Cause
Several infectious agents have been isolated from diskospondylitis cases in
animals including Staphylococcus intermedius, Brucella canis, Corynebacterium
spp, Streptococcal spp, Escherichia coli , Pasteurella spp, Nocardia-like
organisms and various fungal infections. Fungal infections are very rare in the
UK but is seen in other countries such as the USA. The bacterium Staphylococcus
intermedius is the most common isolate from cultures taken from dogs with
diskospondyitis. Sometimes the infection is secondary to a penetrating foreign
body, such as grass seeds.
The route by which the site becomes infected
varies. In many cases the infection spreads via the blood system.
Diskospondylitis may be secondary to infection at another site in the body, such
as dental disease, prostate or urinary tract infections.
The diagnosis is confirmed by X-rays which shows the characteristic changes
of a collapsed joint space with bone destruction in the end plates of both
adjacent vertebrae. This results in dark (radiolucent) areas (called lysis),
with a reactive white (radiodense) region of new bone (called sclerosis) next to
it. Often there is bridging spondylosis
between the vertebrae. These radiographic changes can be seen about 4-6 weeks
after the infection establishes itself in the disk space.
A special imaging
technique called scintigraphy is available in some specialist veterinary centres
and this can help a clinician to identify the disease at an earlier stage than
conventional X-rays.
Treatment
Accurate treatment may necessitate the identification of the organism causing
the infection by culturing blood, or culturing samples aspirated or taken by
biopsy directly from the infected site. About 75% of cases are reported to have
positive blood cultures so invasive procedures should not be necessary in the
majority of cases. Brucellosis should be screened for by blood test and titres
over 1:250 are considered significant and represent bacteraemia, whereas lower
titres reflect previous exposure to the organism.
Following culture and sensitivity the most appropriate bactericidal
antibiotic is used and may need to be given for at least 4-6 weeks. Affected
animals should be rested with minimal exercise during this period.
If a foreign body is present this has to be removed surgically or the
infection will probably recur despite appropriate antibiotic therapy.
Sometimes surgical curettage is needed at the site to remove chronically
infected tissue and facilitate local administration of anti-infective agents.