The official rat lungworm disease case count from government authorities is likely an underestimate, and exposure to the parasite is much more common than people may realize, according to a new study led by the University of Hawaii Hilo.

An invasive spinal tap is currently the only definitive test for detecting the parasite, which could keep patients off of the record books.

This phenomena is highlighted by a discrepancy between self-reported but validated cases of rat lungworm disease and the official count offered by the Hawaii Department of Health and the Hawaii Health Information Corp., published in the The American Journal of Tropical Medicine and Hygiene.

The study’s findings reemphasize a need for improving diagnostics, researchers say.

Rat Lungworm Case count

The number of people living with rat lungworm disease is likely higher than official government counts.

Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo

“A lot of patients say they do not want to have a lumbar puncture, but if they don’t have a lumbar puncture, they’re not a confirmed case,” said Dr. Susan Jarvi, lead author of the study and head of the rat lungworm disease research team at the UH Hilo Department of Pharmaceutical Sciences.

The blood tests discussed in the study also showed people who believed they had never come into contact with the parasite had indeed been exposed. Low-level exposure may cause symptoms that could be brushed off as the common flu. The most severe cases can cause gastrointestinal and neurological damage.

sue jarvi in action

Dr. Susan Jarvi studies the angiostrongylus cantonensis parasite at the University of Hawaii Hilo.

Courtesy Susan Jarvi

Rat lungworm disease still eludes many medical personnel who are not familiar with it. Patients can suffer for weeks without knowing their affliction because of its varied symptoms. Additionally, the infection may already have progressed by the time a patient is officially diagnosed, which can have serious long-term medical effects.

Several efforts are underway at the lab to expedite the diagnosis process for the disease at the UH Hilo laboratory. Researchers are developing two kinds of blood tests — the first for parasitic DNA and the second for antibodies developing within the human system to combat it. They could serve as supplementary evidence of the presence of the disease.

“We want to develop a blood-based diagnostic because people are much more likely to get tested,” Jarvi said.

‘Skin on Fire’

When Joe Bowman first went to the emergency room at Ka’u Hospital on the Big Island with excruciating pain throughout his body, he said the doctors told him his fibromyalgia was flaring up and sent him home.

But when the pain persisted, his friends gave him a ride back to the ER the next evening. Again he was discharged, this time with a nerve painkiller in his pocket, despite his attempts to tell doctors the pain was beyond any level fibromyalgia had caused him. Bowman remembers lying in the grass outside, unable to move, when a security guard ushered him off the campus.

“I was gritting my teeth trying to keep my screaming down, but every time I opened my mouth I was yelling because I couldn’t help it,” he said. “I didn’t want to be seen like that. I was getting worse rapidly and just didn’t have the strength for anything I was in so much pain.”

Joe Bowman Hospital

Joe Bowman sought help at the emergency department of Ka’u Hospital twice and would go on to be hospitalized at three hospitals on the West Coast until he got his diagnosis.

Courtesy Kimberly Bowman

He decided to take the flight he had scheduled for California, and called his mother.

“He literally said, ‘I’m calling you because I’m not sure I’m going to survive the flight because I feel this bad and no one can tell me what’s wrong,’” Kimberly Bowman said. “He just got on the plane because he didn’t know what else to do.”

He spent the flight lying at the feet of a few empathetic strangers seated in the very last row on the plane.

Bowman used to work as a carpenter in Puna, run two miles a day, climb coconut trees and swim in the ocean. When he arrived in California, he was nearly unrecognizable, having lost about 50 pounds within about a week and a half.

It wouldn’t be until three more hospitalizations over a span of three months that he would receive the news from a federal laboratory that he had rat lungworm disease.

Global Hotspot

Hawaii has become a global hotspot for rat lungworm disease in recent years. All nine cases confirmed in 2019 were acquired in Hawaii County.

The study, “Estimating Human Exposure to Rat Lungworm on Hawaii Island,” is the first attempt to estimate human exposure to the parasite in the U.S. and explores the potential for blood testing to more quickly detect disease. During the process, researchers discovered antibodies developing in Big Island residents who thought they had never come in contact with the parasite.

John Jacob examines the rat lungworm parasitic larvae in the laboratory at UH Hilo, where research has found blood testing could be an early indicator of human exposure to the disease.

They found that Big Island participants had higher exposure rates than those reported in the parasitic nematode’s areas in China, where it is endemic. Seropositivity, or having blood serum that tests positive for the rat lungworm pathogen, has ranged from 14% to 20% in China; Big Island participants’ ranged from 22% to 30%.

