title: Transmission of Calicophoron daubneyi and Fasciola hepatica in Galicia (Spain): Temporal follow-up in the intermediate and definitive hosts.
abstract: Paramphistomosis caused by Calicophoron daubneyi and fasciolosis caused by Fasciola hepatica are common parasitic diseases of livestock animals. Transmission of the diseases depends on the presence of intermediate hosts, i.e. freshwater gastropods such as lymnaeids. We carried out a 2-year-long study of the dynamics of the snail population acting as the intermediate host for these parasites, considering the population structure in terms of size/age and infection status. In addition, we determined the kinetics of trematode egg excretion in grazing cows. Generalized Additive Models (GAMs) were used to analyze the associations between different response variables and snail size, sampling month and weather-related variables.
  
  
  
  Of the molluscan species examined, Galba truncatula, Radix peregra, Anisus (Anisus) leucostoma and Pisidium casertanum (n = 2802), only G. truncatula was infected with C. daubneyi or F. hepatica, at prevalence rates of 8.2% and 4.4% respectively. The probability of infection with C. daubneyi or F. hepatica was linearly related to snail size, although in different ways (negative for C. daubneyi and positive for F. hepatica). The total snail population increased in winter, when specimens of all size classes were found. Infected snails were more abundant during spring-autumn. Mature cercariae of both parasites were found in most seasons. In the statistical models, the sampling month accounted for a high percentage (71.9-78.2%) of the observed variability in snail abundance. The inclusion of climatic variables in the models moderately increased the percentage of deviance explained (77.7-91.9%). Excretion of C. daubneyi eggs in cow faeces was always higher than that of F. hepatica eggs.
  
  
  
  Particular care should be taken to prevent pastures and the surrounding environment being contaminated with parasite eggs during winter-spring, when the number of snails susceptible to miracidial infections is maximal. This is therefore the optimal time for treating grazing animals. Nevertheless, control of trematodosis based only on chemotherapy is difficult in an area such as the study area, where environmental factors favour the regular appearance of snail populations harbouring mature cercariae.
authors.affiliation: Departamento de Zooloxía, Xenética e Antropoloxía Física, Facultade de Bioloxía, Campus Vida, Universidade de Santiago de Compostela, 15706, Santiago de Compostela (A Coruña), Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Iglesias-Piñeiro
authors.affiliation: Laboratorio de Parasitología, Centro de Investigaciones Agrarias de Mabegondo, Instituto Galego de Calidade Alimentaria-Xunta de Galicia, Carretera AC-542 de Betanzos a Mesón do Vento, Km 7, 15318, Abegondo (A Coruña), Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: González-Warleta
authors.affiliation: Laboratorio de Parasitología, Centro de Investigaciones Agrarias de Mabegondo, Instituto Galego de Calidade Alimentaria-Xunta de Galicia, Carretera AC-542 de Betanzos a Mesón do Vento, Km 7, 15318, Abegondo (A Coruña), Spain.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Castro-Hermida
authors.affiliation: Department of Crop and Soil Science, Oregon State University, Corvallis, OR, 97331, USA.
authors.forename: María
authors.initials: M
authors.lastname: Córdoba
authors.affiliation: Departamento de Sanidad Animal, Instituto de Ganadería de Montaña, Consejo Superior de Investigaciones Científicas (CSIC)-ULE, 24346, Grulleros (León), Spain.
authors.forename: Camino
authors.initials: C
authors.lastname: González-Lanza
authors.affiliation: Departamento de Sanidad Animal, Instituto de Ganadería de Montaña, Consejo Superior de Investigaciones Científicas (CSIC)-ULE, 24346, Grulleros (León), Spain.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Manga-González
authors.affiliation: Laboratorio de Parasitología, Centro de Investigaciones Agrarias de Mabegondo, Instituto Galego de Calidade Alimentaria-Xunta de Galicia, Carretera AC-542 de Betanzos a Mesón do Vento, Km 7, 15318, Abegondo (A Coruña), Spain. mercedes.mezo.menendez@xunta.es.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Mezo
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology*; D010270:Parasite Egg Count; D015995:Prevalence; D012908:Snails / Q000469:parasitology*; D013030:Spain / Q000453:epidemiology; D014200:Trematoda / Q000145:classification / Q000302:isolation & purification*; D014201:Trematode Infections / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*
keywords: Calicophoron daubneyi; Fasciola hepatica; GAM; Galba truncatula; Seasonal trends; Snail hosts