Case of the Week 229

A child presented with rapid onset of headache, confusion, and mental status changes after spending the weekend swimming in a warm fresh water lake.  A lumbar puncture was performed and the following structures were seen in a Giemsa-stained cytospin preparation of CSF (CLICK ON IMAGES TO ENLARGE):

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Unfortunately, the child quickly became obtunded and was declared brain dead within 24 hours of presentation.  An autopsy was performed, which showed the following:

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Diagnosis for this tragic case?