Virulence parameters obtained in Swiss mice from <i>Trypanosoma cruzi</i> I and IV strains.

aCumulative mortality from inoculation until the 90th day after inoculation (d.a.i); bCumulative mortality from the 90th until the 180th d.a.i.; cPercentage of animals presenting positive fresh blood examination within the first two months following inoculation and/or positive hemoculture and/or PCR on the 55th d.a.i.; dPercentage of animals presenting positive ELISA in the 115th d.a.i.; ePercentage of animals presenting positive ELISA in the 205th d.a.i.. fp<0.05: significant difference; N.S.: not significant.