title: Loss of stages after continuous passage of Toxoplasma gondii and Besnoitia jellisoni.
abstract: Toxoplasma gondii, passed from mouse to mouse in the tachyzoite stage for 30-35 generations, developed cysts, which when fed to cats, failed to produce oocysts. Besnoitia jellisoni, passed similarly for 20 generations, lost the capacity to form cysts. These phenomena are explained by a loss of genomes or gene products during the rapid passage selecting for tachyzoites.
mesh_terms: D000818:Animals; D016782:Apicomplexa / Q000254:growth & development*; D002415:Cats; D051379:Mice; D011528:Protozoan Infections / Q000469:parasitology*; D014122:Toxoplasma / Q000254:growth & development*; D014123:Toxoplasmosis / Q000469:parasitology*