An 11-year-old castrated male mixed breed (dog 1) was evaluated for an 11-day history of progressive paraparesis. The dog traveled extensively throughout the United States and was frequently exposed to ticks. Physical examination abnormalities included a 1-cm subdermal nodule on the caudolateral aspect of the thorax. Neurologic deficits were consistent with a T3–L3 myelopathy, including ambulatory pelvic limb ataxia and paraparesis with intact pelvic limb reflexes, and spinal hyperpathia in the midlumbar area. A CBC, serum biochemical profile, and urinalysis were within reference ranges. Cytologic examination of the subdermal mass revealed pyogranulomatous inflammation. Thoracic radiographs revealed a mild bronchiolar pattern.
The dog was anesthetized for radiography and computed tomography (CT) of the thoracolumbar spine. No significant abnormalities were noted on radiographs. The CT revealed an extradural soft-tissue mass (Fig 1A) that was hyperattenuating relative to the spinal cord, and enhanced uniformly following contrast administration (iothalamate sodium [0.45 mL/kg], IV). The mass extended irregularly from the caudal L3 to the cranial L5 vertebral bodies, resulting in significant spinal cord compression in the L4 midbody region and focal bone resorption of the L4 vertebral body (Fig 1B). Differential diagnoses for the CT abnormalities included soft-tissue sarcoma (nerve sheath neoplasia, fibrosarcoma), extradural meningioma, lymphoma, or inflammatory granuloma.
A right hemilaminectomy defect extending from L3 to L5 was created, which revealed a tan, friable extradural mass extending from L3 to L5. After removal of the extradural mass in a piecemeal fashion, multifocal intradural masses were visualized between L4 and L5, which prompted performance of a regional durectomy and subsequent removal of the intradural masses using blunt dissection. Rhizotomy of the L4 dorsal and ventral roots was performed because of gross thickening of visualized intra- and extradural portions of the nerve roots and nerve. The extradural mass, intradural masses, dura, nerve, and nerve roots were submitted for histopathologic examination. The hemilaminectomy defect was covered with gelfoam and the surgical wound was closed routinely.
Histopathologic examination of extra- and intradural portions of the masses revealed abundant fibrous tissue with multiple infiltrative foci consisting of primarily neutrophils with fewer macrophages and giant cells admixed with fibrin and necrotic debris (Fig 2A). There were lymphocytes and plasma cells in the periphery of the lesion. The L4 spinal nerve and nerve roots were infiltrated with islands of lymphocytes, plasma cells, and few neutrophils (Fig 2B). No infectious organisms were detected in excised tissue sections subjected to Gram, Warthin-Starry silver, acid-fast, or periodic acid Schiff (PAS) stains. The final histopathologic diagnosis was pyogranulomatous, lymphoplasmocytic meningoradiculoneuritis.
Serologic assays for blastomycosis, coccidiomycosis, neosporosis, and toxoplasmosis antibodies were negative, as was a cryptococcal capsular antigen test. By indirect fluorescent antibody (IFA) testing, the dog was seroreactive to Bartonella vinsonii subsp. berkhoffi antigens (titer 1 : 64).b
Postoperative care included morphine (0.25 mg/kg SC q6h), deracoxib (2.7 mg/kg PO q24h), and lactated Ringers solution (2.75 mL/kg/h IV). Paraparesis improved the day after surgery, and the dog was discharged 5 days later. The owner was instructed to administer azithromycin (13.9 mg/kg PO q24h for 5 days followed by q48h for 23 days). The neurologic examination was normal on recheck day 8 after surgery. B. vinsonii subsp. berkhoffi DNA was detected in an EDTA-anticoagulated blood sample collected at that time using real-time polymerase chain reaction (PCR).b Real-time PCR for Bartonella species performed on formalin-fixed, paraffin-embedded tissues were negative.b,c The histologic findings, serology, and PCR results were interpreted as consistent with active B. vinsonii subsp. berkhoffi infection.
