title: Longitudinal study on the temporal and micro-spatial distribution of Galba truncatula in four farms in Belgium as a base for small-scale risk mapping of Fasciola hepatica.
abstract: BACKGROUND
  The trematode parasite Fasciola hepatica causes important economic losses in ruminants worldwide. Current spatial distribution models do not provide sufficient detail to support farm-specific control strategies. A technology to reliably assess the spatial distribution of intermediate host snail habitats on farms would be a major step forward to this respect. The aim of this study was to conduct a longitudinal field survey in Flanders (Belgium) to (i) characterise suitable small water bodies (SWB) for Galba truncatula and (ii) describe the population dynamics of G. truncatula.
  
  
  METHODS
  Four F. hepatica-infected farms from two distinct agricultural regions were examined for the abundance of G. truncatula from the beginning (April 2012) until the end (November 2012) of the grazing season. Per farm, 12 to 18 SWB were selected for monthly examination, using a 10 m transect analysis. Observations on G. truncatula abundance were coupled with meteorological and (micro-)environmental factors and the within-herd prevalence of F. hepatica using simple comparison or negative binomial regression models.
  
  
  RESULTS
  A total of 54 examined SWB were classified as a pond, ditch, trench, furrow or moist area. G. truncatula abundance was significantly associated with SWB-type, region and total monthly precipitation, but not with monthly temperature. The clear differences in G. truncatula abundance between the 2 studied regions did not result in comparable differences in F. hepatica prevalence in the cattle. Exploration of the relationship of G. truncatula abundance with (micro)-environmental variables revealed a positive association with soil and water pH and the occurrence of Ranunculus sp. and a negative association with mowed pastures, water temperature and presence of reed-like plant species.
  
  
  CONCLUSIONS
  Farm-level predictions of G. truncatula risk and subsequent risk for F. hepatica occurrence would require a rainfall, soil type (representing the agricultural region) and SWB layer in a geographic information system. While rainfall and soil type information is easily accessible, the recent advances in very high spatial resolution cameras carried on board of satellites, planes or drones should allow the delineation of SWBs in the future.
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium. johannes.charlier@ugent.be.
authors.forename: Johannes
authors.initials: J
authors.lastname: Charlier
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium. karensoenen@hotmail.com.
authors.forename: Karen
authors.initials: K
authors.lastname: Soenen
authors.affiliation: Laboratory of Forest Management and Spatial Information Techniques, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium. els.dr@hotmail.com.
authors.forename: Els
authors.initials: E
authors.lastname: De Roeck
authors.affiliation: Avia-GIS, Risschotlei 33, 2980, Zoersel, Belgium. whantson@avia-gis.com.
authors.forename: Wouter
authors.initials: W
authors.lastname: Hantson
authors.affiliation: Avia-GIS, Risschotlei 33, 2980, Zoersel, Belgium. educheyne@avia-gis.com.
authors.forename: Els
authors.initials: E
authors.lastname: Ducheyne
authors.affiliation: Laboratory of Forest Management and Spatial Information Techniques, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium. frieke.vancoillie@UGent.be.
authors.forename: Frieke
authors.initials: F
authors.lastname: Van Coillie
authors.affiliation: Laboratory of Forest Management and Spatial Information Techniques, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, 9000, Gent, Belgium. robert.dewulf@ugent.be.
authors.forename: Robert
authors.initials: R
authors.lastname: De Wulf
authors.affiliation: Avia-GIS, Risschotlei 33, 2980, Zoersel, Belgium. ghendrickx@avia-gis.com.
authors.forename: Guy
authors.initials: G
authors.lastname: Hendrickx
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820, Merelbeke, Belgium. jozef.vercruysse@ugent.be.
authors.forename: Jozef
authors.initials: J
authors.lastname: Vercruysse
mesh_terms: D000818:Animals; D001530:Belgium / Q000453:epidemiology; D005210:Fasciola hepatica; D005211:Fascioliasis / Q000453:epidemiology; D011891:Rain; D012307:Risk Factors; D012908:Snails / Q000469:parasitology* / Q000502:physiology*; D013997:Time Factors