Ultrastructure of Anaplasma marginale with an inclusion appendage, isolated in Minas Gerais State, Brazil.

This is the first report on the occurrence and isolation of a strain of Anaplasma marginale with an inclusion appendage in Brazil. The inclusion appendage presented longitudinal electron-dense striations and did not originate directly from the body of the rickettsia but from an electron-dense complex located at the junction of the inclusion membrane and inclusion appendage. The inclusion appendage remained in the host cell after the Anaplasma inclusion appeared to be leaving the red blood cell. Other ultrastructures of this rickettsia are described and its epidemiological importance is discussed.