Schematic of the development cycle of A. marginale in cattle and ticks. Schematic of the development cycle of A. marginale in cattle and ticks. Infected erythrocytes are ingested by ticks (Dermacentor spp., Rhipicephalus spp., or Boophilus spp.) with the blood meal. The first site of infection of A. marginale in ticks is the gut cells. When the ticks feed a second time, many tick tissues become infected, including salivary gland cells, from where the rickettsia is transmitted back to cattle. Two forms of A. marginale, reticulated and dense forms, are found in infected tick cells. Reticulated forms appear first and are the vegetative stage that divides by binary fission. The reticulated form changes into the dense form, which is the infective form and can survive extracellularly. (Reprinted from reference 125 with permission from the publisher.)‏ Katherine M. Kocan et al. Clin. Microbiol. Rev. 2003; doi:10.1128/CMR.16.4.698-712.2003