Answer to Case 485

Answer: Angiostrongylus cantonensis,  the rat lungworm

As many of you mentioned, the clues to the identification of this parasite are the characteristic morphology of the larvae, the host (snail), and the predilection of the parasite for the human central nervous system (CNS). A. cantonensis can infect snails and slugs, which if accidentally ingested, can lead to debilitating, even fatal, eosinophilic meningitis in humans when the immature worms migrate to the CNS and die. Human infection can also be acquired through ingestion of infected paratenic hosts such as crabs and fresh water shrimp, and may potentially be acquired through ingestion slug/snail slime containing L3 larvae on inadequately-washed vegetables.

Although this infection was first identified in Asia, it has spread throughout the Pacific basin, and is also found in parts of Africa, the Caribbean, and Ecuador. Florida Fan points out that the related organism, A. costaricensis, causes intestinal angiostrongyliasis, and is found in parts of South and Central America. Most cases of A. costaricensis infection are reported from Costa Rica

Here are some nicely-labelled images that Dr.  Solórzano Álava created for this case that demonstrate the key morphologic features. I find the pointed tail to be especially helpful!