Distribution of Parmarion cf. martensi (Pulmonata: Helicarionidae), a New Semi-Slug Pest on Hawai‘i Island, and Its Potential as a Vector for Human Angiostrongyliasis¹

Abstract

The semi-slug Parmarion cf. martensi Simroth, 1893, was first discovered on O'ahu, Hawai'i, in 1996 and then on the island of Hawai'i in 2004. This species, which is probably native to Southeast Asia, is abundant in eastern Hawai'i Island, reportedly displacing the Cuban slug, Veronicella cubensis (Pfeiffer, 1840), in some areas. A survey in July-August 2005 found P. cf. martensi primarily in the lower Puna area of Hawai'i Island, with an isolated population in Kailua-Kona (western Hawai'i Island). It is now established in commercial papaya plantations, and survey participants reported it as a pest of lettuce and papaya in home gardens. Survey respondents considered P. cf. martensi a pest also because of its tendency to climb on structures where it deposits its feces and because of its potential to transmit disease. Individuals of this species were found to carry large numbers of infective third-stage larvae of the nematode Angiostrongylus cantonensis (Chen, 1935), the causative agent of human angiostrongyliasis and the most common cause of human eosinophilic meningoencephalitis. Using a newly developed polymerase chain reaction test, 77.5% of P. cf. martensi collected at survey sites were found infected with A. cantonensis, compared with 24.3% of V. cubensis sampled from the same areas. The transmission potential of this species may be higher than that for other slugs and snails in Hawai'i because of the high prevalence of infection, worm burdens, and its greater association with human habitations, increasing the possibility of human-mollusk interactions. The semi-slug Parmarion cf. martensi Simroth, 1893, is a recent introduction to the island of Hawai'i. The first record was made in the summer of 2004 in Paradise Park, a residential area in the district of Puna (East Hawai'i Island) (Arnold Hara, University of Hawai'i, pers. comm., 2005). The species was recognized as being similar to, or the same as, a semi-slug species collected for the first time on the island of O'ahu in 1996 and provision

Eosinophilic Meningitis Attributable to Angiostrongylus cantonensis Infection in Hawaii: Clinical Characteristics and Potential Exposures

“…Juvenile forms of P. martensi tend to be smaller than other slugs/snails and therefore, might be even less readily noticed on produce. 36 Furthermore, they reportedly are efficient at transmitting A. cantonensis , because a higher proportion are infected (compared with Veronicella cubensis , the dominant large mollusk species in the area), they have greater parasite burdens, and they tend to enter human habitats (including houses and water tanks). 36 Our understanding of transmission and the potential role of P. martensi is limited, in part because we were unable to identify a common source for this geographically and temporally dispersed cluster of suspected cases.…”

“…44 In particular, the introduction of Parmarion martensi may have been a factor in the clustering of suspected angiostrongyliasis cases, especially on the island of Hawaii. 23,36 This semi-slug was first documented on Oahu in 1996 and on the island of Hawaii in 2004. 36,44 Data from a study in 2005 suggest that there were increasing numbers of P. martensi in home gardens, particularly on the island of Hawaii;…”

“…Environmental studies found A. cantonensis larvae in slugs in the yards of the infant with a parasitologically confirmed case and two case-patients who shared a household. 35,36 The possibility of transmission through snail/slug slime trails on produce requires further investigation. Studies have detected A. cantonensis larvae and larval DNA in the slime trails of 12% of infected snails/slugs, but it is unclear whether the parasite can be transmitted in this mucus.…”

“…[40][41][42][43] Infection from consumption of unwashed, homegrown produce may have been compounded by changes in the snail/ slug host populations around the time of the outbreak. 23,36 In 2008, of 31 snail/slug species at selected nurseries in Hawaii, 29 (94%) species were alien to Hawaii, and 5 (16%) species had not previously been documented in the state. 44 In particular, the introduction of Parmarion martensi may have been a factor in the clustering of suspected angiostrongyliasis cases, especially on the island of Hawaii.…”

PCR-Based Detection ofAngiostrongylus cantonensisin Tissue and Mucus Secretions from Molluscan Hosts

“…All sequences obtained from the mollusks and mucus secretions analyzed in this study (as described above) were identical to the 18S rRNA sequence from A. cantonensis deposited in the GenBank database (accession number AY295804). However, cross-reactivity of the primers was detected when the PCR was applied to a larger set of snails and slugs that were collected for a geographical survey study of the presence of A. cantonensis in the molluscan fauna of Hawaii (16). Of 49 mollusks with a positive result in the PCR, 3 were found to be false positives for A. cantonensis by sequence analysis.…”