When parasites and invasive species interact with other creatures, the combination can be deadly. This is the case in Hawaii, where a parasite inside infected snails or slugs can lead to brain damage or even death in humans. This typically happens when people consume water or food contaminated by the snails or slugs or, to a lesser degree, their slime.
Yet, as was demonstrated during the COVID-19 pandemic, GIS technology can track disease outbreaks and help limit disease spread by informing the public with visualized spatial data. This is why a group of educators, scientists, and GIS technicians are using ArcGIS Online and ArcGIS Survey123 to gather data and help educate schoolchildren in Hawaii about the condition, known as rat lungworm disease.
Rats, Slugs, Roundworms, and People
Rat lungworm disease is caused by rat lungworms, which are native to Southeast Asia but were first discovered in Hawaii in 1959. These creatures require two different hosts to complete their life cycle: rats and either slugs or snails. Rats excrete newly hatched rat lungworm larvae in their feces, which the snails and slugs consume. The larvae then grow into infectious-stage larvae. When an infected slug or snail is then eaten by a rat, the larvae continue to grow and develop into young adults in the rat’s brain, eventually breeding and then laying eggs in the rat’s pulmonary artery and lungs.
This cycle poses little risk to the rats, slugs, or snails. But humans, dogs, horses, and other creatures can also become infected, usually by consuming unwashed produce or drinking water that has been contaminated by infected slugs and snails. After infection from contact with the slug or snail, the parasite—like in the rat—targets the host’s brain and central nervous system, often leading to health issues due to inflammation and swelling of the membranes in the brain and spinal cord.
In the state of Hawaii, from around 2005 to 2007, there was a rise in such cases, mostly on the island of Hawaii, the largest island in the state. For example, the US Centers for Disease Control and Prevention calculated an average of 7.4 cases per 100,000 people each year on the island of Hawaii from November 2004 to February 2005, versus just 1.1 from January 2001 to October 2004. Many of the infections were serious, with some resulting in coma, long-term hospitalization, disability, and even death.
This increase corresponded with the arrival in Hawaii of an invasive species called the semi-slug. This part-snail, part-slug creature looks like a slug, but it has an unusual characteristic—a section of shell that covers a small portion of the creature, much like how a fingernail covers part of a finger. Native to some tropical areas in Asia, semi-slugs carry much higher parasite loads than other species, so they are more likely to cause infection when consumed.
Researchers eventually determined that accidental hosts, such as humans and other animals, were likely contracting rat lungworm disease following contact with slugs and snails or, potentially, their slime. Specifically, it was showing up in people who ate produce that was not thoroughly washed and that had been grown in gardens where snails or slugs had been seen.
Raising Awareness of the Disease
Hawaii’s state government advocates for consumption of fresh, locally grown produce, as people in this remote island chain rely heavily on imported food. This has increased the number of home and school gardens, which raises the risk of contracting rat lungworm disease. But school garden programs also provide an opportunity to raise awareness of the disease among teachers and students—and, by extension, their families.
The State of Hawaii made the disease reportable in 2007. In 2012, after five years of increasing confirmed cases—and undoubtedly other, undiagnosed cases, since confirmation requires a spinal tap—staff at the University of Hawaii at Hilo Daniel K. Inouye College of Pharmacy’s Jarvi Lab began conducting research and developing educational outreach materials related to rat lungworms. By 2013, Jarvi Lab education specialists had created an activity book for young children and began leading classes at five public schools that had gardens. In 2017, the specialists completed a curriculum for Hawaii students from age five through high school that was focused on rat lungworms as well as a management plan for controlling slugs and snails in school gardens. The researchers also created an ArcGIS StoryMaps story and a paper about the project. By 2022, dozens of schools in Hawaii were using the teaching materials, reaching hundreds of students.
Professional GIS Development for Hawaii Teachers
The Jarvi Lab then partnered with the Big Island Invasive Species Committee, the Hawaii Farm to School Hui, the Hawaii Public Health Institute, and Iolani School to create a professional development education course for Hawaii teachers. The online course relies heavily on research-driven lessons that focus on rat lungworm disease, prevention strategies, and the pest management plan. This approach engages teachers and students as community educators and citizen scientists.
Teachers who take the course gain continuing education credits while acquiring and sharpening their skills in place-based education; science, technology, engineering, art/agriculture, and math instruction; design thinking; citizen science; and community engagement.
Along the way, these teachers learn how to use ArcGIS Online for various course projects as well as career advancement and professional development. They also created a StoryMaps story to show how Hawaiian children are learning about the disease and how to prevent it.
A Research App for Locating Slugs and Snails
Semi-slugs have been confirmed on the islands of Oahu, Hawaii, and Maui, but their presence has yet to be fully mapped. It is unknown whether semi-slugs have arrived on other Hawaiian islands or if they live at higher elevations—a key issue for cool-weather crops such as lettuces.
To help gather this data, Big Island Invasive Species Committee members created a slug/snail mobile reporting app in Survey123. Teachers and students tested the app in a recent professional development education course. Survey results appear in Map Viewer and on dashboards created with ArcGIS Dashboards.
The reporting app is expected to be available to the public by early 2025. In an upcoming webinar, experts from the partnership will introduce the app and discuss best management practices and safety measures for controlling potentially infected slugs and snails.
With the app, teachers and students—along with farmers, gardeners, and members of invasive-species committees across Hawaii—will work as citizen scientists, collecting photographs and mapping the locations of slugs and snails. These researchers, who will be watching for semi-slugs in particular, will provide information that will show where different species are found and where to focus pest management efforts and disease-prevention education.
Next Step: High Schools
The next step in this educational effort is to develop a high school curriculum that uses ArcGIS Online as well as ArcGIS tools in the classroom. The subject will be rat lungworm disease, but—once educated—teachers and students will be able to use the software to address other issues, especially invasive species in Hawaii.
Overall, this educational effort has likely helped save lives while providing educators with new teaching tools and a better understanding of GIS technology. For their students, these projects are opening a new world of possibilities for continued education and future employment.
