The Prevalence of Angiostrongylus cantonensis/mackerrasae Complex in Molluscs from the Sydney Region.

John Harkness,Richard Malik,Douglas Chan,Michael Shea,Malcolm Jones,Henk D F H Schallig,Joel Barratt,Tamalee Roberts,Rogan Lee,Deborah Marriott,Mahdis Aghazadeh,Damien Stark,John Ellis

doi:10.1371/journal.pone.0128128

Abstract

Angiostrongylus cantonensis and Angiostrongylus mackerrasae are metastrongyloid nematodes that infect various rat species. Terrestrial and aquatic molluscs are intermediate hosts of these worms while humans and dogs are accidental hosts. Angiostrongylus cantonensis is the major cause of angiostrongyliasis, a disease characterised by eosinophilic meningitis. Although both A. cantonensis and A. mackerrasae are found in Australia, A. cantonensis appears to account for most infections in humans and animals. Due to the occurrence of several severe clinical cases in Sydney and Brisbane, the need for epidemiological studies on angiostrongyliasis in this region has become apparent. In the present study, a conventional PCR and a TaqMan assay were compared for their ability to amplify Angiostrongylus DNA from DNA extracted from molluscs. The TaqMan assay was more sensitive, capable of detecting the DNA equivalent to one hundredth of a nematode larva. Therefore, the TaqMan assay was used to screen molluscs (n=500) of 14 species collected from the Sydney region. Angiostrongylus DNA was detected in 2 of the 14 mollusc species; Cornu aspersum [14/312 (4.5%)], and Bradybaenia similaris [1/10 (10%)], which are non-native terrestrial snails commonly found in urban habitats. The prevalence of Angiostrongylus spp. was 3.0% ± 0.8% (CI 95%). Additionally, experimentally infected Austropeplea lessoni snails shed A. cantonensis larvae in their mucus, implicating mucus as a source of infection. This is the first Australian study to survey molluscs using real-time PCR and confirms that the garden snail, C. aspersum, is a common intermediate host for Angiostrongylus spp. in Sydney.

Highlights

Angiostrongylus cantonensis and Angiostrongylus mackerrasae are metastrongyloid nematodes that infect various rat species
After plotting the standard curve, the TaqMan real-time PCR efficiency was calculated to be 106.5% and with an R2 value of 0.996. Both PCR assays amplified products from A. mackerrasae as well as A. cantonensis but did not amplify products for DNA extracted from the other helminths tested
Angiostrongyliasis is a rare disease in humans caused by the rat lungworm (A. cantonensis)

Summary

Introduction

Angiostrongylus cantonensis and Angiostrongylus mackerrasae are metastrongyloid nematodes that infect various rat species. A conventional PCR assay was developed by the Centers for Disease Control and Prevention (CDC) to survey local mollusc populations in the Hawaiian Islands, in response to a local outbreak of A. cantonensis infection [15] This assay detects approximately one Angiostrongylus larva per milligram of mollusc tissue, cross reaction with DNA from another strongylid worm was reported [15]. These cases highlight the need to generate new epidemiological data for angiostrongyliasis in this region To address this issue and facilitate an assessment of the potential risk of angiostrongyliasis in this region, this study compared the conventional PCR and TaqMan. assay developed by Qvarnstrom et al [15,16] for their ability to amplify Angiostrongylus DNA in DNA extracted from mollusc tissues collected throughout NSW but focussed on the Sydney area

Ethics statement

Results

Discussion