Rat lungworm is an infection caused by a parasitic roundworm (Angiostrongylus cantonensis) that infects rats. The larvae or immature form of the parasite are passed in the feces of infected rats and consumed by snails, slugs and other animals. The parasite matures and reaches an infective stage within the snails and slugs.

Rats get infected when they consume an infected slug or snail. The parasite larvae mature into adults in the rat and then lay their eggs. These eggs hatch and begin the cycle anew when they are excreted in the rat droppings.

Humans can become infected by ingestion of the parasite by eating raw or undercooked infected animals such as snails, slugs and freshwater prawns, or by consumption of raw produce contaminated with parasitic larvae.

To minimize your risk of rat lungworm disease in your garden, it is important to control and exclude all hosts of the parasite — rats, snails and slugs.

HIDING SPOTS

Rats, snails and slugs thrive where there is ample debris and litter for them to nest or hide in. Eliminating food, water and climbing/shelter sources for these pests around your home will make it more difficult for these pest populations to grow.

Clean gutters and catchment tanks, and remove debris or rotting materials, such as wood and rock piles. Clear away old flowerpots and plastic mulch and trim vegetation away from walls, windows and roofs to reduce the chance of snails, slugs and rats from entering the home.

Pick up fallen and rotting fruit in your yard and surrounding areas so it does not become food for rats, slugs and snails.

Dry up water sources. Slugs and snails are nocturnal and prefer moist environments. Avoid watering late in the day and instead water plants in the morning to allow time for excess water to dry.

Store pet food in pest-proof containers, and do not leave pet food dishes outside overnight. Snails and slugs are attracted to pet food, and the rat lungworm parasite can sicken pets if accidentally ingested.

TRAPS AND CHOPSTICKS

To repel pests, barriers such as broad metal bands around tree trunks can prevent rats from climbing. Snails and slugs are deterred from crossing into areas by 2- to 4-inch copper bands.

Trapping, if done regularly, is very effective for controlling rats. Rats tend to be cautious, so for best results, place unset traps in an area for a few days before setting them in areas where children and pets won’t be hurt.

Physical removal of snails and slugs can be an effective control measure. Use gloves and disposable chopsticks or designated tongs to pick up snails and slugs. Place pests in a solution of 7 parts water to 1 part salt and let sit for at least 48 hours to kill slugs, snails and parasites.

Baiting for rats, snails and slugs can be very effective in reducing pest populations. Caution should be exercised with any pesticide use, and safety should be a primary consideration. It is a violation of federal law to use a pesticide in a manner inconsistent with the directions. Read the label carefully.

For rats, it is best to use tamper-proof bait stations that only the rat can encounter because rat bait can be harmful to children, pets and other wildlife.

SLUG AND SNAIL BAITS

For slug and snail control, there are several bait formulations. For home garden use, use baits whose active ingredient is relatively safe to use around children and pets, such as iron phosphate. Baiting is most effective when placed during late afternoon or evening. Place bait in moist and protected locations and in known snail and slug crossings. Wet the area before applying bait to encourage snail and slug activity. Do not pile bait in mounds or clumps, especially more hazardous bait, because that makes it more attractive to pets and children.

When harvesting produce from your garden, pay close attention to your fruits and vegetables for food safety risks. Do not consume crops near feces or with physical damage caused by pests, which can expose your food to potential contamination.

PREVENTION TIPS

Whether your produce comes from your garden, Hawaii, the mainland or another country, all of it should be rinsed properly. Following these steps in the kitchen will reduce your risk of rat lungworm and other foodborne illnesses:

>> Wash your hands with soap and water.

>> Clean kitchen surfaces including countertops, cutting boards, knives and utensils, and other surfaces that might come in contact with your produce.

>> Separate leaves and sections of your fruits and vegetables.

>> Inspect your produce for dirt, debris and pests.

>> Rinse under clean running water. Create friction with your fingers or use a produce brush. Additives such as produce washes and vinegar do not reduce the risk of rat lungworm disease.

>> After proper rinsing, you can also cook fruits and vegetables to an internal temperature of 165 degrees.

Cynthia Nazario-Leary is a University of Hawaii Urban Horticulture Extension Agent and Kylie Wong is a University of Hawaii Sustainable Agriculture Extension Agent.