title: A comparative study of clinical manifestations, haematological and serological responses after experimental infection with Anaplasma phagocytophilum in two Norwegian sheep breeds.
abstract: BACKGROUND
  It has been questioned if the old native Norwegian sheep breed, Old Norse Sheep (also called Norwegian Feral Sheep), normally distributed on coastal areas where ticks are abundant, is more protected against tick-borne infections than other Norwegian breeds due to a continuously high selection pressure on pasture. The aim of the present study was to test this hypothesis in an experimental infection study.
  
  
  METHODS
  Five-months-old lambs of two Norwegian sheep breeds, Norwegian White (NW) sheep and Old Norse (ON) sheep, were experimentally infected with a 16S rRNA genetic variant of Anaplasma phagocytophilum (similar to GenBank accession number M73220). The experiment was repeated for two subsequent years, 2008 and 2009, with the use of 16 lambs of each breed annually. Ten lambs of each breed were inoculated intravenously each year with 0.4 ml A. phagocytophilum-infected blood containing approximately 0.5 × 106 infected neutrophils/ml. Six lambs of each breed were used as uninfected controls. Half of the primary inoculated lambs in each breed were re-challenged with the same infectious dose at nine (2008) and twelve (2009) weeks after the first challenge. The clinical, haematological and serological responses to A. phagocytophilum infection were compared in the two sheep breeds.
  
  
  RESULTS
  The present study indicates a difference in fever response and infection rate between breeds of Norwegian sheep after experimental infection with A. phagocytophilum.
  
  
  CONCLUSIONS
  Although clinical response seems to be less in ON-lambs compared to NW-lambs, further studies including more animals are needed to evaluate if the ON-breed is more protected against tick-borne infections than other Norwegian breeds.
authors.affiliation: Department of Production Animal Clinical Sciences, Norwegian School of Veterinary Science, Sandnes, Norway. snorre.stuen@nvh.no
authors.forename: Snorre
authors.initials: S
authors.lastname: Stuen
authors.forename: Lise
authors.initials: L
authors.lastname: Grøva
authors.forename: Erik G
authors.initials: EG
authors.lastname: Granquist
authors.forename: Karin
authors.initials: K
authors.lastname: Sandstedt
authors.forename: Ingrid
authors.initials: I
authors.lastname: Olesen
authors.forename: Håvard
authors.initials: H
authors.lastname: Steinshamn
mesh_terms: D041081:Anaplasma phagocytophilum; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D016873:Ehrlichiosis / Q000235:genetics / Q000276:immunology / Q000382:microbiology / Q000662:veterinary*; D020022:Genetic Predisposition to Disease; D012756:Sheep; D012757:Sheep Diseases / Q000235:genetics / Q000276:immunology / Q000382:microbiology*; D015430:Weight Gain
chemical_list: D000907:Antibodies, Bacterial