Pathways for transmission of angiostrongyliasis and the risk of disease associated with them

Abstract

Angiostrongylus cantonensis, the rat lungworm, is a major cause of eosinophilic meningitis in humans. This short paper reviews what is known about the pathways of infection and assesses the probable importance of each in causing disease. Rats are the definitive hosts. People can become infected by eating, both deliberately and inadvertently, raw or under-cooked intermediate hosts (snails or slugs) or paratenic hosts such as freshwater shrimp, crabs and frogs. Food preparation prior to cooking can leave debris from which infection can also occur. It may be possible to become infected by consuming snail/slug slime (mucus) on produce or by transferring mucus from hands to mouth after handling snails/slugs. Infection from consuming drinking water contaminated by snails/slugs and infection via open wounds may be theoretically possible but no cases have been reported. The severity of the disease is probably related to the number of infective larvae ingested as well as to the precise location of the worms in the host and the host's inflammatory response. Strategies for reducing human infection should include snail and slug control to reduce chances of accidental ingestion, cooking of intermediate and paratenic hosts, and public education on food preparation.

Keywords: Angiostrongyliasis; Angiostrongylus cantonensis; Emerging infectious disease; Eosinophilic meningitis; Parasitology; Rat lungworm disease; Slugs; Snails.

Figure 1

Two important intermediate hosts of Angiostrongylus cantonensis: left - the giant African snail, Achatina fulica (photo R.H. Cowie); right - an apple snail, Pomacea canaliculata (photo K.A. Hayes); both photographed in Hawai‘i where they are invasive alien species. Scale bars approximately 2 cm.