title: Persistence of Anaplasma ovis infection and conservation of the msp-2 and msp-3 multigene families within the genus Anaplasma.
abstract: Goats which have recovered from acute Anaplasma ovis infection remain seropositive, although infected erythrocytes cannot be detected by microscopic examination. Persistence of A. ovis 17 to 21 months following experimental infection was demonstrated by PCR detection of the msp-5 gene. Quantitative analysis of persistent rickettsemia over time showed that all levels were below the limit of microscopic detection and ranged from a low of 10(2) organisms/ml to peaks of 10(6) organisms/ml. Two patterns of persistent rickettsemia were observed: the first was characterized by cyclic fluctuations at 6- to 9-week intervals, similar to the pattern described for A. marginale-infected cattle, while in the second pattern, repetitive cycles did not occur and the rickettsemia levels were relatively constant. The msp-2 and msp-3 multigene families, which provide the genetic capacity for outer membrane protein antigenic variation during persistent A. marginale rickettsemia, were identified in the A. ovis genome by Southern blot analysis, and expression of an MSP-2 homologue was confirmed by using immunoblots.
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA. gpalmer@vetmed.wsu.edu
authors.forename: G H
authors.initials: GH
authors.lastname: Palmer
authors.forename: J R
authors.initials: JR
authors.lastname: Abbott
authors.forename: D M
authors.initials: DM
authors.lastname: French
authors.forename: T F
authors.initials: TF
authors.lastname: McElwain
mesh_terms: D000709:Anaplasma / Q000235:genetics*; D000712:Anaplasmosis / Q000097:blood*; D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics*; D016470:Bacteremia; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000235:genetics; D002908:Chronic Disease; D018628:Gene Dosage; D005798:Genes, Bacterial; D015511:Goat Diseases / Q000097:blood*; D006041:Goats; D005810:Multigene Family; D016133:Polymerase Chain Reaction
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; C103346:major surface protein 3, Anaplasma marginale; C103348:msp2 protein, Anaplasma marginale