The state yesterday warned people to wash produce thoroughly after several Big Island residents contracted a rare form of meningitis, leaving two of the patients in comas.

Graham McCumber, 24, and Silka Strauch, 38, both Puna residents, became progressively sicker in December, presumably from accidentally eating tiny slugs on home-grown vegetables, friends and relatives said.

A friend of Strauch's, Zsolt Halda, also was hospitalized but has been released.

All contracted a rare form of meningitis — or infection of the spinal fluid — called eosinophilic meningitis or angiostrongyliasis. It is caused by the rat lung-worm parasite, or Angiostrongylus cantonensis, and is spread when snails and slugs eat parasite-infested rat dung and move onto vegetables, where they are eaten by humans.

Strauch has been hospitalized mostly at Hilo Medical Center since Dec. 8, said her friend Kristina Mauak, and has been in a coma for about three weeks. Strauch also spent several days at The Queen's Medical Center in Honolulu sometime after Dec. 8.

McCumber, who has been in a coma about 10 days, first complained of illness the week before Christmas, said his uncle, Geoff Rauch.

McCumber, a carpenter's apprentice, is at The Queen's Medical Center, where medical tests show the parasites have caused damage to his brain, Rauch said.

"It's a nightmare for us for sure," Rauch said of his family's vigil by his nephew's bedside. "None of us want to eat salads right now. ... If he comes out of this coma, we'll all be overjoyed."

According to Rauch and Mauak, McCumber and Strauch each first complained of itching and a rash that escalated over several days to pain so bad it hurt for anything to touch their skin.

Yesterday's advisory by the state Department of Health comes in the wake of six probable cases of rat lung-worm in Hawai'i in 2008. All those who got sick were residents of the Big Island and regularly ate fresh raw vegetables from backyard gardens.

Dr. Francis Pien, an infectious disease consultant on O'ahu, said he has treated at least 20 cases of rat lung-worm disease in his 35 years of practice.

"Everybody else got well," Pien said, including one local patient who got sick while on the Mainland after eating raw 'opihi in Hawai'i. "They've all made essentially complete recoveries."

State epidemiologist Dr. Sarah Park said the intensity of three recent cases prompted the state Health Department to issue the warning yesterday, urging Hawai'i residents to thoroughly wash home-grown vegetables and avoid eating uncooked slugs or snails.

Thirty-three suspected cases of the disease have been reported on Maui, the Big Island, Lana'i, and O'ahu since 2001, Park said.

The numbers represent only cases reported by doctors.

It's not known how many people had a milder form of the disease, with headache, joint pain and other symptoms, which can pass on its own without treatment.

The body's allergic response causes most of the symptoms, Pien said.

More serious cases can cause paralysis, blindness and death, according to the Centers for Disease Control.

That something so serious could strike young adults in good health is sending shock waves through the Puna District, said Rauch, a proponent of organic, locally grown produce.

Prevention is the key to avoiding the disease, Park said. She recommends washing each lettuce leaf by hand, looking closely for tiny slugs that can be no bigger than the nose of Thomas Jefferson on a nickel.

"We are in no way saying that vegetables are unsafe," Park said. "I would advocate locally grown vegetables — just wash them."

Halda and Strauch "were in the habit of making smoothies with greens in them from their garden," Mauak said.

"She's still in a very dangerous state, fighting for her life," Mauak said of Strauch, a yoga instructor who has lived on the Big Island for about seven years. Strauch's parents flew in from Germany and her brother is coming this weekend, she said.