Thursday, May 11, 2017

The Big Lie: You're safe from rat lungworm on O`ahu and Kaua`i. You're not. People getting sick everywhere.

You might read media reports and believe rat lungworm disease or angiostrongyliasis is restricted to one, two or no more than three Hawaiian islands—and that you’re safe for now eating fresh veggies on other islands.

That’s wrong—potentially dead wrong.

This is a pretty rare, but a very spooky disease, and if you read or listen to most media reports, you'd feel safe in thinking the danger is at the eastern end of the Hawaiian chain. That's false.

Media reports notwithstanding, rat lungworm disease has impacted humans on all six of the major islands, and the disease vector has been found on five of the Hawaiian islands.

The painful and sometimes fatal disease, for which there is no treatment, has been identified on Hawai`i and Maui, but also on O`ahu, Kaua`i and Molokai—thus far no confirmed reports have come from Lana`i and Ni`ihau.

The very first reported Hawai`i case of rat lungworm disease, caused by the organism known to science as Angiostrongylus cantonensis, was in 1960, not on Maui or the Big Island, but in a man in Honolulu on O`ahu.
  
University of Hawai`i student Jaynee Kim in 2013 conducted a statewide study for a master’s thesis and found the disease in slugs and snails across Hawai`i. 

“Numerous gastropod species (16 of 37 screened) tested positive for A. cantonensis, with a large range of parasite load among and within species. The parasite occurs on five of the six largest islands (not Lanai),” Kim wrote.

And people have gotten sick all across the state: “There have been cases on all six of the largest Hawaiian Islands (Kauai, Oahu, Maui, Molokai, Lanai and Hawaii), with a noticeable increase in the number of cases since around 2004,” Kim wrote.

How is it that someone on Lanai got sick even though the nematode has not been found there? Said Kim “It is possible that produce regularly shipped from Maui was contaminated and the victim was infected through consumption of such produce, or that the victim became infected while on another island.”

Rat lungworm disease is caused by a parasitic nematode whose life cycle goes through rats and slugs, and can be caught by humans who eat the slugs or nematode larvae in slime trails on fruits and vegetables. The worms migrate to the human brain, where they mature, die and can cause a massive reaction, described by medicine as eosinophilic meningitis.

Live snails can carry large numbers of rat lungworms, but even the snail slime trails can carry small amounts. Here is a UH-Hilo report on the infectiousness of snail slime. 

“The larvae die when they reach the central nervous system, primarily in the brain, which can lead to eosinophilic meningitis. In humans, the resulting symptoms include nausea and headache, and in more severe cases, neurologic dysfunction, coma, and death,” wrote the authors of this paper

The slugs can be tiny, and can be easy to miss on improperly washed food. Giant African snails, which are common pests in yards and gardens throughout the Islands, can also be carriers. So can lots of other garden slugs and snails. The species most commonly linked to the disease is the semislug, Parmarion martensi.

The state Department of Health today (Thursday May 11, 2017) reported a new case on Hawai`i Island, bringing to 15 the number of recent cases. But while the most recent cases of people getting sick have all been on Maui and Hawai`i Island, there have been earlier cases of human illness from each of the other islands as well, starting with the 1960 O`ahu case. Only Ni`ihau has been spared.

Rat lungworm cases have been an annual occurrence in the Islands for more than the last decade. (The Department of Health reported 2 cases in 2007, 8 in 2008, 6 in 2009, 9 in 2010, 7 in 2011 and so on, according to this report.) 

This doesn't mean you should stop eating fresh produce, but just like your mom taught you, wherever your fresh fruits and vegetables are from, they need to be washed carefully to remove contaminants.

Many people who are infected with rat lungworm can be symptom-free, but other infections can lead to weeks to months of severe pain, possible paralysis and even death.

This 2014 paper confirms that the disease is found in many different kinds of snails and slugs throughout the Hawaiian Islands.

“We have now shown that nearly a third of the non-native snail species established in the Hawaiian Islands are carriers … along with two native species (Philonesia sp., Tornatellides sp.),” the paper says.

All three of the rat species known to Hawai`i are carriers: the Norwegian, black and Polynesian rats.

Here is the Hawai`i State Department of Health fact sheet on the disease. 



© Jan TenBruggencate 2017

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