Abstract
Sequence analysis at the 35-fold-repetitive B1 locus identified three restriction sites capable of discriminating type I (mouse-virulent) from type II or III (mouse-avirulent) strains ofToxoplasma gondii. B1 PCR-restriction fragment length polymorphism analysis of 8 type I, 17 type II, and 8 type III strains confirms the specificity of the assay. It should now be possible to ask whether strain genotype affects the severity and type of clinical disease in humans.