Rat lungworm (Angiostrongylus cantonensis) is a parasitic nematode that is the most common cause of eosinophilic meningitis (meningitis with a high percentage of eosinophils in the cerebrospinal fluid). There have been 12 recorded cases of rat lungworm in recent years, including toddlers. While infection from rat lungworm is not fatal and often resolves on its own, severe infection can result in long term neurological damage.
The life cycle of rat lungworms begins with rats, as the name suggests. The nematodes infest the rat’s digestive system when they are ingested, then spread to the lungs, kidneys, and brain. Nematodes reach full maturity within the rat and reproduce in the respiratory tract, where their eggs are laid and hatched. First-instar migrate to the trachea, and then pass into the rat’s feces.
Snails and slugs consume the nematodes from the rat feces. Nematodes will molt to second and third instar larvae while in the mollusc, but will not reproduce. They are able to remain relatively inactive in the molluscs until a rat feeds on the mollusc and ingests the nematodes, thus completing its life cycle.
Humans contact rat lungworm when they touch or eat the infected molluscs. Gardeners who deal with mollusc pests are the most likely to contract rat lungworm, either by handling the molluscs without gloves, or by accidentally eating a snail/slug from their fresh vegetables. Toddlers may also eat snails or rat feces if they swallow dirt.
The best way to avoid rat lungworm infection is not to consume raw or undercooked terrestrial molluscs. No one should never handle snail or slug pests with their bare hands. If mollusc infestations are severe in the garden, you can also soak vegetables in a mild (1.5%) bleach solution to disinfect them.
Learn more about rat lungworm in this EDIS publication by John Capinera and Heather S. Walden.