University of Hawaii researchers have found that rat lungworm is poised to expand its range under the spell of climate change, a fact that could leave more people than ever vulnerable to the infectious disease.

A study appearing in the science journal Parasitology says the debilitating disease that has made headlines in Hawaii in recent years is expanding throughout the tropics and is likely to become more common on the mainland as temperatures warm in the coming decades.

In Hawaii, UH researchers found rat lungworm on five of the six largest islands, where it tended to occur in warmer and rainier windward areas but not exclusively. It also was detected in such leeward locales as Kailua-Kona on the Big Island, Kihei on Maui and Kekaha on Kauai.

“It’s not going to go away,” said Robert Cowie, research professor with UH’s Pacific Biosciences Research Center, who helped direct a team of scientists, including lead author Jaynee Kim, who worked on the study for her UH master’s thesis.

Rat lungworm was first detected in Hawaii in 1960, with some 20 cases having been recorded in the islands by the mid-1970s.

The disease “fell off the radar” afterward, Cowie said, but it appeared to make a comeback around 2004. And in recent years the state has averaged six to eight cases a year, although 18 cases were confirmed in 2017.

While those numbers are relatively low in comparison with other infectious diseases, rat lungworm can be particularly harsh, causing excruciating headaches, nerve damage, temporary paralysis, comas or even death. It is capable of leaving serious, long-term disabling consequences for those who are stricken.

The disease involves the interaction of rats, the primary hosts, and snails and slugs, intermediate hosts, which can pass along the worms, a parasitic nematode, to victims. Humans can get the disease when they accidentally eat a snail or slug hidden amid their produce.

The state Legislature last year granted the Health Department $1 million over two years to help control the spread of rat lungworm. Health officials are working with experts to develop guidelines for schools, farms, food establishments and physicians on how best to prevent the disease.

The UH researchers used molecular techniques to screen 1,271 snails and slugs in 37 species from 182 sites across the islands to detect the presence of rat lungworm in the snails and slugs.

Mathematical models allowed them to predict the likely areas where rat lungworm will spread, comparing today’s climate with projected conditions in the year 2100.

The study’s Hawaiian Island projections were used as a model to show that rat lungworm can spread into more temperate regions of the world.

As of now, Cowie said, rat lungworm is considered globally as a neglected emerging infectious disease, but that is likely to change.

In Hawaii the disease is likely to expand and especially into higher elevations as the climate warms, according to the study.

Researchers found the highest proportion of infected slugs and snails on Kauai and Hawaii, while the the lowest proportion was on Oahu, possibly because Oahu has more freshwater snails, which are less likely to encounter rat feces, the study said.

The disease wasn’t found on Lanai, according to the study, but that island did have a recent case where it is possible that contaminated produce was shipped to the island or that the victim may have become infected on another island.

Cowie cautioned that it is impossible to say that rat lungworm is absent from areas where researchers couldn’t find it.

“People should not assume, based on this study, that rat lungworm is not in their yards,” he said.

On the other hand, Cowie said, “It’s not something to be hysterical about. You need to wash your produce, and that’s something you should be doing anyway to avoid (food poisoning from) E. coli and salmonella.”

The study was funded by the U.S. Department of Agriculture; the National Science Foundation; the Ecology, Evolutionary and Conservation Biology program at the University of Hawaii; the American Malacological Society; and the Hawaiian Malacological Society.