title: Prevalence of Anaplasma phagocytophilum infection and effect on lamb growth.
abstract: BACKGROUND
  A major challenge in sheep farming during the grazing season along the coast of south-western Norway is tick-borne fever (TBF) caused by the bacteria Anaplasma phagocytophilum that is transmitted by the tick Ixodes ricinus.
  
  
  METHODS
  A study was carried out in 2007 and 2008 to examine the prevalence of A. phagocytophilum infection and effect on weaning weight in lambs. The study included 1208 lambs from farms in Sunndal Ram Circle in Møre and Romsdal County in Mid-Norway, where ticks are frequently observed. All lambs were blood sampled and serum was analyzed by an indirect fluorescent antibody assay (IFA) to determine an antibody status (positive or negative) to A. phagocytophilum infection. Weight and weight gain and possible effect of infection were analyzed using ANOVA and the MIXED procedure in SAS.
  
  
  RESULTS
  The overall prevalence of infection with A. phagocytophilum was 55%. A lower weaning weight of 3% (1.34 kg, p < 0.01) was estimated in lambs seropositive to an A. phagocytophilum infection compared to seronegative lambs at an average age of 137 days.
  
  
  CONCLUSIONS
  The results show that A. phagocytophilum infection has an effect on lamb weight gain. The study also support previous findings that A. phagocytophilum infection is widespread in areas where ticks are prevalent, even in flocks treated prophylactic with acaricides.
authors.affiliation: Organic Food and Farming Division, Norwegian Institute for Agricultural and Environmental Research (Bioforsk), Gunnars Veg 6, 6630 Tingvoll, Norway. lise.grova@bioforsk.no
authors.forename: Lise
authors.initials: L
authors.lastname: Grøva
authors.forename: Ingrid
authors.initials: I
authors.lastname: Olesen
authors.forename: Håvard
authors.initials: H
authors.lastname: Steinshamn
authors.forename: Snorre
authors.initials: S
authors.lastname: Stuen
mesh_terms: D041081:Anaplasma phagocytophilum / Q000276:immunology* / Q000302:isolation & purification*; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001835:Body Weight; D016873:Ehrlichiosis / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D005260:Female; D018884:Ixodes / Q000382:microbiology; D008297:Male; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D016036:Seroepidemiologic Studies; D012757:Sheep Diseases / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology*; D034561:Sheep, Domestic; D013984:Tick Infestations / Q000662:veterinary; D014886:Weaning
chemical_list: D000907:Antibodies, Bacterial