title: Epidemiology and impact of Fasciola hepatica exposure in high-yielding dairy herds.
abstract: The liver fluke Fasciola hepatica is a trematode parasite with a worldwide distribution and is the cause of important production losses in the dairy industry. The aim of this observational study was to assess the prevalence of exposure to F. hepatica in a group of high yielding dairy herds, to determine the risk factors and investigate their associations with production and fertility parameters. Bulk milk tank samples from 606 herds that supply a single retailer with liquid milk were tested with an antibody ELISA for F. hepatica. Multivariable linear regression was used to investigate the effect of farm management and environmental risk factors on F. hepatica exposure. Higher rainfall, grazing boggy pasture, presence of beef cattle on farm, access to a stream or pond and smaller herd size were associated with an increased risk of exposure. Univariable regression was used to look for associations between fluke exposure and production-related variables including milk yield, composition, somatic cell count and calving index. Although causation cannot be assumed, a significant (p<0.001) negative association was seen between F. hepatica exposure and estimated milk yield at the herd level, representing a 15% decrease in yield for an increase in F. hepatica exposure from the 25th to the 75th percentile. This remained significant when fertility, farm management and environmental factors were controlled for. No associations were found between F. hepatica exposure and any of the other production, disease or fertility variables.
authors.affiliation: Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool, L69 7ZJ, UK; School of Veterinary Science, University of Liverpool, Leahurst, Chester High Road, Neston, CH64 7TE, UK. Electronic address: alison.howell@liv.ac.uk.
authors.forename: Alison
authors.initials: A
authors.lastname: Howell
authors.affiliation: NIHR Health protection Research Unit in Emerging and Zoonotic Infections, Institute of Infection and Global Health, University of Liverpool, L69 7BE, UK; Department of Epidemiology and Population Health, Institute of Infection and Global Health, Leahurst, Chester High Road, Neston, CH64 7TE, UK.
authors.forename: Matthew
authors.initials: M
authors.lastname: Baylis
authors.affiliation: School of Veterinary Science, University of Liverpool, Leahurst, Chester High Road, Neston, CH64 7TE, UK.
authors.forename: Rob
authors.initials: R
authors.lastname: Smith
authors.affiliation: Department of Epidemiology and Population Health, Institute of Infection and Global Health, Leahurst, Chester High Road, Neston, CH64 7TE, UK; School of Veterinary Science, University of Liverpool, Leahurst, Chester High Road, Neston, CH64 7TE, UK.
authors.forename: Gina
authors.initials: G
authors.lastname: Pinchbeck
authors.affiliation: Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Liverpool, L69 7ZJ, UK; School of Veterinary Science, University of Liverpool, Leahurst, Chester High Road, Neston, CH64 7TE, UK.
authors.forename: Diana
authors.initials: D
authors.lastname: Williams
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000032:analysis; D002417:Cattle; D002418:Cattle Diseases / Q000191:economics* / Q000453:epidemiology* / Q000469:parasitology; D002980:Climate; D003612:Dairying / Q000379:methods*; D004739:England / Q000453:epidemiology; D004777:Environment; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005210:Fasciola hepatica / Q000302:isolation & purification; D005211:Fascioliasis / Q000191:economics* / Q000453:epidemiology* / Q000469:parasitology; D005260:Female; D007774:Lactation; D008892:Milk / Q000378:metabolism; D015995:Prevalence; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology; D014852:Wales / Q000453:epidemiology
chemical_list: D000909:Antibodies, Helminth
keywords: Dairy cattle; Fasciola hepatica; Milk production; Risk factors