What is the treatment for amoebic meningitis?

Treatment of Amoebic Meningitis

The treatment of amoebic meningitis (Primary Amoebic Meningoencephalitis or PAM) should include a multi-drug regimen with miltefosine as a core component, as this has been associated with improved survival outcomes in this otherwise highly fatal disease. 1

Pathogen and Clinical Considerations

• Primary amoebic meningoencephalitis (PAM) is caused by Naegleria fowleri, a free-living amoeba found in warm freshwater environments, with mortality exceeding 95% 1
• The clinical presentation mimics bacterial meningitis but does not respond to standard bacterial meningitis antibiotics, making rapid identification critical 1
• Diagnosis is confirmed in only 27% of cases pre-mortem, highlighting the importance of considering this diagnosis in patients with meningitis symptoms and freshwater exposure 1, 2

Treatment Protocol

• First-line treatment regimen:

  • Miltefosine has shown improved survival outcomes when included in treatment regimens 1, 3
  • Amphotericin B administered via multiple routes (intravenous, intrathecal, and when possible, intraventricular) is a critical component of therapy 4, 5
  • Rifampicin should be added to the regimen as part of combination therapy 4, 5
  • Ornidazole has been used successfully in at least one reported survival case 4

• Treatment timing:

  • Immediate initiation of therapy is essential as death typically occurs within 5 days of presentation if treatment is unsuccessful 1
  • Early treatment with amphotericin B and rifampicin may improve survival chances 4

Diagnostic Approach

• In cases of suspected meningitis where CSF staining, antigen detection, or culture is negative for bacteria, a wet mount cytology of CSF should be performed to look for Naegleria 4
• Consider PAM in any patient with meningitis symptoms who has participated in outdoor water activities or practices nasal rinsing 2

Risk Factors and Prevention

• Exposure to warm freshwater bodies, especially during summer months 1
• Nasal irrigation with contaminated water, ritual nasal ablution, and lawn water slides have been implicated in cases 1
• Cases are being reported in northern regions where they were previously not present, potentially related to climate change 1, 2
• Prevention includes avoiding swimming in warm freshwater and preventing nasal exposure during water activities in potentially contaminated water 1

Common Pitfalls to Avoid

• Misdiagnosing as bacterial meningitis and failing to consider amoebic etiology in patients with freshwater exposure 1, 2
• Delaying treatment while waiting for confirmatory diagnosis, as the disease progresses rapidly 1, 6
• Using only standard bacterial meningitis antibiotics without specific anti-amoebic agents 1
• Failing to administer amphotericin B through multiple routes (IV, intrathecal, intraventricular when possible) 5

Prognosis

• Despite treatment, prognosis remains extremely poor with mortality >95% 1
• A few survival cases have been documented with early diagnosis and aggressive multi-drug therapy including miltefosine, amphotericin B, and rifampicin 1, 4, 3