Water transmission potential of Angiostrongylus cantonensis: larval viability, and effectiveness of rainwater catchment sediment filters

Abstract

16 Neuroangiostrongyliasis, caused by Angiostrongylus cantonensis, has been reported in Hawaiʻi 17 since the 1950's. An increase in cases is being reported primarily from East Hawaiʻi Island, 18 correlated with the introduction of the semi-slug Parmarion martensi. Households in areas 19 lacking infrastructure for water must use rainwater catchment as their primary domestic water 20 supply, for which there is no federal, state, or county regulation. Despite evidence that 21 contaminated water can cause infection, regulatory bodies have not addressed this potential 22 transmission route. This study evaluates: 1) the emergence of live, infective-stage A. cantonensis 23 larvae from drowned, non-native, pestiforous gastropods; 2) larvae location in an undisturbed 24 water column; 3) longevity of free-living larvae in water; and 4) effectiveness of rainwater 25 catchment filters in blocking infective-stage larvae. Larvae were shed from minced and whole 26 gastropods drowned in either municipal water or rainwater with >94% of larvae recovered from 27 the bottom of the water column. Infective-stage larvae were active for 21 days in municipal 28 water. Histological sectioning of P. martensi showed proximity of nematode larvae to the body 29 wall of the gastropod, consistent with the potential for shedding of larvae in slime. Gastropod 2 30 tissue squashes showed effectivity as a quick screening method. Live, infective-stage larvae were 31 able to traverse rainwater catchment polypropylene sediment filters of 20 µm, 10 µm, 5 µm, and 32 1 µm filtration ratings, but not a 5 µm carbon block filter. These results demonstrate that live, 33 infective-stage A. cantonensis larvae can and do emerge from drowned snails and slugs, survive 34 for extended periods of time in water, and that the potential exists that they enter the household 35 water supply. This study illustrates the need to better investigate and understand the potential 36 role of contaminated water as a transmission route for neuroangiostrongyliasis. 37 38 Introduction 39 The nematode Angiostrongylus cantonensis is established throughout the main Hawaiian Islands 40 with the possible exception of Lānaʻi [1, 2, 3]. The complex lifecycle of this parasite has been 41 well-described in the literature [4, 5, 6, 7]. In Hawaiʻi, Rattus rattus and Rattus exulans are 42 important definitive hosts, and many gastropod species are effective intermediate hosts including 43 Achatina fulica, Euglandia rosea, Laevicaulis alte, Limax maximus, Parmarion martensi and 44 Veronicella cubensis [1, 2, 8]. The third stage larva (L3) is harbored in the intermediate host, and45 it is this larval stage that is infective to rats and accidental hosts, including humans, as the L3 46 larvae can safely pass through the acidic environment of the mammalian gut. There are also 47 paratenic hosts that can carry the infective stage larvae; these include shrimp, prawns, crabs, 48 frogs, water monitor lizards, centipedes, and some planarians [7. 9, 10, 11, 12]. Of planarians, 49 the predacious Platydemou...

Validation of a death assay for Angiostrongylus cantonensis larvae (L3) using propidium iodide in a rat model (Rattus norvegicus)

“…Parmarion martensi are semi-slugs known to have high infection levels of A. cantonensis in Hawaii (Hollingsworth et al ., 2007). Semi-slugs were collected from the University of Hawaii at Hilo campus and immersed in 50 mL dH 2 O in 50 mL Falcon tubes for 72 h. The bottom 15 mL from each tube was transferred to a culture plate (100 mm × 15 mm) (Howe et al ., 2019) and observations were made under a dissection microscope (Wild Heerbrugg M4A APO) at 10–40× to detect the presence of larvae. Live larvae with S and Q swimming movements attributed to A. cantonensis L3 larvae (Lv et al ., 2009) were collected using a 20 µL micropipette and transferred into 0.5% pepsin-0.5% HCl (pH 1.41) solution for 30 min at room temperature (Ash, 1970; Wang et al ., 1991).…”

“…Tissue samples were stored frozen until DNA was extracted for PCR. DNA extractions and real-time PCR were carried out as described (Jarvi et al ., 2012; Howe et al ., 2019).…”

“…The L3 stage is the only stage known to infect vertebrate hosts, including the definitive (rat) host and accidental hosts such as humans (Mackerras and Sandars, 1955). Transmission to humans is thought to be due to ingestion of L3 larvae in infected gastropods, on improperly washed produce (Heyneman and Lim, 1967; Wang et al ., 2008) or in contaminated water (Cheng and Alicata, 1964; Richards and Merritt, 1967; Crook et al ., 1971; Howe et al ., 2019). The invasive semi-slug, Parmarion martensi , is an extremely efficient host and is thought to be the primary cause of the increase in severe neuroangiostrongyliasis in Hawaii since its introduction in 2004 (Hollingsworth et al ., 2007; Jarvi et al ., 2018).…”

Angiostrongylus cantonensis and neuroangiostrongyliasis (rat lungworm disease): 2020

“…Most human infections are derived from gastropods; a less significant source is provided by various paratenic hosts (such as freshwater shrimps, frogs, centipedes, or monitor lizards), which can harbour L3s after ingesting gastropods, and so reflect geographical/cultural idiosyncracies. Another likely vehicle of infection is drinking water contaminated with L3s released by decomposing molluscs (Howe et al, 2019). The role of gastropod mucus deposited on vegetable greens remains inconclusive.…”

Demographics of the semi-slug Parmarion martensi, an intermediate host for Angiostrongylus cantonensis in Hawai‘i, during laboratory rearing

“…Standardized rearing methods for P. martensi would facilitate the development of information on biotic and abiotic factors related to vector competence and transmission, and evaluation of management tactics. Recent studies in Hawai'i have used field-collected P. martensi as a source of A. cantonensis for experimentation (Jarvi et al, 2012(Jarvi et al, , 2015(Jarvi et al, , 2019Howe et al, 2019); however, wild-caught individuals may also be carrying other nematode species (Howe et al, 2019). Evaluation of management tactics relies on performance comparisons between treated and untreated control groups, which can only be accomplished with a reliable rearing system.…”