Bacterial Meningitis in Dogs: 83% Survival and Favorable Long-Term Outcomes in a Multicenter Case Series

Clinical presentation, treatment, and outcome of 24 dogs with bacterial meningitis or meningoencephalitis without empyema (2010–2020)

Faye Rawson, Max Foreman, Thomas Mignan, Jack Galer, Anne Fraser, Abbe Crawford

Background

Bacterial meningitis (BM) and bacterial meningoencephalomyelitis (BMEM) are serious inflammatory diseases of the central nervous system associated with high morbidity and mortality in humans, but outcome data in dogs remain limited. Clinical presentation in dogs can be variable, and BM/BMEM may resemble other inflammatory CNS diseases such as steroid-responsive meningitis arteritis. The authors aimed to describe clinical features, diagnostic findings, treatment approaches, relapse frequency, and long-term neurological outcomes in dogs diagnosed with BM/BMEM without empyema.

Methods

This was a retrospective multicenter case series including 24 client-owned dogs diagnosed with BM or BMEM between January 2010 and August 2020 at five UK referral hospitals. Inclusion criteria were based on cerebrospinal fluid (CSF) cytology, culture results, and/or neutrophilic pleocytosis with clinical response to antibiotics. Dogs with imaging evidence of empyema or intracranial abscessation were excluded. Data collected included signalment, clinical signs, laboratory findings, imaging results, CSF analysis, bacteriology, treatment details, and follow-up outcomes.

Results

The median age was 4.2 years, with brachycephalic breeds overrepresented. Clinical signs were most often acute, and neurological deficits were present in 75% of dogs, commonly involving vestibular dysfunction. Pyrexia was infrequently documented. Otitis media/interna was identified as the suspected source of infection in 63% of cases. CSF analysis revealed marked neutrophilic pleocytosis in all dogs, with intracellular bacteria identified in 63%, while CSF cultures were positive in 38%. Twenty dogs (83%) survived to hospital discharge. Median duration of antibiotic therapy was 8 weeks, with shorter courses in surgically managed dogs. Relapse was uncommon, and residual neurological deficits were reported in 47% of dogs with long-term follow-up, typically mild and most often vestibular in nature.

Limitations

The study was retrospective with a small sample size, variable diagnostic and treatment protocols, and incomplete long-term follow-up for all cases. Inclusion of dogs without definitive bacterial isolation raises the possibility that some cases may have had noninfectious inflammatory etiologies. Owner-reported outcomes were subject to recall and reporting bias.

Conclusions

Dogs with BM/BMEM without empyema generally have a favorable prognosis when treated promptly with antibiotics, with most surviving to discharge and many achieving full recovery. Otitis media/interna was the most common infection source, and relapses were rare. Although mild residual neurological deficits were relatively common, overall long-term outcomes were good, supporting aggressive medical and, when indicated, surgical management of this condition.

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