Angiostrongylus cantonensis, also known as rat lungworm, is a parasite that can infect humans when they consume undercooked or raw snails, slugs, or other animals. The worm larvae can invade the central nervous system and cause eosinophilic meningitis. To diagnose rat lungworm infection, IgM and IgG tests are used to detect antibodies against this parasite. IgM test: This test detects IgM antibodies, a type of antibody that usually appears early after infection. A positive IgM result may indicate a recent or active infection.