An 8-month-old male greater flamingo (Phoenicopterus roseus) was presented in ventral recumbency after a sudden onset of bilateral nonambulatory pelvic limb paresis (day 1). There were no preceding abnormalities in demeanor, appetite, and gait. On physical examination, the flamingo weighed 2.32 kg (5.10 lb) and had a pectoral muscle condition score of 2.5/5. The flamingo had voluntary movement, normal superficial pain response, and normal conscious proprioception in both pelvic limbs. Paresis was considered the bird's only problem at this time.
Because infectious neurologic disease could not be ruled out, treatment for bacterial infection of the nervous system and supportive care were commenced. Meloxicama and enrofloxacinb (1:10 dilution to reduce the chance of muscular necrosis) were administered IM. Oral treatment with these drugs was initiated on day 2. Because there was no change in the flamingo's condition on day 3, IV fluid therapy with lactated Ringer solutionc was started; itraconazoled was also administered orally beginning on day 3 to prevent aspergillosis associated with prolonged antimicrobial treatment. Neurologic examination was repeated.
What is the problem? Where is the lesion? What are the most probable causes of this problem? What is your plan to establish a diagnosis? Please turn the page.
Assessment Anatomic diagnosis
| Problem | Rule out location |
|---|---|
| Pelvic limb paresis | Thoracolumbar portion of the spinal cord |
| Diminished conscious proprioception | Thoracolumbar portion of the spinal cord |
| Exaggerated spinal reflexes | Thoracolumbar portion of the spinal cord |
Likely location of 1 lesion
Thoracolumbar portion of the spinal cord
Etiologic diagnosis—The important differential diagnoses for paresis in this flamingo included rhabdomyolysis, bacterial disease, fungal disease (aspergillosis), viral disease (eg, avian influenza virus, avian bornavirus, or Newcastle disease virus infection), neurologic disease (neuritis, meningitis, or diskospondylitis), degenerative disease (gangliosidosis or avian vacuolar myelinopathy), neoplasia (involving the spinal cord or vertebral column, testicles [or ovaries in a female bird], or kidneys), and traumatic injuries (soft tissue or orthopedic trauma). A manual CBC and in-house plasma biochemical profile were performed (to provide a minimum diagnostic database). The flamingo was manually restrained, and radiography of both pelvic limbs was undertaken (to detect orthopedic injuries or other radiographic abnormalities).
Diagnostic test findings—The clinicopathologic analyses revealed no abnormalities. Radiography of both of the bird's pelvic limbs revealed no orthopedic injuries or other radiographic abnormalities. The absence of high plasma creatine kinase and aspartate aminotransferase activities indicated that rhabdomyolysis and muscular injury were not likely causes of the bird's paresis. A lack of any palpable swelling of the pelvic limbs indicated that soft tissue (tendon or ligament) injuries were unlikely.
Development of diminished conscious proprioception and hyperesthesia on day 3 narrowed the differential diagnosis list to upper motor neuron disease (meningitis or diskospondylitis). Treatment with gabapentine (10 mg/kg [4.5 mg/lb], PO, q 12 h) was commenced to provide more effective analgesia for perceived neuropathic pain. Fluid therapy was continued at 4 mL/kg/h (1.8 mL/lb/d) until day 5, when the flamingo was observed to drink voluntarily. Because the flamingo remained anorexic, it required tube feeding twice a day, which was continued throughout the period of hospitalization.
There was no improvement in the flamingo's neurologic status, and a repeated CBC and plasma biochemical profile performed on day 7 revealed an increase in the WBC count, compared with findings on day 1, but the value remained within the reference interval. Worsening infection was the likely cause of the mild heterophilia and monocytosis that were also detected.
On day 10, the flamingo was anesthetized and underwent CT with a 32-slice multidetector CT unitf to assess the bird's spinal cord and vertebral column. Transverse images of the spinal cord and vertebral column were obtained in soft tissue and bone windows both with slice thicknesses of 1.25 and 0.625 mm before and after IV administration of nonionic iodinated contrast mediumg (600 mg/kg [272.7 mg/lb]). The CT images were reconstructed in sagittal and dorsal planes in different windows. The entire spinal cord and vertebral column from the occiput to the pygostyle were scanned; images of the coelomic cavity and the proximal aspect of the pelvic limbs were obtained. There was widening of the T5-6 intervertebral disk space, compared with the other intervertebral disk spaces (Figure 1). The caudal endplate of T5 and cranial endplate of T6 were irregular and appeared lytic, especially at the caudal aspect of T5, and there was moderate sclerosis in the caudal endplate of T5 that was more pronounced on the left side. There was substantial contrast enhancement (precontrast attenuation, 120 HU; postcontrast attenuation, 170 HU) at the ventral aspect of the T5-6 intervertebral disk space, suggestive of inflammation. However, there was no visible compression of the spinal cord. No other abnormalities were evident on the CT images. The CT findings suggested the presence of some diskospondylitis at the level of the T5-6 intervertebral disk space.
