Dreher, U. M. de la Fuente, J. Hofmann-Lehmann, R. Meli, M. L. Pusterla, N. Kocan, K. M. Woldehiwet, Z. Braun, U. Regula, G. Staerk, K. D. C. Lutz, H. <jats:title>ABSTRACT</jats:title> <jats:p>In the context of a serosurvey conducted on the <jats:italic>Anaplasma marginale</jats:italic> prevalence in Swiss cattle, we suspected that a serological cross-reactivity between <jats:italic>A. marginale</jats:italic> and <jats:italic>A. phagocytophilum</jats:italic> might exist. In the present study we demonstrate that cattle, sheep and horses experimentally infected with <jats:italic>A. phagocytophilum</jats:italic> not only develop antibodies to <jats:italic>A. phagocytophilum</jats:italic> (detected by immunofluorescent-antibody assay) but also to <jats:italic>A. marginale</jats:italic> (detected by a competitive enzyme-linked immunosorbent assay). Conversely, calves experimentally infected with <jats:italic>A. marginale</jats:italic> also developed antibodies to <jats:italic>A. phagocytophilum</jats:italic> using the same serological tests. The identity of 63% determined in silico within a 209-amino-acid sequence of major surface protein 5 of an isolate of <jats:italic>A. marginale</jats:italic> and one of <jats:italic>A. phagocytophilum</jats:italic> supported the observed immunological cross-reactivity. These observations have important consequences for the serotesting of both, <jats:italic>A. marginale</jats:italic> and <jats:italic>A. phagocytophilum</jats:italic> infection of several animal species. In view of these new findings, tests that have been considered specific for either infection must be interpreted carefully.</jats:p> application/pdf https://sonar.ch/global/documents/164499 eng info:eu-repo/semantics/altIdentifier/doi/10.1128/cdli.12.10.1177-1183.2005 info:eu-repo/semantics/altIdentifier/issn/1071-412X info:eu-repo/semantics/openAccess Clinical Diagnostic Laboratory Immunology. - American Society for Microbiology. - 2005, vol. 12, no. 10, p. 1177-1183 Immunology Immunology and Allergy Microbiology (medical) Clinical Biochemistry Serologic Cross-Reactivity between Anaplasma marginale and Anaplasma phagocytophilum http://purl.org/coar/resource_type/c_6501