A review of a long time of research revealed greater than a dozen sorts of animals along with slugs and snails have caused rat lungworm disease in people world wide.

Researchers from the University of Hawai’i at Mānoa and the University of London (UK) combed through nearly 140 scientific studies published between 1962 and 2022 and located 32 species of freshwater prawns/shrimp, crayfish, crabs, flatworms, fish, sea snakes, frogs, toads, lizards, centipedes, cattle, pigs, and snails can act as carriers of the rat lungworm parasite (Angiostrongylus cantonensis). Of those, no less than 13 species of prawns/shrimp, crabs, flatworms, fish, frogs, toads, lizards, and centipedes have been related to causing rat lungworm disease in humans.

This work was the master’s degree thesis research of the primary creator, Helena Turck, as a part of a graduate program in One Health jointly run by the Royal Veterinary College and the London School of Hygiene and Tropical Medicine, each a part of the University of London, UK. Robert Cowie, senior creator on the study and school member within the UH Mānoa School of Ocean and Earth Science and Technology (SOEST), supervised Turck’s research remotely throughout the pandemic and co-authored the brand new publication. Professor Mark Fox of the Royal Veterinary College can also be a co-author of the study.

Cowie explained that the rat lungworm has a fancy life cycle that involves slugs and snails as so-called “intermediate” hosts and rats as “definitive” hosts by which the worms reach maturity and reproduce. Rats turn out to be infected once they eat an infected snail or slug. People also turn out to be infected once they eat an infected snail or slug, and this could result in serious illness and infrequently death.

Humans, accidental hosts

“But people may get infected in the event that they eat so-called paratenic hosts, that are also generally known as carrier hosts,” said Cowie, who’s a research professor within the Pacific Biosciences Research Center at SOEST. “These are animals that turn out to be infected by eating infected snails or slugs, but by which the worms cannot develop to maturity as they do in a rat. Nonetheless, in such hosts the worms turn out to be dormant, but still infective. And if one in all these hosts, or a part of one, is then eaten raw by an individual – an accidental host – development can proceed, but only up to some extent.”

That time is once they are within the person’s brain, where they’re moving around, feeding, and growing. But then the worms die. The damage to the brain and the large inflammation that results once they die is primarily what causes the symptoms of rat lungworm disease.

“It will be important to know not only that snails and slugs can transmit rat lungworm parasites to humans but in addition which other animals – which paratenic hosts – may achieve this,” Cowie said. “So the goal of the study, was to drag all the knowledge on paratenic hosts and their role in transmission of rat lungworm disease, previously scattered in diverse publications and obscure reports, together into one place and develop a worldwide understanding of their diversity and role in disease transmission.”

Rat lungworm disease across the globe

Rat lungworm disease is at present confined largely to the tropics and subtropics, notably parts of South and Southeast Asia, where it probably originated, southern China, Taiwan, southern Japan, various Pacific islands and archipelagos, and more recently Brazil, Caribbean islands, and Australia. The parasite has also been reported from the Canary Islands and Balearic Islands of Spain, in addition to southeastern parts of america, where there have been a handful of cases of rat lungworm disease. Climate change may result in its further spread into currently more temperate regions.

Hawai’i is a worldwide center of the incidence of rat lungworm disease, and indeed it was in Hawai’i where the connection between the parasite and the disease was first discovered, by University of Hawai’i and US government scientists within the early Sixties.

“Several species able to acting as carriers (paratenic hosts) are present in Hawai’i, including flatworms, centipedes, coqui frogs, and cane toads,” said Cowie. “While people in Hawai’i are unlikely to eat these animals, it is just not unknown for people to achieve this on a dare, and turn out to be seriously sick. Elsewhere, certain paratenic hosts are eaten for supposed health reasons – frogs in Taiwan and Japan, or to boost virility – lizards in Thailand.”

Domestic animals, especially dogs and horses, may turn out to be infected by the rat lungworm parasite, including in Hawai’i, probably mostly from unintentionally or deliberately eating snails or slugs.

Stopping infection

There are several things people can do to forestall infection by rat lungworm.

“Awareness of which species may harbor the parasite is critically necessary each in Hawai’i and more widely,” said Cowie. “These animals shouldn’t be consumed raw. Moreover, wash all vegatables and fruits well under running water and inspect them for slugs, snails and possible other hosts comparable to flatworms in order to avoid inadvertently eating them or parts of them.”

Source:

University of Hawai’i at Mānoa