“These results suggest the number of humans exposed to A. cantonensis may be greater than the number of cases previously reported by the Hawaii Department of Health,” the study states.

This study is also the first attempt to describe the disease’s wide-ranging symptoms. The most mild cases have flu-like illness, while the most severe cases can lead to coma, long-term disability and death.

It’s so mysterious that the medical and scientific community from around the globe is reaching out to the UH Hilo rat lungworm laboratory on the suspicion that a patient caught it while in Hawaii.

“We get so many calls,” Jarvi said, noting inquiries come from as far away as Canada and Italy. “I don’t have a secretary to keep track of all this stuff.”

Many Hospitals Unequipped

Rat lungworm stands out among tropical parasitic diseases because of the neurological harm it can cause.

“There’s a lot of parasites out there, but not all of them go to the brain,” she said. “Rat lungworm does.”

The parasite’s larvae spread via rat feces and mature in host carriers such as slugs or even coqui frogs. They prefer to make their way into rats’ pulmonary arteries, hence the disease’s colloquial name.

Humans are most commonly exposed by accidentally eating parasite hosts such as small slugs or snails hiding among produce like lettuce. People can also get sick after intentionally eating uncooked infected shrimp or mollusks — that’s the scenario for most patients who have fallen ill in Thailand and China.

In the past 12 months alone, three lawsuits have been filed against Hawaii eateries for serving meals that contained small slugs that plaintiffs allege exposed them to the disease.

But those who have seen slugs are among a rare set of patients who have an inkling that animal carriers are how they probably caught the disease.

Bowman has no idea how he contracted the parasite, but he is sure he didn’t eat a slug. He has his own theory — he fell ill soon after a day working in the dirt, removing some trees for a friend. Perhaps microscopic larvae made their way into his mouth. Civil Beat reviewed his hospital discharge paperwork to confirm that he was admitted to each of the hospitals and later diagnosed with the disease.

joe bowman big isle

Joe Bowman enjoyed hiking and swimming before he fell ill with rat lungworm disease.

Courtesy Joseph Bowman

Dr. Jon Martell, the chief medical officer at Hilo Medical Center, estimates about half of the patients he’s seen have no idea how they got exposed. Some patients have come to the hospital with symptoms as varied as headaches, facial droop, bad focus, or bladder pain. Others may go weeks without experiencing those issues.

“They practice good food hygiene,” he said. “They are not aware of any snails or slugs, they’re not on a catchment system, and they just don’t know. That makes it harder.

“It isn’t like the measles or chickenpox, where you see something that’s characteristic and go, ‘Oh,’ and know what that is,” he added.

The spokeswoman for Ka’u Hospital and Hilo Medical Center, Elena Cabatu, citing privacy rules, said she could not discuss Bowman’s story or confirm whether he was a patient without his permission.

Cabutu, who leads the hospitals’ rat lungworm disease patient survivor support group did say she has heard similar stories. “I’ve heard from patients who ended up going to the mainland, or maybe they were visitors, and they had multiple ER visits,” she said. “We’re trying our best to minimize those types of situations.”

To avoid similar scenarios in the future, she and Martell plan to visit more Big Island hospitals to make sure emergency room frontline staff are briefed.

“We are considered the ground zero of hospitals in the state, perhaps in the country, in caring for folks with rat lungworm disease, so we have quite a huge responsibility on our hands to spread best practices and inform the community,” Cabatu said.

Jarvi believes more doctors in Hawaii County are aware than they were before. But constant turnover among medical personnel there could also be an issue, she said. In some cases, she’s heard from patients who have been sent home from the emergency room with Tylenol.

Martell has met many patients infuriated with the lengthy process of diagnosis.

“I don’t want to minimize the times when the medical system has failed them, but a lot of times it is because there is no easy, accurate and appropriate way to make that diagnosis off the bat,” Martell said.

Diagnostic Hurdles

There are only two laboratories in the nation that will provide a diagnostic medical confirmation — the Hawaii Department of Health’s State Laboratories Division in Pearl City and the U.S. Centers for Disease Control and Prevention — that is, if the patient provides an eligible sample of cerebrospinal fluid.

Bowman, weak and dazed by hallucinations, said he sought help at four hospitals in three states until he got his opportunity, and even then, it was by chance.

Both Bowman and his mother suspected it was rat lungworm disease, but say doctors wouldn’t listen to their hypothesis.

After staying at a hospital in Weaverville, California, he was referred to Shasta Regional Medical Center in Redding, California, where he said doctors treated him as schizophrenic and noticed that he had signs of a possible stroke — an odd sign for someone 27 years old.  

