title: Genetic variants of Anaplasma phagocytophilum from 14 equine granulocytic anaplasmosis cases.
abstract: BACKGROUND
  Equine Granulocytic Anaplasmosis (EGA) is caused by Anaplasma phagocytophilum, a tick-transmitted, obligate intracellular bacterium. In Europe, it is transmitted by Ixodes ricinus. A large number of genetic variants of A. phagocytophilum circulate in nature and have been found in ticks and different animals. Attempts have been made to assign certain genetic variants to certain host species or pathologies, but have not been successful so far. The purpose of this study was to investigate the causing agent A. phagocytophilum of 14 cases of EGA in naturally infected horses with molecular methods on the basis of 4 partial genes (16S rRNA, groEL, msp2, and msp4).
  
  
  RESULTS
  All DNA extracts of EDTA-blood samples of the horses gave bands of the correct nucleotide size in all four genotyping PCRs. Sequence analysis revealed 4 different variants in the partial 16S rRNA, groEL gene and msp2 genes, and 3 in the msp4 gene. One 16S rRNA gene variant involved in 11 of the 14 cases was identical to the "prototype" variant causing disease in humans in the amplified part [GenBank: U02521]. Phylogenetic analysis revealed as expected for the groEL gene that sequences from horses clustered separately from roe deer. Sequences of the partial msp2 gene from this study formed a separate cluster from ruminant variants in Europe and from all US variants.
  
  
  CONCLUSIONS
  The results show that more than one variant of A. phagocytophilum seems to be involved in EGA in Germany. The comparative genetic analysis of the variants involved points towards different natural cycles in the epidemiology of A. phagocytophilum, possibly involving different reservoir hosts or host adaptation, rather than a strict species separation.
authors.affiliation: Comparative Tropical Medicine and Parasitology, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität, Leopoldstr, 5, 80802 Munich, Germany. cornelia.silaghi@tropa.vetmed.uni-muenchen.de
authors.forename: Cornelia
authors.initials: C
authors.lastname: Silaghi
authors.forename: Gabriele
authors.initials: G
authors.lastname: Liebisch
authors.forename: Kurt
authors.initials: K
authors.lastname: Pfister
mesh_terms: D041081:Anaplasma phagocytophilum / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D000712:Anaplasmosis / Q000382:microbiology*; D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D018834:Chaperonin 60 / Q000235:genetics; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005858:Germany; D006734:Horse Diseases / Q000382:microbiology*; D006736:Horses; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D001425:Bacterial Outer Membrane Proteins; D018834:Chaperonin 60; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; C450839:p44 protein, Anaplasma phagocytophila