Figure 3.

Tick molecules involved in Anaplasma transmission. Schematic diagram representing general stages of Anaplasma infection and transmission (Kocan et al., 2008a). Tick genes, for which interference with Anaplasma acquisition and/or transmission have been proved by genetic tests, are shown in rectangles (see text and the Table 2 for their function and references). Infected red blood cells (neutrophils for A. phagocytophilum) are engorged by the tick during blood meal. The released bacteria infect tick midgut cells and develop reticulate (cell-dividing; open circle) and dense core (infective; filled circle) forms of colonies inside the cells. During the next feeding, bacteria are released from the cells and infect other tissues including salivary glands. Here, they multiply inside the cells and are released into the saliva and transferred into the new host. Infection of tick hemocytes is required for the pathogen migration from the midgut to the salivary glands (Liu et al., 2011). Transovarial transmission of Anaplasma does not seem to occur. Transmission in one-host ticks is probably accompanied by tick males, which can feed repeatedly and transfer between hosts.