Invasive Slug Aids Spread of Rat Lungworm

Hawaii’s invasive species problem has now become a human health risk as the invasive Semi-slug increases the spread of Rat Lungworm.

The lifecycle of Angiostrongylus cantonensis, also known as Rat Lungworm, is simple – it involves a worm larvae, an invasive slug, and an invasive rat. The lifecycle is relatively unremarkable until the parasite finds its way into humans, which has been the case as seen in Hawaii’s recent outbreaks.

A. Cantonesis is a small nematode (roundworm) that infects invasive slug called a Semi-slugs. which are native to South-East Asia but have become invasive and a vector for this disease in Hawaii. Although the parasite has always existed in Hawaii, a boost to the invasive semi-slug population has led to increased risk to humans. Researchers have found that 70% of the Semi-slug population carries the parasite, as does 90% of the rat population in Hawaii.

In the parasite’s normal lifecycle, the worm larvae is consumed by the Semi-slug, which is then eaten by an invasive rat. The parasite makes a home out of the rat’s lungs. The rat excretes more worm eggs in its feces and the cycle repeats itself—unless larvae are unintentionally consumed by a person. Recent outbreaks in Hawaii are linked to people eating vegetables that have been exposed to Semi-slugs carrying the parasite.

island conservation rat lungworm lifecycle

The lifecycle of Rat Lungworm does not normally involve humans, but when it does the worm causes severe damage to the brain. Credit: Center for Disease Control

When the parasite does make it into the human body, there is no real way to stop the damage it causes. No antidote is available and even the test to confirm diagnosis requires a painful spinal tap. Once the parasite makes its way to the brain, it can cause extensive and irreparable damage and has side-effects reminiscent of meningitis. Dr. Sarah Park, an epidemiologist for the state of Hawaii commented:

It’s like having a slow-moving bullet go through your brain.

Typically Hawaii has 1-9 cases of Rat Lungworm every year, but in the past three months three cases have been confirmed on Maui alone. Overall, six cases have been reported on Maui which, if all are confirmed, would triple the number of cases the island has had in the past decade. In the past, most cases come from the Big Island where the Semi-slug is widespread, but the parasite now appears to be spreading to Maui.

Health officials are concerned over the outbreak and explained that the only way to prevent it is to wash fruits and vegetables thoroughly before eating them in order to remove any larvae. The parasite’s lifecycle might seem simple but researchers are only beginning to understand the impact the parasite and its invasive hosts have on humans.

Featured photo: People can contract Rat Lungworm by consuming compromised produce. Credit: Leonard Chien
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About Emily Heber

Emily is a recent graduate from UC Santa Barbara with a BS in Zoology. As a student, she discovered that she had a passion for the conservation of endangered species and their ecosystems. Her background in informal education has allowed her the opportunity to share her passion for animals with others, something she seeks to continue doing while working with the communication team. In her spare time, Emily enjoys exploring the amazing hiking trails found in Santa Cruz and tries to SCUBA dive whenever possible. Emily is excited to join the Island Conservation team and to help share the amazing work that is being done here.

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