Tips for dealing with rat lungworm

Photo caption: Semi-slugs, shown on left, are effective carriers of rat lungworm disease, as are the much larger Cuban slugs. Courtesy of Hawaii Department of Health.

Rat lunworm disease — spread in Hawaii by introduced pests — is the latest scourge that Hawaii farmers are currently facing. Cases have been reported from Hawaii Island and Maui, but the other islands are also vulnerable.

Media reports indicate that some consumers are starting to shun Island produce, especially greens, although rat lungworm has also been reported in Alabama, California, Louisiana and Florida, and is prevalent in parts of Asia, other Pacific islands and the Caribbean.

While some of this is a public perception problem, there are steps that farmers can take to reassure consumers and minimize the likelihood that their own crops will be impacted.

The scientific name for rat lungworm disease is Angiostrongyliasis. It’s caused by Angiostrongylus cantonensis, a parasitic nematode (roundworm) that is found in rodents, particularly rats. Rodents expel the worm’s larvae in their feces, which are then ingested by snails, slugs, crabs and frogs. Snails and semi-slugs are common intermediary hosts, giving the larvae a place to grow until they are infective.

The larvae travel to the central nervous system, where they can cause eosinophilic meningitis, a serious condition that can lead to permanent brain and nerve damage, and even death. Symptoms include mild to severe headache, fever, stiff neck, tingling or painful feelings in skin or extremities, and temporary paralysis.

While the parasites are prevalent in Southeast Asia and tropical Pacific islands, the disease is still relatively rare in humans. Most people completely recover without treatment, according to the U.S. Centers for Disease Control and Prevention.

The most likely source of transmission to humans appears to be through the consumption of raw snails and tiny young semi-slugs, which can hide in leafy greens or cling to other vegetables and fruit.

As farmers, there are measures you can take to help control and prevent the spread of this disease, protect yourself and reassure your customers. Here are some examples:

• Strive to have your fields, packing areas and home gardens free of rodents, snails and slugs, as rats are the primary carrier of the parasite.

• Train your workers to alert you of the presence of rodents, snails and slugs in the field, during harvest, in packing sheds, etc.

• Document your management activities; e.g. where traps and baits are placed, which ones had rodents/slugs/snails. (Successful trapping should guide where you bait). This documentation can be used to show your customers the preventative measures you are taking.

• Communicate with your customers about the specific practices and steps
you take to provide healthy products. They want assurance that care has been taken in growing them.

• Those selling or sharing plants, flowers, nursery products that may provide a hiding place for slugs and snails should inspect the products before they leave your property.

General tips for homeowners and consumers:
• First wash your hands, then carefully and thoroughly wash all produce, especially leafy greens like kale that have folds that make it hard to see and detect tiny slugs and snails.
• Protect cleaned produce from pests and make sure your prep areas and utensils are clean. Slugs can easily climb onto tables when cooking outdoors.
• Freshwater prawns, shrimp, crabs, mollusks and frogs can also be carriers of the parasite so do not eat these raw. Cooking destroys the parasite, but make sure you cook them to an internal temperature of 165 degrees.
• Pets (especially dogs) also need to be protected. Check food and water bowls regularly for slugs. Do NOT leave uncovered bowls of food outside overnight.

Locally grown produce is safe to eat as long as the proper care precautions outlined above are taken, no matter where the food comes from, says Anna Koethe
, spokeswoman for DOH.

Please see the previous HFB blog post for links to specific information on all aspects of this issue.

The Hawaii Department of Health has more information here.

The University of Hawaii, College of Tropical Agriculture and Human Resources website also has detailed information.