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Infection and Immunity, December 1998, p. 6035-6039, Vol. 66, No. 12
Department of Veterinary Microbiology and
Pathology, Washington State University, Pullman, Washington
99164-7040
Received 15 June 1998/Returned for modification 17 August
1998/Accepted 2 September 1998
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 102 organisms/ml to peaks of
106 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.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Persistence of Anaplasma ovis Infection
and Conservation of the msp-2 and msp-3 Multigene
Families within the Genus Anaplasma
*
Corresponding author. Mailing address: Department of
Veterinary Microbiology and Pathology, Washington State University,
Pullman, WA 99164-7040. Phone: (509) 335-6033. Fax: (509) 335-8328. E-mail: gpalmer{at}vetmed.wsu.edu.
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