Follow-up

About a week after the antimicrobial therapy was changed and the castration performed, the owner reported that the dog's lameness had resolved and the spinal pain had greatly diminished. On recheck examination at the TVMC four weeks after the diagnosis, lameness was not evident, and palpation along the vertebral column revealed no pain. The dog had gained 4 lb (1.8 kg) and was no longer febrile. The owner reported that the dog's activity level and appetite had markedly increased in the previous weeks. On repeat vertebral radiographs, there was increased radiopacity of the previously noted lytic lesions of the thoracic and lumbar vertebrae. The etodolac therapy was discontinued at this time.

At a second recheck examination 10 weeks after the diagnosis, the dog was asymptomatic and had gained another 4 lb. We again obtained radiographs of the affected regions of the vertebral column. The lumbar vertebral lesions showed further improvement; the lytic lesions were becoming less apparent. The thoracic vertebral lesions were unchanged compared with the previous radiographs. We advised the owner to continue treatment, but the owner elected to discontinue antimicrobial therapy. To monitor for recurrence, we recommended recheck examinations and vertebral radiography every three months for one year or immediately if any of the original clinical signs were observed.

Four months after the antimicrobial therapy was discontinued, the dog was presented to the TVMC for evaluation of spinal pain and lethargy. The owner reported that the dog had been active and nonpainful for the previous 16 weeks and that the onset of the current signs was acute. On physical examination, severe pain was noted on palpation of the caudal thoracic and lumbosacral vertebral columns. The dog's body weight was unchanged from the previous examination. Its rectal temperature was normal, and no abnormalities were identified on neurologic examination.

Diagnostic tests and treatment

A thoracic and lumbosacral vertebral radiographic examination was repeated, but no changes were noted compared with the radiographs obtained on the previous visit. Urine was collected by cystocentesis for analysis and quantitative bacterial culture and antimicrobial susceptibility testing. Blood was collected for B. canis serology and aerobic bacterial culture. The results of urinalysis and a sediment examination were unremarkable. A Brucella species (800 cfu/ml) was isolated on urine culture. A Brucella species was also identified on aerobic blood culture. The antimicrobial susceptibility of these isolates was identical to the B. canis cultured on initial presentation. Serologic titer results indicated exposure to B. canis (1:200 on both the immunofluorescent antibody and tube agglutination tests).

After we discussed the long-term prognosis and zoonotic concerns, the owner elected to restart treatment. Therapy with enrofloxacin (15 mg/kg orally once a day) and doxycycline (5 mg/kg orally b.i.d.) was reinitiated for an empirically chosen treatment course of at least 12 months. Etodolac (10 mg/kg orally once a day) and strict cage rest were recommended for one month. As before, the dog responded rapidly and dramatically to treatment. The owner reported that the dog was asymptomatic after one week of antimicrobial therapy.

Follow-up

After this recurrence of the dog's clinical signs, three recheck examinations have been performed about every three months. Over this period, the dog has remained asymptomatic. During each recheck, palpation of the spine has revealed no pain, and the dog has remained afebrile. It has gained about 2 lb (0.9 kg) at each recheck.

On the first recheck during this period, radiographs of the thoracic and lumbar spine showed no changes in the lumbar diskospondylitis lesions, but increased bone lysis was present at T5-T6. Treatment at this time was unaltered except for increasing the enrofloxacin dose to adjust for weight gain. On the second recheck examination, immunofluorescent antibody and tube agglutination tests were repeated, and the results of each were 1:200. The dog's body condition score was 4/5, and the treatment was unaltered. On the third recheck, immunofluorescent antibody and tube agglutination test results had decreased to 1:100 (interpreted as a weak seropositive result), and antimicrobial treatment was continued.

The dog has not been rechecked in the subsequent four months but continues to receive antimicrobial therapy. The owner reported that the dog has remained asymptomatic and is doing well.