Four months later, no clinical abnormalities were present on reexamination. A repeated B. vinsonii subsp. berkhoffi antibody titer was <1 : 16, and PCR on EDTA-anticoagulated blood was negative.b A CT examination of the surgical site was performed under anesthesia and revealed a scant amount of contrast enhancing soft tissue material in the dorsal aspect of the L4 vertebral body in the region of previously noted bone resorption, with no evidence of spinal cord compression (Fig 3). Therapy with azithromycin was repeated (7 mg/kg PO q12h for 6 weeks), based on the CT results. The dog remains clinically normal to date (29 months after surgery).
An 8-year-old, spayed female Shetland sheepdog (dog 2) was referred with a 5-week history of progressive paraparesis despite prednisone therapy (1.3 mg/kg/day PO). The dog had been observed to have multiple infestations with fleas and ticks. Results of a CBC, serum biochemical profile, urinalysis, and thoracolumbar radiographs performed before referral revealed no significant abnormalities.
Physical examination abnormalities included multiple, variably sized (0.3–1 cm in diameter) subcutaneous nodules located in the thoracic, flank, and inguinal areas, and palpable hepatomegaly. Neurologic abnormalities were consistent with a T3–L3 myelopathy and included ambulatory pelvic limb ataxia and paraparesis, exaggerated pelvic limb spinal reflexes, a normal cutaneous trunci reflex, and spinal hyperpathia at the L2 level.
Fine needle aspirates of nodules from the flank and inguinal areas were cytologically consistent with pyogranulomatous inflammation. Additional cytologic specimens stained with Gram and acid-fast stains did not result in the visualization of organisms. Abdominal ultrasonography revealed a diffusely hyperechoic hepatic parenchyma. No significant abnormalities were noted on thoracic radiographs.
The dog was anesthetized for thoracolumbar magnetic resonance imaging, which revealed an intradural-extramedullary mass lesion extending from the L3 vertebra cranially to exit the left L2–L3 intervertebral foramen that was contiguous with a focal nodular thickening of the left L3 spinal nerve. Relative to skeletal muscle, the mass was isointense on T1 images and hyperintense on T2 images, and demonstrated marked homogenous enhancement on postcontrast (gadolinium-DTPA [0.1 mmol/kg], IV) T1 images. Intradural portions of the mass were associated with spinal cord compression in the L2–L3 region. Lumbar cerebrospinal fluid (CSF) was consistent with a mild mixed cellular pleocytosis, characterized by nondegenerate neutrophils and lymphocytes. Nerve sheath neoplasia and meningioma were considered the primary differential diagnoses. The dog was aseptically prepared for an L2–L3 hemilaminectomy and excisional biopsy of one of the lateral thoracic subcutaneous nodules.
After creation of a hemilaminectomy defect at L2–L3, a reddish-gray subdural mass centered over the body of L3 was visualized. The mass coursed to the caudal limits of hemilaminectomy, so the defect was extended to involve L3–L4. A durectomy extending from L2 to L4 was performed, which revealed a reddish, friable, intradural-extramedullary mass, which was subsequently removed in a piecemeal fashion. Both intradural and extradural portions of the L3 dorsal and ventral nerve roots and nerve appeared thickened and nodular, and an L3 rhizotomy was performed. The excised mass was submitted for histopathologic analysis and aerobic and fungal cultures. The hemilaminectomy defect was covered with autologous fat, and the surgical site was closed routinely.
Biopsies of the intradural mass, excised spinal nerve and nerve roots, and subcutaneous nodule were consistent with pyogranulomatous and lymphoplasmocytic meningitis, radiculoneuritis, and panniculitis, respectively. No etiologic agents were detected following Gram, acid-fast, and PAS staining procedures.
Postoperatively, morphine (0.4 mg/kg SC q4–6h) and lactated Ringer's solution (3 mL/kg/h IV) were administered for 36 hours. Serology was negative for blastomycosis and neosporosis. CSF assays for Toxoplasma gondii antibodies and crytococcal capsular antigen were negative. The dog was seropositive to B. vinsonii subsp. berkhoffi (titer 1 : 256).b Real-time PCR for Bartonella species DNA, performed on EDTA-anticoagulated plasma and freshly excised portions of the intradural mass, were both positive for B. vinsonii subsp. berkhoffi DNA.c Aerobic and fungal cultures of the excised mass, CSF, and the skin nodule did not yield bacterial or fungal growth. The dog was discharged to the owners 72 hours after surgery with instructions to administer azithromycin (11.7 mg/kg PO q24h for 6 weeks), and taper the prednisone (0.6 mg/kg PO q24h).
