Rare Parasite That Affects the Brain Spreading in Hawaii


Hawaii is experiencing a cluster of rat lungworm disease cases on the Big Island as well as on the island of Maui; a few suspected cases are still undergoing investigation.

Over the past three months, Hawaii has been seeing several cases of rat lungworm disease, particularly on the island of Maui, where the Hawaii State Department of Health (DOH) recently confirmed six cases; three cases were confirmed on the Big Island, according to CNN.

Rat lungworm disease is caused by a parasite known as Angiostrongylus cantonensis. Found only in rodents, according to the Centers for Disease Control and Prevention (CDC), the parasite is known to infect individuals “under unusual circumstances,” with the potential to affect the brain and the spinal cord.

A spokeswoman for the DOH, Janice Okubo, said that one case on the Big Island and three additional cases on Maui are also being investigated. The six cases that have already been confirmed on Maui consisted of four residents and two visitors. Of those cases on other parts of Hawaii, the confirmed cases were only in residents, according to a recent news release.

She added that usually, the DOH receives reports of one to nine cases of rat lungworm disease annually, and since 2007, there have only been two related deaths.

In an email, Okubo wrote, “The investigation is fluid and the cluster of cases, though not all confirmed, are very concerning.”

Although officials have not been able to confirm just how the individuals contracted the parasite, it is known that one can become infected by consuming raw or undercooked snails or slugs that are contaminated. However, the CDC states that individuals can also become infected by “eating raw produce (such as lettuce) that contains a small snail or slug or part of one.” Furthermore, animals such as freshwater shrimp, crabs, or frogs, are known to have been infected with the parasite in the past, and so it may be possible to contract the parasite by eating infected undercooked or raw animals; however, “the evidence for this is not as clear as for eating infected snails and slugs.”

According to Heather Stockdale Walden, PhD, assistant professor in the department of infectious diseases and pathology at the University of Florida, rat lungworm disease is not something new in Hawaii. In fact, the disease “has been endemic in Hawaii for at least 50 years, so it’s been there for a while.”

The CDC reports that although cases have been reported in Hawaii, “very few cases have been reported in the continental United States.” There have also been reports of infection in other parts of the world, such as Asia and the Pacific Islands.

Although some infected individuals do not present with any symptoms, or only experience fleeting, mild symptoms, the infection can result in eosinophilic meningitis, which is a rare type of meningitis.

According to Dr. Walden, “What happens is that the parasite gets into humans—humans are not the host that it can complete its life cycle in, as opposed to being in a rat—so when it gets in a human, it can get lost, and it will go to the brain, and it’ll stay there.” She continued, “When it gets to the brain, you can have eosinophilic meningitis.”

Infected individuals can also experience headaches, stiff necks, a tingling or painful sensation in the skin, a low-grade fever, nausea, and even vomiting.

Dr. Walden stated that the infection presents differently in adults compared with children. “In children, it’s more the nausea and vomiting, not so much the headache.”

The illness can last anywhere from two weeks to two months, and the incubation period ranges from one to three weeks on average. “However, an infection can incubate in only a single day or in six weeks,” reported CNN.

The CDC states that those infected with the parasite do not usually need to receive treatment because “the parasite dies over time, even without treatment.” In fact, even individuals who are unlucky enough to develop eosinophilic meningitis do not usually need antibiotics. Those who are infected can receive treatment to deal with the symptoms of the infections, “such as pain medication for headache or medications to reduce the body’s reaction to the parasite, rather than the infection itself.”

The good news is the infection cannot be spread from human to human.

So, how can individuals prevent themselves from infection? According to the Hawaii DOH:

  • DO NOT eat raw foods contaminated with the slime from snails or slugs or visible snails or slugs.
  • RINSE PRODUCE in potable water completely, and boil snails, freshwater prawns, crabs, and frogs for AT LEAST 3-5 MINUTES.
  • Do not handle snails and slugs with bare hands.
  • Control slugs and snails at your residence.
  • Cover your catchment tanks to prevent slugs and snails from having access.
  • Controlling rodents can also help control the rat lungworm

If you suspect you might be infected with rat lungworm disease, you should contact your healthcare provider immediately.

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