title: A morphological and molecular study of Anaplasma phagocytophilum transmission events at the time of Ixodes ricinus tick bite.
abstract: BACKGROUND
  Anaplasma phagocytophilum is the causative agent of human granulocytic anaplasmosis (HGA) in humans and tick-borne fever (TBF) in ruminants. The bacterium invades and replicates in phagocytes, especially in polymorphonuclear granulocytes.
  
  
  METHODS
  In the present study, skin biopsies and ticks (Ixodes ricinus) were collected from tick feeding lesions on 38 grazing lambs between two and three weeks after access to pastures. The histopathological changes associated with tick bites and A. phagocytophilum infection, were described. In addition the skin biopsies were examined by immunohistochemistry. Furthermore, samples from blood, skin biopsies and ticks were examined by serology, PCR amplification of msp2 (p44), genotyping of rrs (16S rRNA) variants, and compared with the results obtained from histological and immunohistochemical investigations.
  
  
  RESULTS
  Tick bites were associated with chronic and hyperplastic inflammatory skin lesions in this study. A. phagocytophilum present in skin lesions were mainly associated with neutrophils and macrophages. Bacteria were occasionally observed in the Tunica media and Tunica adventitia of small vessels, but were rarely found in association with endothelial cells. PCR and genotyping of organisms present in blood, ticks and skin biopsies suggested a haematogenous and a local spread of organisms at the tick attachment sites.
  
  
  CONCLUSIONS
  The present study describes different aspects of A. phagocytophilum infection at the site of tick bite, and indicates that A. phagocytophilum rarely associates with endothelium during the early pathogenesis of infection.
authors.affiliation: Department of Production Animal Clinical Sciences, Section of Small Ruminant Research, Norwegian School of Veterinary Science, Sandnes, N-4325 Norway. erikgeorg.granquist@veths.no
authors.forename: Erik G
authors.initials: EG
authors.lastname: Granquist
authors.forename: Mona
authors.initials: M
authors.lastname: Aleksandersen
authors.forename: Karin
authors.initials: K
authors.lastname: Bergström
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Dumler
authors.forename: Wenche O
authors.initials: WO
authors.lastname: Torsteinbø
authors.forename: Snorre
authors.initials: S
authors.lastname: Stuen
mesh_terms: D041081:Anaplasma phagocytophilum / Q000235:genetics / Q000302:isolation & purification*; D000712:Anaplasmosis / Q000097:blood / Q000382:microbiology* / Q000635:transmission; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics; D001706:Biopsy / Q000662:veterinary; D001733:Bites and Stings / Q000662:veterinary*; D001772:Blood Cell Count; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D007150:Immunohistochemistry / Q000662:veterinary; D018884:Ixodes / Q000382:microbiology*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology* / Q000469:parasitology* / Q000635:transmission; D017282:Tick-Borne Diseases / Q000097:blood / Q000382:microbiology / Q000635:transmission / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; C488283:msp2 protein, Anaplasma phagocytophilum