Thirteen days after surgery, the subcutaneous nodules had largely resolved, with only 2 small nodules being noted in the inguinal region. The dog was ambulating with mild pelvic limb ataxia, and the owners were instructed to continue the azithromycin for 3 more weeks, and reduce the prednisone therapy to 0.6 mg/kg PO q48h for 1 week. Six months later, the dog was normal on recheck examination. The serum B. vinsonii antibody titer was < 1:16, and Bartonella PCR using EDTA-anticoagulated blood was negative.b Another recheck performed 17 months postoperatively identified no physical abnormalities.
A 9-year-old, castrated male Miniature Schnauzer was evaluated for an 18-day history of progressive paraparesis. The dog lived primarily indoors and did not travel extensively. Physical examination abnormalities included multiple cutaneous nodules over the right quadriceps and right popliteal lymphadenopathy. Neurologic deficits were consistent with a T3–L3 myelopathy (paraplegia, clonic pelvic limb reflexes, intact nociception, and cutaneous trunci reflex absent caudal to L1). A CBC, biochemical profile, urinalysis, and fine needle aspirates of the right popliteal lymph node and cutaneous nodules were performed. The CBC and urinalysis were unremarkable. Serum biochemical abnormalities included increased alanine aminotransferase (166 U/L; reference range, 17–66 U/L) and ALP activities (234 U/L; reference range, 14–105 U/L), and hyperglobulinemia (4.4 g/dL; reference range, 2.2–4.0 g/dL). The lymph node and cutaneous nodule aspirates were consistent with reactive hyperplasia and pyogranulomatous inflammation, respectively.
The dog was anesthetized for a thoracolumbar CT, which revealed a ventral extradural, homogenously contrast enhancing mass lesion causing spinal cord compression in the L1–L2 region. Lumbar CSF analysis was consistent with a lymphocytic pleocytosis. Following a left L1–L2 hemilaminectomy, a tan, friable, extradural mass was visualized and removed. Portions of the mass were adherent to the dura, which was locally excised, and the surgical site was closed routinely.
Postoperative treatment consisted of morphine (0.4 mg/kg SC q4–6h) and urinary bladder expression q8h. The excised mass was histologically consistent with pyogranulomatous meningitis, with no etiologic agents visualized. An EDTA-anticoagulated blood sample was positive for B. vinsonii subsp. berkhoffi DNA using real-time PCR.c
Five days postoperatively, the dog was discharged with weak voluntary motor activity. The owners were instructed to begin treatment with clindamycin (13 mg/kg PO q12h) and enrofloxacin (5.9 mg/kg PO q12h). On recheck 10 days later, the subcutaneous nodules had diminished in size, and the dog was able to ambulate with sling assistance and urinate voluntarily. The clindamycin and enrofloxacin were continued for 6 weeks. Eight weeks later, the referring veterinarian reported that the cutaneous nodules and lymphadenopathy had resolved, and the dog was ambulatory with mild ataxia.