Finally, a few ultrasounds and two spinal taps later, doctors told him they found an infection in his spinal cord and brain, and there was an alien parasite they couldn’t identify.

“No one in the hospital had ever seen anything like it,” Kim Bowman said.

Kim Bowman

Kimberly Bowman witnessed her son’s months-long harrowing journey to several hospitals as they tried to get answers about his pain that was later confirmed to be rat lungworm disease.

Courtesy Kim Bowman

A spokeswoman for the CDC said testing at its national laboratory can take up to two weeks, but state laboratories must vet samples first. Bowman said it took another six weeks until CDC confirmed the disease. By then, it didn’t make any difference to them. The parasite’s process was already well underway.

With no set treatment protocol, the only thing her son could do was try to survive the pain. It felt like torture when nurses would do something as simple as taking his vitals.

“Every hair on my body felt like a knife stabbing me,” he said.

Had Bowman been tested in Hawaii, it might have taken a few days.

Department of Health Spokeswoman Janice Okubo said the department has been able to turn around a confirmation within 48 hours since it began collaborating with the CDC in 2016.

“Our health department collaborated with CDC to develop a molecular test for angiostrongylus DNA in cerebrospinal fluid to confirm the disease in patients,” Okubo said.

Still, there are strict guidelines for cerebrospinal fluid testing that can disqualify some patient samples, according to Martell.

High Exposure

Higher rates of exposure among Big Island residents could be related to the vast number of slugs and rats that have tested positive for the parasite on the island.

In Puna, more than three-quarters of semi-slugs randomly tested were found to be infected, along with 100% of randomly tested rats’ lungs. In Hilo, 94% of randomly tested rats were infected.

The remarkable infection rates among animals on the Big Island, which had the highest infection rates among animals of all the Hawaiian islands, may contribute to the increased risk of exposure to humans.

Semi-slugs, which were first discovered in Hawaii in the late 1990s, appear to be the major culprit for spreading the parasite among animals, according to Jarvi.

“These guys climb into catchment tanks, coffee cups, everywhere,” she said, noting researchers have easily trapped slugs for testing by leaving moist dog kibble under black plastic bags. “They’re super mobile. They do very well in residential areas.”

This semi-slug was found in Hana, Maui. Semi-slugs are considered to be behind the high infection rates among animal carriers of the rat lungworm parasite on the Big Island.

Tad Bartimus/Civil Beat

The slugs are mostly looking for shelter to lay eggs and for their favorite foods like sweet fruits, coconut and lettuce.

Parasitic exposure among Big Island residents could also be related to widespread use of rainwater catchment for drinking water. Nearly 80% of the study’s 435 participants reported using catchment systems.

Researchers have found semi-slugs drowned inside catchment tanks, and infective larvae can survive in water for several weeks, according to the study. It’s still unknown if drinking water is a risk for significant exposure.

It is possible that lower levels of exposure to the parasite could trigger immunological protections, but it hasn’t been studied among humans, only rats.

Solving The Mystery

The Frequently Asked Questions page on the UH pharmacy school’s website illustrates the confusion and worries surrounding the disease online.

“Can marine gastropods or other mollusks carry this parasite e.g. opihi?” one person asked. “Is the slime of the semi-slug dangerous too?” asked another.

The answer is yes — fresh water opihi can carry the parasite, as well as prawns and frogs, maybe because rat feces and larvae can make their way into the water. And it’s still not known if direct skin contact can cause someone to fall ill.

The laboratory is working to solve other mysteries surrounding the disease.

One of the UH Hilo lab’s ongoing studies is an investigation of which of the commercially available produce washes is most effective at killing the parasitic larvae. Researchers are also looking at whether or not UV light and anti-parasitic drugs can kill the nematode’s larvae.

The laboratory will continue to collect blood samples to strengthen the evidence that blood tests can detect the parasite quickly. But even blood tests have limitations: they’ll only yield results within a certain time frame.

Kim and Joe Bowman

Joe Bowman and his mother Kimberly moved to Washington state while he recovers from the tropical parasitic disease.

Kimberly Bowman

Bowman said he hopes the blood tests can be vetted as soon as possible to save future patients the trauma of going weeks or months without a diagnosis and proper pain medication.

He spends most of his days sitting still, since nerve and muscle pain lingers in persistent waves. It takes a full day of rest to recover from climbing the two flights of stairs to his new apartment in Washington state.

“I’m ruined now forever and I was in tip top shape,” he said. “It made me question everything, going through that journey, because of the way I was treated.”

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