Rat Lungworm Backwash: Why Slugs are Not the Best Drinking Partners

One of the latest obscure and tantalizing infectious diseases to garner sensationalistic headlines is "rat lungworm disease" in Hawaii.

This infection, caused by the roundworm Angiostrongylus cantonesis, is not a very common entity in the US though outbreaks and sporadic infections occur worldwide. In its natural infective cycle, this worm is ingested by rats via mollusk intermediaries such as snails, prawns, and slugs. The larvae migrate through the vasculature to the lungs and to the brain. Adult parasites live in the lung and lay eggs which, after hatching, are coughed up, swallowed, and passed into the feces to find a mollusk host and the cycle repeats. 

When humans get caught up in the cycle after, for example, ingesting an uncooked snail or a salad contaminated by larvae the result is eosinophilic meningitis arising from larval migration to the brain. This condition is usually just a mild illness but can lead to coma and death with massive infections. Fever, nausea, vomiting, and neck stiffness are common symptoms. It is diagnosed clinically and through spinal tap where a larvae may be spotted in the cerebrospinal fluid. Treatment is usually with steroids. 

This year 11 cases have been reported on two of Hawaii's islands and represents an increase over the expected number of cases which usually number about this many for the entire year. Speculation is that an influx of semislugs on Maui may be responsible for this increase as at least 2 cases arose from a homemade kava elixir which they shared with slugs. 

I suspect that this outbreak will be contained once public awareness rises and people are more careful of their exposure to foods that might harbor the parasite and take appropriate action like cooking it, washing it, and discarding it if slugs have decided to have a bite or drink too. 

A general rule of thumb, however, is not to share straws with a slug.