Treatment for Naegleria fowleri Infection (Primary Amoebic Meningoencephalitis)
The recommended treatment for Naegleria fowleri infection is aggressive combination therapy including intravenous AND intrathecal amphotericin B, along with miltefosine, and additional agents such as azithromycin, rifampin, or miconazole. 1
Clinical Presentation and Diagnosis
Primary Amoebic Meningoencephalitis (PAM) caused by Naegleria fowleri presents with:
Early symptoms (2-5 days post-exposure):
- Change in taste/smell
- Headache
- Fever
- Nasal congestion
- Vomiting
Late symptoms (3-4 days after initial symptoms):
- Stiff neck
- Confusion
- Abnormal behavior
- Meningismus
- Papilledema
- Nystagmus
- Cranial nerve abnormalities
- Ataxia
Diagnosis requires:
- CSF analysis showing neutrophilic pleocytosis and low glucose
- Direct microscopy of CSF to identify motile trophozoites (cornerstone of diagnosis)
- PCR testing from CSF or tissue (available from CDC)
- MRI may show frontal lobe involvement
Treatment Protocol
First-Line Therapy
Amphotericin B:
- Administer both intravenously AND intrathecally 1
- Intrathecal administration is essential to reach effective concentrations in CSF
- Monitor renal function closely due to nephrotoxicity
- Monitor cardiac function, especially if hypokalemia develops
Miltefosine:
- Now commercially available in the USA
- Critical component of combination therapy
Additional Agents (as part of CDC-recommended combination therapy):
- Rifampin
- Azithromycin
- Sulfisoxazole or miconazole
Treatment Considerations
- Early initiation of therapy is critical - do not wait for confirmed diagnosis as this disease progresses rapidly
- Mortality exceeds 95% without prompt treatment 1
- Recent treatment advances using combination therapy including miltefosine have improved survival rates
- Amphotericin B is not FDA-approved specifically for PAM but is used off-label for this life-threatening infection 2
Epidemiology and Risk Factors
- Most cases occur after exposure to warm freshwater bodies during summer months
- Historically concentrated in southern US states but now reported in northern regions
- Alternative transmission routes include:
- Municipal water supplies
- Sinus irrigation with contaminated water
- Ritual nasal ablution
- Water slides
Prevention Strategies
- Avoid swimming in warm freshwater during periods of high water temperature and low water levels
- Use nose clips or avoid submerging the head when swimming in freshwater
- Maintain minimum chlorine residual (15 ppm) in water systems
- Use filtration through 0.1-0.2 μm filters
- Properly disinfect pools, water slides, and recreational water facilities
- Avoid using untreated tap water for nasal irrigation or sinus rinsing
Pitfalls and Caveats
- PAM is often misdiagnosed as bacterial meningitis due to similar presentation
- Delayed diagnosis significantly reduces survival chances
- Only about 27% of cases are diagnosed pre-mortem 1
- Treatment must begin empirically if PAM is suspected - waiting for confirmation is often fatal
- The disease progresses extremely rapidly, with death typically occurring within 5 days of presentation due to cerebral edema
- Even with aggressive treatment, mortality remains extremely high
Monitoring During Treatment
- Monitor intracranial pressure
- Assess renal function daily due to amphotericin B nephrotoxicity
- Monitor electrolytes, particularly potassium levels
- Perform serial neurological examinations
- Consider repeat CSF analysis to assess treatment response
Early recognition, rapid diagnosis, and immediate initiation of aggressive combination therapy represent the only chance for survival in this devastating infection.