In vivo isolation and maintenance of some wild strains of European hard tick spirochetes in mammalian and arthropod hosts. A parasitologist's view.

Methods and results of isolation and experimental maintenance of Borrelia strains from indigenous Ixodes ricinus ticks are described. Out of 12 different proved rodent species and breeding variants the mongolian jird or gerbils (Meriones unguiculatus) offers most perfectly all the necessary qualities to produce a transitory not progressive microscopically apparent spirochetemia when splenectomized previously. Using a laboratory breed of Ixodes ricinus the occurrence of transstadial and transovarial transmission could be confirmed in the vector tick. Each developmental stage of ticks can be infected via blood ingestion on spirochetemic mammalian hosts but each stage can infect vice versa its blood donors equally well. Needle borne transmissions from gerbil to gerbil by i.p. administration of infected blood are particularly successful after previous deep-freezing and cryopreservation of the blood samples or tissue suspensions. Attempts are described to infect other tick species than I. ricinus, fleas and mites, respectively, via blood meal. The problem of the spirochetes perfect adaptation to the host will be discussed.