title: Distribution of Angiostrongylus vasorum and its gastropod intermediate hosts along the rural-urban gradient in two cities in the United Kingdom, using real time PCR.
abstract: BACKGROUND
  Angiostrongylus vasorum is a highly pathogenic metastrongylid nematode affecting dogs, which uses gastropod molluscs as intermediate hosts. The geographical distribution of the parasite appears to be heterogeneous or patchy and understanding of the factors underlying this heterogeneity is limited. In this study, we compared the species of gastropod present and the prevalence of A. vasorum along a rural-urban gradient in two cities in the south-west United Kingdom.
  
  
  METHODS
  The study was conducted in Swansea in south Wales (a known endemic hotspot for A. vasorum) and Bristol in south-west England (where reported cases are rare). In each location, slugs were sampled from nine sites across three broad habitat types (urban, suburban and rural). A total of 180 slugs were collected in Swansea in autumn 2012 and 338 in Bristol in summer 2014. A 10 mg sample of foot tissue was tested for the presence of A. vasorum by amplification of the second internal transcribed spacer (ITS-2) using a previously validated real-time PCR assay.
  
  
  RESULTS
  There was a significant difference in the prevalence of A. vasorum in slugs between cities: 29.4% in Swansea and 0.3% in Bristol. In Swansea, prevalence was higher in suburban than in rural and urban areas. Comparing the sampled slug fauna, Arion rufus was found in greater numbers in Swansea than Bristol, and was commonly infected (prevalence 41%). This, alongside the timing of slug collections in summer rather than autumn, could explain low infection prevalence in the Bristol sample. In the absence of Ar. rufus as a preferred host for A. vasorum, Ar. flagellus and Limacus maculatus appear to act as versatile hosts that are present in suburban and urban areas in Swansea (prevalence in Ar. flagellus 33%; in L. maculatus 44%) and in Bristol (prevalence in Ar. flagellus 0.9%). These slug species might provide A. vasorum with an alternative vehicle to reach the final host, when the main host Ar. rufus is scarce or absent.
  
  
  CONCLUSIONS
  We conclude that the composition of the slug fauna varies spatially, and that this could help explain patchiness in the prevalence of A. vasorum. A suburban peak was found in the prevalence of infection in intermediate hosts, perhaps explained by a higher density of competent intermediate and/or definitive hosts.
authors.affiliation: University of Bristol, Veterinary Parasitology & Ecology Group, School of Biological Sciences, Bristol Life Sciences Building, 24, Tyndall Avenue, Bristol, BS8 1TQ, UK. azlinaaziz@unisza.edu.my.|School of Animal Sciences, Faculty of Bioresources and Food Industry, Universiti Sultan Zainal Abidin, Kampus Tembila, 22200, Terengganu, Malaysia. azlinaaziz@unisza.edu.my.
authors.forename: Nor Azlina A
authors.initials: NA
authors.lastname: Aziz
authors.affiliation: University of Bristol, Veterinary Parasitology & Ecology Group, School of Biological Sciences, Bristol Life Sciences Building, 24, Tyndall Avenue, Bristol, BS8 1TQ, UK. ed13322.2013@my.bristol.ac.uk.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Daly
authors.affiliation: University of Bristol, Veterinary Parasitology & Ecology Group, School of Biological Sciences, Bristol Life Sciences Building, 24, Tyndall Avenue, Bristol, BS8 1TQ, UK. simon@gowerbirdhospital.org.uk.|Department of Biosciences, Swansea University, Singleton Park, Swansea, SA2 8PP, UK. simon@gowerbirdhospital.org.uk.
authors.forename: Simon
authors.initials: S
authors.lastname: Allen
authors.affiliation: Department of Natural Sciences, National Museum of Wales, Cardiff, Wales, CF10 3NP, UK. Ben.Rowson@museumwales.ac.uk.
authors.forename: Ben
authors.initials: B
authors.lastname: Rowson
authors.affiliation: Department of Biosciences, Swansea University, Singleton Park, Swansea, SA2 8PP, UK. C.Greig@swansea.ac.uk.
authors.forename: Carolyn
authors.initials: C
authors.lastname: Greig
authors.affiliation: Department of Biosciences, Swansea University, Singleton Park, Swansea, SA2 8PP, UK. d.w.forman@swansea.ac.uk.
authors.forename: Dan
authors.initials: D
authors.lastname: Forman
authors.affiliation: University of Bristol, Veterinary Parasitology & Ecology Group, School of Biological Sciences, Bristol Life Sciences Building, 24, Tyndall Avenue, Bristol, BS8 1TQ, UK. eric.morgan@bristol.ac.uk.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Morgan
mesh_terms: D000801:Angiostrongylus / Q000302:isolation & purification*; D000818:Animals; D002947:Cities / Q000453:epidemiology; D018509:DNA, Helminth / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D049851:Gastropoda / Q000469:parasitology*; D005843:Geography; D015995:Prevalence; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D018509:DNA, Helminth; D021903:DNA, Ribosomal Spacer
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