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Rat Lungworm Disease

Adult male and female (with red and white barber-pole spirals) rat lungworms in the pulmonary artery of a rat (Photo: Nicole Yoneishi, Medeiros lab).

Randi Rollins, PhD student in Robert Cowie’s PBRC lab, recently published the second in a pair of papers addressing the determinants of the levels of infection of snails and slugs with the parasite known as the rat lungworm (Angiostrongylus cantonensis), the cause of serious disease (neuroangiostrongyliasis) in people and animals in Hawaii. Co-authors on the papers were Matt Medeiros (PBRC Assistant Professor), Vida Echaluse (REU intern from Saipan in Matt’s lab), and Cowie.

The first paper1 showed that within a particular species larger individuals were more likely to be infected than smaller ones. But the density of worms in an individual infected snail was unrelated to its size – the species being the key in this case. Thus older individuals of small species would be more likely to be infected than much younger individuals of larger species. And since an often suggested pathway of human infection is by accidentally ingesting a small snail or slug hidden among leafy salad greens, the results point to the small species perhaps being more important in transmission of the parasite to people.

The second study2 showed that overall, snails from rainy, cool, heavily vegetated sites had higher infection levels than snails from dry, hot sites with less green vegetation, but that the frequency of individual snails being infected varied among species. The risk of human infection is thus greater in locations with higher rainfall, lower temperature and more vegetation cover but this depends on the host species. Moreover, the severity of neuroangiostrongyliasis symptoms is likely to be greater in locations with higher rainfall, lower temperature, and more vegetation because of the higher numbers of infectious larvae in all infected host species.

Together, these studies highlight the environmental and species-specific variables that influence infection levels in the snails and slugs that transmit the disease-causing parasites, with key implications for understanding the potential for neuroangiostrongyliasis (rat lungworm disease) in different environments.

The papers are contributions to the MARG (Mānoa Angiostrongylus Research Group), an informal group of UH Mānoa researchers from the School of Ocean and Earth Science and Technology (PBRC), the College of Tropical Agriculture and Human Resources (Department of Human Nutrition, Food and Animal Sciences), and the John A. Burns School of Medicine, established in 2019 by Cowie to foster collaboration across Mānoa units and to highlight the significant rat lungworm disease research being conducted here at UH Mānoa.

Randi Rollins received the 2020 Graduate Students Organization (GSO) Merit Based Award for Research at the Ph.D. level for her work on rat lungworm disease. She is currently the GSO Grants and Awards Manager.

1 Medeiros, M.C.I., Rollins R.L., Echaluse, M.V. & Cowie, R.H. 2020. Species identity and size are associated with rat lungworm infection in gastropods. EcoHealth 17(2): 183-193

2 Rollins, R.L., Cowie, R.H., Echaluse, M.V. & Medeiros, M.C.I. 2021. Host snail species exhibit differential Angiostrongylus cantonensis prevalence and infection intensity across an environmental gradient. Acta Tropica 216: 105824.

See also:
University of Hawai‘i News: Environmental factors, species influence rat lungworm infection in snails
University of Hawai‘i News: Grants for grad students’ research, professional development available
School of Ocean and Earth Science and Technology (SOEST) News: Rat lungworm research advances through UH collaboration

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