1960s.⁴

Causes of intradiskal and vertebral osteomyelitis in dogs include foreign body migration, fungal and bacterial infection. Staphylococcus aureus is the most common organism associated with this disease having been isolated by culture of either blood, urine, or bone from 19 of 32 dogs in one reported series.⁵ Brucella canis, Corynebacterium spp., Pasteurella multocida, Escherichia coli, and Proteu spp. have also been isolated from affected dogs. Fungal agents identified in dogs affected with either diskospondylitis vertebral osteomyelitis include Paecilomyces spp., Aspergillus terreus, Nocardia spp., Eusarium spp., and Mucor spp.

Clinical signs in dogs affected with diskospondylitis include hyperesthesia, paresis, stilted gait, depression, and weight loss. In the previously mentioned series of 32 canine cases⁵ other sites of infection or possible predisposing causes were present in 14 dogs. Urinary tract infection was present in 12 dogs; 10 of these were bacterial urine culture-positive; 1 had evidence of chronic nonsuppurative papillitis at necropsy, and 1 had evidence of glomerulonephritis or renal biopsy. Histopathologic evidence of: epididymitis and orchitis were present in one dog seropositive for B canis. There was no pattern of particular disk space involvement or region of' the spinal column affected.⁵

Case Report

A 20-year-old male Atlantic Bottle-nosed Dolphin (Tursiops truncatus) first examined by the referring veterinarian in May because of a "'tennis size lump on the right side of the body approximately six inches anterior the tail fluke. No treatment or diagnostic tests were performed at this By September the lesion had more than doubled in size. The animal was reluctant to move or perform, was reported to be in obvious pain, and had a reduced appetite. Radiographs of the affected area revealed involvement of the vertebral column with rarefaction of bone, collapse of the disk space, and proliferative bony changes adjacent to the intervertebral disk space. The swelling was lanced in an attempt to achieve drainage. Cultures taken at this time isolated a Staphylococcus spp. The animal was treated with cefazolin sodium (Ancef) for five days and Cephalexin (Keflex) for six additional weeks. Improvement was noted in the clinical signs after four days of therapy. Follow up radiographs revealed an improvement in the radiographic appearance of the lesion.

The animal has returned to full activity including his duties as a show performer.

Discussion

In both man and dogs urinary tract infections are thought to serve as primary foci of infection. Bacteria were initially thought to spread from the urinary system to the vertebral column through the venous plexus. However, more recent work of vertebral arterial and venous supply has shown that bacteria in all likelihood gain access to the vertebrae through the arterial system. These same studies suggested that infection originates in the vertebral metaphyseal area rather than the disk.

The predominant clinical feature of vertebral and intradiskal osteomyelitis is that of excruciating pain. Analgesics alone will often provide a marked improvement in the clinical manifestations of this syndrome.

If an organism is not isolated from any tissue then initial treatment should be focused against Staphylococcus aureus.⁶ The most efficacious, antibiotics are cephalosporin, cloxacillin, chloramphenicol, and gentamicin. If there is no evidence of clinical recovery within 7 to 10 days, the administration of a different antibiotic should be considered.

Antibiotic administration should be continued for a minimum of six weeks. The animal should be "rested" during the treatment period as movement only discourages the healing process.

References

1.  Johnson, R.G. and Prata, R.G.: Intradiskal osteomyelitis: A conservative approach, Jr. Am. An. Hosp. Assoc., 19:743, 1983.

2.  Bailey, R. and Wayne, M.D.; The Cervical Spine. Lea and Febiger, Philadelphia, 1974.

3.  Kornegay, J.W.: Canine diskospondylitis, Compendium on Continuinq Education, 1:930, 1979.

4.  Geary, J.C.: Canine spinal lesions not involving discs, Jr. Am. Vet. Med. Assoc., 155:2038, 1969.

5.  Kornegay, J.N. and Barber, D.L. Med. Assoc., 1977: 337, 1980.

6.  Gilmore, D.R.: Lumbosacral diskospondylitis in 21 dogs, Jr. Am. An. Hosp, Assoc., 23:57, 1987.