What's interesting is that a 1986 study found that a flubendazole-mebendazole 7-to-10-day treatment killed in the range of 93-99% of rat lungworm larvae (this study was in rats).  So we have longstanding study data to back up experience in human use. Neither drug has common side effects beyond gastric distress in p.o. usage, and serious side effects are uncommon.  Obviously the prescribing MD would need to assess the patient for allergy potential, but in general the contraindications would be few.

We also need to consider the best "rough and ready" diagnostic tool.  In fact that's almost trivial.  A small but significant number (or percentage) of eosinophils in the CSF is diagnostic of eosinophilic meningitis.  The vast majority of these cases are caused by rat lungworm.  Therefore a simple CSF differential would be a sufficient first cut to pop rat lungworm to the top of the Dx differential or basically rule out an acute infestation.

These tests and treatments are straightforward.