To the authors' knowledge, these are the first dogs with B. vinsonii subsp. berkhoffi associated with inflammation involving the spinal meninges, nerve roots, and nerves. Although direct causation has not been established, Bartonella spp. have been associated with various canine nervous system disorders, including myelopathy,1 neutrophilic or granulomatous meningoencephalitis,2 anterior uveitis and choroiditis,3 and meningitis.4Bartonella may affect any topographical portion of the nervous system, resulting in meningoencephalitis, transverse myelitis, vertebral osteomyelitis associated with extradural abscessation, and focal pyogranulomatous meningoradiculoneuritis.1,2,4–6
Proposed mechanisms for Bartonella-associated neurologic disease include direct bacterial invasion and indirect toxin-, immune-, or vasculitis-mediated injury.7 In in vitro studies using feline microglial cells, B. henselae was able to invade microglia, but not astrocytes, and intracellular infection did not induce ultrastructural microglial changes.8 The cellular localization of Bartonella spp. within specific nervous tissues has not been studied, and the extent to which organisms can persist within cells of the CNS is unknown. Experimental infection of cats with B. henselae and B. clarridgeiae suggests that CNS tissues can harbor Bartonella during periods of abacteremia.9
All dogs in this series had concurrent pyogranulomatous dermatitis or panniculitis. Bartonella spp. have been associated with granulomatous inflammation in extraneural canine tissues, including lymphadenitis, rhinitis, panniculitis, and polysystemic granulomatous disease.4,10–12Bartonella species DNA was found in the blood of a dog with α1-proteinase inhibitor deficiency, panniculitis, polyarthritis, and meningitis.4 The role of Bartonella as a cause or cofactor in the development of panniculitis in dogs requires additional investigation.
Diagnosing bartonellosis can be difficult. Unless immunocompromised, the Warthrin–Starry silver stain is insensitive for the diagnosis of Bartonella infection in humans.13 Isolation of Bartonella species by conventional blood culture also has a low sensitivity in dogs and humans.14,15 In a study of canine endocarditis, 5/18 dogs demonstrated seroreactivity to Bartonella spp. antigens and had postmortem evidence of Bartonella spp. DNA in diseased aortic valves, although only 1/5 dogs was positive by conventional blood culture.15 Because of the chronic, insidious nature of bartonellosis, prior antibiotic treatment complicates the diagnosis of Bartonella infection by making culture and PCR less sensitive.16,17 Although serology can be useful to establish prior exposure to or active infection with Bartonella species, nearly half of infected dogs can be seronegative by IFA testing.4,14,16 Combinations of pre-enrichment liquid culture in an insect cell culture–based growth medium with PCR detection of Bartonella spp. resulted in enhanced detection or isolation of several Bartonella spp. as compared with conventional culture techniques.14
The ideal antibiotic for the treatment of Bartonella infections in dogs is unknown. Bartonella isolates have demonstrated in vitro susceptibility to β-lactams, aminoglycosides, macrolides, doxycycline, and rifampin.18 Tetracyclines, fluoroquinolones, β-lactams, and combinations of these drugs have been used to treat dogs and cats with Bartonella spp. infections.2,11,17 However, in vivo treatment becomes more difficult as Bartonella species have been found within erythrocytes, macrophages, endothelial cells, microglial cells, pericytes, and neutrophils in cell cultures and tissues obtained from multiple animal species.8 Using antibiotics that accumulate within leukocytes, such as azithromycin and fluoroquinolones, may prove beneficial because these cells can migrate to infectious foci such as granulomatous lesions.19 Evidence suggests that specific strains of B. henselae can be resistant to macrolides.20 One study indicated that enrofloxacin was more efficient at eliminating Bartonella-associated bacteremia than doxycycline, but neither drug eliminated bacteremia in all experimentally infected cats.17 It has been speculated that the variation in antimicrobial therapeutic outcome may not be solely related to the efficacy of each antibiotic, but to the immune-mediated changes caused by Bartonella species.21
The outcomes of the dogs in this series provide support for fluoroquinolone or azithromycin usage for Bartonella infections. In this report, additional decompressive surgery also allowed for rapid improvement in neurologic deficits. Surgical decompression, in combination with appropriate antimicrobial therapy, is indicated in humans and dogs with specific focal infectious spinal cord diseases.5,22 Although not evaluated in this study, medical management alone might result in progressive neurological deterioration or residual dysfunction.
Bartonella spp. infections should be considered as a differential diagnosis in dogs with thoracolumbar myelopathy, especially if accompanied by a nodular dermatosis. Serology, pre-enrichment blood culture, and PCR from tissues should be used to support the diagnosis. Treatment through surgical decompression with azithromycin or doxycycline-enrofloxacin combinations may be appropriate for Bartonella-associated pyogranulomatous inflammation in dogs. Prospective studies are needed to determine the incidence of focal neurologic lesions in animals and humans that are positive for Bartonella spp. based on serology, culture, or PCR.