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.
“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.
© Jan TenBruggencate 2017