title: Release of lungworm larvae from snails in the environment: potential for alternative transmission pathways.
abstract: BACKGROUND
  Gastropod-borne parasites may cause debilitating clinical conditions in animals and humans following the consumption of infected intermediate or paratenic hosts. However, the ingestion of fresh vegetables contaminated by snail mucus and/or water has also been proposed as a source of the infection for some zoonotic metastrongyloids (e.g., Angiostrongylus cantonensis). In the meantime, the feline lungworms Aelurostrongylus abstrusus and Troglostrongylus brevior are increasingly spreading among cat populations, along with their gastropod intermediate hosts. The aim of this study was to assess the potential of alternative transmission pathways for A. abstrusus and T. brevior L3 via the mucus of infected Helix aspersa snails and the water where gastropods died. In addition, the histological examination of snail specimens provided information on the larval localization and inflammatory reactions in the intermediate host.
  
  
  RESULTS
  Twenty-four specimens of H. aspersa received ~500 L1 of A. abstrusus and T. brevior, and were assigned to six study groups. Snails were subjected to different mechanical and chemical stimuli throughout 20 days in order to elicit the production of mucus. At the end of the study, gastropods were submerged in tap water and the sediment was observed for lungworm larvae for three consecutive days. Finally, snails were artificially digested and recovered larvae were counted and morphologically and molecularly identified. The anatomical localization of A. abstrusus and T. brevior larvae within snail tissues was investigated by histology. L3 were detected in the snail mucus (i.e., 37 A. abstrusus and 19 T. brevior) and in the sediment of submerged specimens (172 A. abstrusus and 39 T. brevior). Following the artificial digestion of H. aspersa snails, a mean number of 127.8 A. abstrusus and 60.3 T. brevior larvae were recovered. The number of snail sections positive for A. abstrusus was higher than those for T. brevior.
  
  
  CONCLUSIONS
  Results of this study indicate that A. abstrusus and T. brevior infective L3 are shed in the mucus of H. aspersa or in water where infected gastropods had died submerged. Both elimination pathways may represent alternative route(s) of environmental contamination and source of the infection for these nematodes under field conditions and may significantly affect the epidemiology of feline lungworms. Considering that snails may act as intermediate hosts for other metastrongyloid species, the environmental contamination by mucus-released larvae is discussed in a broader context.
authors.affiliation: Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy.
authors.forename: Alessio
authors.initials: A
authors.lastname: Giannelli
authors.affiliation: Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Colella
authors.affiliation: Department of Veterinary Science, University of Pisa, Pisa, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Abramo
authors.affiliation: Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy.
authors.forename: Rafael Antonio
authors.initials: RA
authors.lastname: do Nascimento Ramos
authors.affiliation: Department of Veterinary Science, University of Messina, Messina, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Falsone
authors.affiliation: Department of Veterinary Science, University of Messina, Messina, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Brianti
authors.affiliation: Department of Veterinary Medicine, University of Sassari, Sassari, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Varcasia
authors.affiliation: Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy; Department of Immunology, Aggeu Magalhães Research Institute, Oswaldo Cruz Foundation, Recife, Pernambuco, Brazil.
authors.forename: Filipe
authors.initials: F
authors.lastname: Dantas-Torres
authors.affiliation: Merial GmbH, Kathrinenhof Research Center, Rohrdorf, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Knaus
authors.affiliation: Department of Pathology and Pathogen Biology, The Royal Veterinary College, University of London, London, United Kingdom.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Fox
authors.affiliation: Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy.
authors.forename: Domenico
authors.initials: D
authors.lastname: Otranto
mesh_terms: D000818:Animals; D002371:Cat Diseases / Q000453:epidemiology* / Q000469:parasitology* / Q000635:transmission*; D002415:Cats; D005618:Fresh Water / Q000469:parasitology; D007814:Larva / Q000502:physiology; D008681:Metastrongyloidea / Q000502:physiology*; D009093:Mucus / Q000469:parasitology; D012908:Snails / Q000469:parasitology*; D017206:Strongylida Infections / Q000453:epidemiology / Q000635:transmission / Q000662:veterinary*