Sagittal (A), transverse (B), and dorsal (C) CT images of an 8-month-old greater flamingo (Phoenicopterus roseus) that was presented in ventral recumbency after a sudden onset of bilateral nonambulatory pelvic limb paresis. The images were obtained 10 days after the initial evaluation of the flamingo by use of a bone window after the bird received an IV injection of contrast medium. Notice the widening of the T5-6 intervertebral disk space, moderate sclerosis of the caudal endplate of T5 (left side more affected than the right side), moderate lysis of the caudal endplate of T5 (arrows), and mild lysis of the cranial endplate of T6.
Citation: Journal of the American Veterinary Medical Association 257, 7; 10.2460/javma.257.7.703
Sagittal (A), transverse (B), and dorsal (C) CT images of an 8-month-old greater flamingo (Phoenicopterus roseus) that was presented in ventral recumbency after a sudden onset of bilateral nonambulatory pelvic limb paresis. The images were obtained 10 days after the initial evaluation of the flamingo by use of a bone window after the bird received an IV injection of contrast medium. Notice the widening of the T5-6 intervertebral disk space, moderate sclerosis of the caudal endplate of T5 (left side more affected than the right side), moderate lysis of the caudal endplate of T5 (arrows), and mild lysis of the cranial endplate of T6.
Citation: Journal of the American Veterinary Medical Association 257, 7; 10.2460/javma.257.7.703
Sagittal (A), transverse (B), and dorsal (C) CT images of an 8-month-old greater flamingo (Phoenicopterus roseus) that was presented in ventral recumbency after a sudden onset of bilateral nonambulatory pelvic limb paresis. The images were obtained 10 days after the initial evaluation of the flamingo by use of a bone window after the bird received an IV injection of contrast medium. Notice the widening of the T5-6 intervertebral disk space, moderate sclerosis of the caudal endplate of T5 (left side more affected than the right side), moderate lysis of the caudal endplate of T5 (arrows), and mild lysis of the cranial endplate of T6.
Citation: Journal of the American Veterinary Medical Association 257, 7; 10.2460/javma.257.7.703
Microbial culture of a blood sample was planned, even though antimicrobial treatment of the flamingo had already been started. In the culture system used, a positive blood culture result could still be obtained if the infective bacteria were resistant to enrofloxacin or if enrofloxacin did not reach therapeutic concentration at the infected intervertebral disk. A 6.0-mL sample of blood was collected after the skin over the flamingo's right jugular vein was aseptically prepared with chlorhexidine surgical scrub solution. The blood sample underwent bacterial culture and antimicrobial susceptibility testing.
Owing to the flamingo's lack of clinical response to enrofloxacin, the treatment protocol was changed on day 11 to trimethoprim-sulfamethoxazoleh (24 mg/kg [10.9 mg/lb], PO, q 12 h), itraconazole, meloxicam (1 mg/kg [0.45 mg/lb], PO, q 12 h), and gabapentin.
The meloxicam dosage was lowered to prevent renal toxicosis, which may result from an extended course of treatment with this drug. Gabapentin administration was discontinued on day 18. The blood culture results were received on day 19. Serratia marcescens had been isolated from the blood sample. The organisms were susceptible to ceftizoxime, cotrimoxazole, enrofloxacin, gentamicin, chloramphenicol, doxycycline, and trimethoprim but resistant to amoxicillin–clavulanic acid, cephalothin, and tetracycline. The fact that the bacteria were susceptible to both enrofloxacin and trimethoprim indicated that the change in antimicrobial administration may not have changed the flamingo's treatment outcome.
Physical rehabilitation (sessions of 15 to 30 minutes’ duration each) was also initiated twice daily starting on day 19. The physical therapy included combinations of walking with support on a road and an area of grass, passive range of motion exercises with the flamingo positioned in a sling, and swimming.
The flamingo developed a head tilt without nystagmus on day 31. Any asymmetry of the vestibular system (which is composed of the vestibular portion of cranial nerve VIII that originates from the semicircular canals of the inner ear and the nuclei of cranial nerve VIII in the medulla) can cause a head tilt. The important differential diagnoses for the flamingo's head tilt included bacterial infection, degenerative changes, trauma, toxins, and neoplasia affecting the vestibular system as well as central vestibular disease and peripheral vestibular disease, such as otitis media or otitis interna. On day 33, a CBC and plasma biochemical profile were repeated; a blood sample was collected for microbial culture. The clinicopathologic analyses revealed that the flamingo had a high WBC count, compared with findings on day 1, with very mild monocytosis; the PCV had decreased. Microbial culture of the blood sample yielded no bacteria. These test results ruled out most of the differential diagnoses for a head tilt, leaving trauma as the most likely cause. Because the flamingo remained nonambulatory and inappetent with no improvement in the rest of its condition despite treatment, euthanasia was elected and performed by injection of euthanasia solution in the right medial metatarsal vein on day 38. A complete necropsy was performed 2 hours after euthanasia, which confirmed severe lymphoplasmacytic diskospondylitis, periostitis, and ganglionitis at the level of the T5-6 intervertebral disk space with associated intervertebral disk protrusion.
