Abstract The parasitic nematode Angiostrongylus cantonensisis the leading cause of neuroangiostrongyliasis, is an emerging tropical disease, and is the leading cause of eosinophilic meningitis worldwide. Diagnosis is generally presumptive and can be easily confused with other central nervous system disorders. Several studies have demonstrated the promise of immunodiagnosis, most frequently in the form of ELISA assays. Taking advantage of plasma samples from previous rat studies, we developed an indirect ELISA assay based on the 31 kDa antigen isolated from A. cantonensiscollected in Hawai’i. Using IgG, our assay showed 100% sensitivity, and specificity in diagnosing A. cantonensisinfection in lab-reared rats fed 50 live larvae six weeks previously. We saw diminishing sensitivity to IgM, IgA, and IgE, respectively, and no antibody response in rats fed killed A. cantonensislarvae. Our experiments validate the use of indirect ELISA with 31 kDa antigen as an effective immunodiagnostic assay for rats, and our use of different antibody isotypes provided an opportunity to investigate in more detail the humoral immune response in lab-reared rats to A. cantonensisinfection. Daniel K. Inouye College of Pharmacy, Hawaii State Legislature