Naegleria

see also:

• parasites
• http://www.cdc.gov/parasites/naegleria/pathogen.html
• MJA 2016 article: Primary amoebic meningoencephalitis in North Queensland

• Naegleria fowleri is an aerobic amoeba which lives in waters at temperatures above 25degC (eg. thermal springs) and can cause rare fatal encephalitis (primary meningoencephalitis (PAM) ) if the 10-35 micron trophozoites gain access to nasal mucosa of humans - such as with playing, swimming, underwater diving in such waters, or people who do sinus washouts with contaminated water.
• trophozoites optimum temperature is 46degC but can survive at temperatures up to 65deg C for several hours
• trophozoites can turn into a temporary, non-feeding, flagellated stage (10-16 µm in length) when stimulated by adverse environmental changes such as a reduced food source
• if the environment is not conducive to continued feeding and growth (like cold temperatures, food becomes scarce) the amoeba or flagellate will form a cyst. The cyst form is spherical and about 7-15 µm in diameter
• cysts become nonviable within 5 minutes of being dried but can survive near-freezing conditions
• trophozoites and the more resistant cysts are sensitive to disinfectants like chlorine

• exposure to warm waters contaminated with Naegleria fowlerii such as thermal springs or untreated bore water in tropical regions
• incubation period 2-15 days
• fevers, rhinorrhoea, vomiting over 1-2 days which progress to features of bacterial meningitis such as:
  • lethargy
  • irritability
  • meningism
  • possible maculopapular rash
  • raised intracranial pressure:
    • possible seizures
    • increasing drowsiness and decreased GCS which may progress to death within hours
• mortality rate of over 97% once symptoms start, with death typically arriving within two weeks after exposure

• clinical evidence of meningitis with history of exposure
• lumbar puncture CSF microscopy showing motile trophozoites on a wet preparation and Giemsa stain and confirmed with CSF PCR
• NB. CSF chemistry is similar to bacterial meningitis CSF

• supportive care in resuscitation area with aim for transfer to ICU
• iv access
• initial empirical antibiotics as for basterial meningitis
• initial anitivirals for possible herpetic encephalitis
• if possible Naegleria from exposure history, it would appear that early combination antifungal Rx which has access to CNS is required to reduce risk of death ¹⁾:
  • intrathecal amphotericin
  • miltefosine, fluconazole and rifampicin
• CT scan
• lumbar puncture