Answer: Eosinophilic meningitis due to Angiostrongylus cantonensis
All the respondents did a great job on getting the correct answer on this challenging case.
As nicely stated by B.A.M, the identification can be made by the presence of a "syncytial, nucleated intestine, lateral chords (a bit flat in this case), smooth, thin cuticle, polymyarian musculature, and lack of alae (seen in Toxocara). Looks like an immature female, non-gravid reproductive tube present. This species rarely develops to sexual maturity in the human host."
Also in the differential is Gnathostoma species, which would be differentiated from Angiostrongylus cantonensis by its distinct morphologic features, including voluminous lateral cords.
In these cases, it is very helpful to have a travel and exposure history. However, as MicrobeMan said, "Perhaps the patient does have history of travel that we just don't know about." In this case, no further history was available.
Vspyder points out that "A. cantonensis is the most common cause of eosinophilic menhingitis in asia and the south pacific" while Matthew Rollosson mentions that this parasite has also been found in Australia, some areas of Africa, the Caribbean, Hawaii and Louisiana. See the CDC general information site and DPDx web site for more details.
Thanks to all of my readers for their comments!