In the Central European conditions, three species of Babesia have epidemiological significance as human pathogens – Babesia divergens, B. microti and B. venatorum. Tick Ixodes ricinus is considered as their main vector, wild mammals as the animal reservoir. The zoonotic cycles of small and large Babesia differ in details. Due to the lack of transovarial mode transmission in small species B. microti, the circulation goes mainly between immature ticks and vertebrate hosts; pathogen circulates primarily in the cycle: infected rodent → the tick larva → the nymph → the mammal reservoir →the larva of the tick. The tick stages able to effectively infect human are nymphs and adult females, males do not participate in the follow transmission. For large Babesia – B. divergens and B. venatorum, the transovarial and transstadial transmission enable the presence of the agent in adult ticks, moreover, that larvae and nymphs feed on not-susceptible hosts. The tick stages able to effectively infect cattle and other ruminants are adult females. Resuming, pathogen circulates primarily in the cycle the ruminant host – adult female tick – the larva – the nymph – adult female of the next generation – the ruminant. Due to the compound developmental transmission has place after the outflow of a tick began feeding.