Comments
In birds, diskospondylitis has only been described for a yellow-eyed penguin (Megadyptes antipodes), an African black-footed penguin (Spheniscus demersus), and a white stork (Ciconia ciconia),1–3 to the authors’ knowledge. Additionally, a very similar case involving a juvenile peregrine falcon (Falco peregrinus) was reported, but owing to the bird's age and the presence of kyphosis, the diagnosis made was vertebral osteomyelitis, which is more commonly reported as affecting poultry.4–7 The differentiation between diskospondylitis and vertebral osteomyelitis is likely to be of academic interest only.8
Localization of a vertebral column lesion is easier in birds than it is in mammals because avian spinal nerves pass through the vertebral foramina laterally and the segment of the spinal cord is equivalent to the segment of the vertebral column.9 Therefore, in birds, the level at which neurologic deficits are identified is usually the level where the lesion starts. However, unlike mammals, birds do not have a cauda equina, thereby making myelography less safe to perform without causing injury to the spinal cord.9 Some avian species, such as ducks, geese, and swans, also have overlapping plates of bones over the thoracic and lumbar vertebrae that would prevent a needle from being placed in the subarachnoid space.10 Birds also have a space in the lumbosacral portion of the spinal cord that contains the glycogen body, which consists of nerve fibers with possible roles in neurosecretion and regulating vascular reflexes.11 Another feature unique to birds is that the internal vertebral venous plexus extends down the entire vertebral column, connecting to the venous drainage of the kidney.12 This connection may be a route for infectious agents or tumor cells to travel between the vertebral column and the rest of the body.
The low number of reported avian cases of diskospondylitis does not allow many conclusions to be made regarding common features of signalment among affected birds; both the affected penguins were female, the peregrine falcon was male, and the white stork was of unknown sex.1–4 There was also no common age pattern among the reported avian cases; the yellow-eyed penguin was 1 year old, the African black-footed penguin was 22 years old, the peregrine falcon was 6 weeks old, and the white stork was of unknown age.1–4
The case described in the present report highlighted the fact that a diagnosis of diskospondylitis can be made for birds through detailed anamnesis and findings of thorough physical examination (including neurologic examination) and advanced diagnostic imaging (eg, CT). Unfortunately, treatment of this greater flamingo was unsuccessful, and the bird was euthanized.
Footnotes
Metacam, Boehringer Ingelheim, Ridgefield, Conn.
Baytril, Bayer AG, Kaiser-Wilhelm-Allee, Leverkusen, Germany.
Baxter Healthcare Corp, Deerfield, Ill.
Sporanox Oral, Janssen-Ortho Inc, Toronto, ON, Canada.
Neurontin, Pfizer Inc, New York, NY.
Revolution ACT, GE Healthcare, Chicago, Ill.
Iso Flo, Abbot Laboratories, North Chicago, Ill.
Bactrim, F. Hoffmann-La Roche Ltd, Basel, Switzerland.
References
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2. Field CL, Beaufrère H, Wakamatsu N, et al. Discospondylitis caused by Staphylococcus aureus in an African black-footed penguin (Spheniscus demersus). J Avian Med Surg 2012;26:232–238.
3. Poeta P, Sargo RF, Valente JM, et al. Serratia marcescens discospondylitis in a white stork (Ciconia ciconia). SOJ Microbiol Infect Dis 2016;4:1–5.
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7. Braga JFV, Silva CC, Teixeira MPFT, et al. Vertebral osteomyelitis associated with single and mixed bacterial infection in broilers. Avian Pathol 2016;45:640–648.
8. LaCroix JA. Vertebral body osteomyelitis: a case report. Vet Radiol 1973;14:17–21.
9. Orosz SE, Bradshaw G. Avian neuroanatomy revisited: from clinical principles to avian cognition. Vet Clin North Am Exot Anim Pract 2007;10:775–802.
10. Platt S. Evaluating and treating the nervous system. In: Harrison GJ, Lightfoot T, eds. Clinical avian medicine. Palm Beach, Fla: Spix Pubishing, 2006;2:493–515.
11. Pessacq-Asenjo TP. The nerve endings of the glycogen body of embryonic and adult avian spinal cord: on the existence of two different varieties of nerve fibers. Growth 1984;48:385–390.
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