Abstract
Eosinophilic meningitis caused by the parasitic nematode Angiostrongylus cantonensis is an emerging infectious disease with recent outbreaks primarily in tropical and subtropical locations around the world, including Hawaii. Humans contract the disease primarily through ingestion of infected gastropods, the intermediate hosts of Angiostrongylus cantonensis. Effective prevention of the disease and control of the spread of the parasite require a thorough understanding of the parasite's hosts, including their distributions, as well as the human and environmental factors that contribute to transmission. The aim of this study was to screen a large cross section of gastropod species throughout the main Hawaiian Islands to determine which act as hosts of Angiostrongylus cantonensis and to assess the parasite loads in these species. Molecular screening of 7 native and 30 non-native gastropod species revealed the presence of the parasite in 16 species (2 native, 14 non-native). Four of the species tested are newly recorded hosts, two species introduced to Hawaii (Oxychilus alliarius, Cyclotropis sp.) and two native species (Philonesia sp., Tornatellides sp.). Those species testing positive were from a wide diversity of heterobranch taxa as well as two distantly related caenogastropod taxa. Review of the global literature showed that many gastropod species from 34 additional families can also act as hosts. There was a wide range of parasite loads among and within species, with an estimated maximum of 2.8 million larvae in one individual of Laevicaulis alte. This knowledge of the intermediate host range of Angiostrongylus cantonensis and the range of parasite loads will permit more focused efforts to detect, monitor and control the most important hosts, thereby improving disease prevention in Hawaii as well as globally.
Highlights
Angiostrongylus cantonensis is a parasitic nematode and one of the major causes of eosinophilic meningitis, a potentially fatal disease in humans and other mammals, as well as birds [1,2,3,4,5,6]
Non-native (n = 1,062) and native (n = 209) gastropod specimens were selected from these collections for screening to provide a broad coverage of species (37 species, 30 of them nonnative and 7 native) and locations (182 sites) (Figure 1), including in particular species previously recorded as carriers of A. cantonensis and those known to be widespread throughout the main Hawaiian Islands according to Cowie et al [32]
No specimens of four non-native species (Bradybaena similaris, Deroceras laeve, Limax flavus, Melanoides tuberculata) that have been recorded in other studies as hosts of A. cantonensis (Appendix S1) tested positive for the parasite
Summary
Angiostrongylus cantonensis is a parasitic nematode and one of the major causes of eosinophilic meningitis, a potentially fatal disease in humans and other mammals, as well as birds [1,2,3,4,5,6]. Definitive hosts of A. cantonensis include various rat species, mainly in the genus Rattus, which become infected by ingesting intermediate hosts (gastropods) or paratenic hosts (e.g. frogs, crabs, prawns, planarians) containing third stage A. cantonensis larvae [14,15,16,17,18]. These larvae mature fully and reproduce in the rat, resulting in eggs that hatch into first stage larvae. The ingested first stage larvae go through two molts to become third stage larvae while in the intermediate host, which is consumed by the definitive host and the cycle repeats [19]
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