Rat Lungworm Disease Reaches California, Lessons from Hawaii

As the parasitic disease spreads, California can learn from Hawaii's experience on prevention and diagnosis.

Mar. 11, 2026 at 7:38pm

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Rat lungworm disease, long associated with Hawaii, has now been detected in California at the San Diego Zoo, raising concerns that the debilitating illness could become more widespread. Hawaii has seen over 80 confirmed cases of the disease from 2016 to 2026, offering a preview of what California residents and doctors should know about prevention and diagnosis.

Why it matters

Rat lungworm disease can cause severe neurological complications in humans, and awareness of the disease has altered the way some Hawaii residents purchase and prepare produce. As the parasite spreads, California needs to learn from Hawaii's experience to prevent and properly diagnose cases.

The details

The disease is caused by the parasite Angiostrongylus cantonensis, which begins its life cycle in rats. The larvae are then passed to snails and slugs through rat feces. Humans can become infected if the microscopic larvae are accidentally ingested, most commonly through contaminated produce. In humans, the parasite travels to the brain, where it can cause severe headaches, nerve pain, and other neurological issues. Prompt treatment with antiparasitic medication can help people recover, but the disease is considered highly underdiagnosed.

  • The parasite that causes rat lungworm disease was detected in California at the San Diego Zoo in 2026.
  • From 2016 to 2026, Hawaii has seen over 80 confirmed cases of rat lungworm disease.

The players

Susan Jarvi

A Hawaii researcher who has studied rat lungworm in the state for more than a decade and recently retired.

Dr. Jon Martell

A former Hilo physician who has treated cases of rat lungworm disease in Hawaii.

California Department of Food and Agriculture

The agency that has rated the potential for the invasive semi-slug, a major carrier of the rat lungworm parasite, to spread in California.

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What they’re saying

“It's probably more prevalent, probably across the country, especially in the southern portions. It's probably all over the place. We know it's in Louisiana, Texas, Georgia, Florida, so it's probably spread again.”

— Susan Jarvi, Researcher (SFGATE)

“They can't get out of the brain, so they keep wandering around inside your brain trying to get out, and then they die in your brain.”

— Dr. Jon Martell, Former Hilo Physician (SFGATE)

What’s next

The California Department of Public Health has not yet responded to requests for comment on how the state plans to address the spread of rat lungworm disease.

The takeaway

As rat lungworm disease spreads beyond Hawaii, California must learn from the Aloha State's experience to raise public awareness, improve clinician education, and implement effective prevention strategies to protect residents from this debilitating parasitic illness.