Semi-Slug Found in Kohala Sparks Rat Lungworm Vigilance

A collection of Parmarion martensi, an invasive semi-slug, has been confirmed in the Kohala district of the Big Island by staff from the University of Hawaiʻi-Hilo Daniel K. Inouye College of Pharmacy. Inquiries of local residents further revealed multiple sightings in the area, indicating that this invasive pest has established in the Kohala district of the Big Island, according to information compiled by the Big Island Invasive Species Committee.

Semi-slug captured in Kohala by students. PC: Big Island Invasive Species Committee

Commonly called the “semi-slug” for the partially formed shell on its back, the semi-slug has been associated with increased incidences of Angiostrongylus or rat-lungworm disease, according to the BIISC. The parasite, Angiostrongylus cantonensis, infects rats and snails or slugs at different times during its life cycle.

Humans can contract the disease after accidentally consuming the parasite from a slug or snail. Cases range from severe discomfort and illness to permanent disability, or even death, depending on the amount of microscopic parasites consumed. Although all snails and slugs can carry the infective form of the parasite, semi-slugs are known to be carriers of a much heavier load of parasites, according to the BIISC.

The presence of the slug was confirmed through the efforts of students at Kohala Middle School, who are participating in a citizen science effort led by teacher Cristy Athan. Athan enrolled in a professional development class offered by UHH-DKICP and the Big Island Invasive Species Committee to learn more about rat lungworm and invasive rats and slugs.

Teachers are taught safe handling protocols for the collection and disposal of snails and slugs, and are guided to develop an Integrated Pest Management Strategy to reduce slug and snail populations in school gardens.

Kay Howe instructing teachers on slug identification during a teacher professional development session held at Waimea Middle School in Nov 2018. PC: Big Island Invasive Species Committee

“They’re so into it,” said Athan of students who have embraced the project, “enthusiastically committed to their roles as ambassadors for rat lungworm prevention.”

Kay Howe, DKICP education coordinator at UHH, was inspired to create the curriculum after her son contracted a serious case of the disease in 2008. Although she had worked at a school garden in Waimea the year before, she had never heard of rat lungworm disease.

“I was concerned because my mind kept coming back to that school garden. As school gardens were being put in at schools across the island I was so excited for the opportunity for the students to learn about agriculture and growing their own nutritious food, but I also worried – what are they doing about rat lungworm? Do they even understand the risk?”

Residents of Kohala are asked to be vigilant for this slug and to be extremely careful with washing garden vegetables.

Slugs or snails should never be collected with bare hands – gloves or chopsticks can be used to dispose of slugs in heavily salted water. Slug bait can reduce populations around gardens and yards. Resources on RLW and on the teacher training can be found at www.biisc.org.