Toxoplasma gondii infection in rats by the RH strain: inoculum and age effects

Toxoplasma gondii strains are classified according to their virulence in mice. Rats are considered to be resistant to the infection, depending on the age. Newborn rats are fully susceptible but weaned rats are resistant. However the effect of inoculum has not been examined. Using RH strain inocula of 10(2), 10(4), 5 x 10(7) and 10(8) tachyzoites intraperitoneally inoculated into Wistar and Fischer rats of 7, 11, 21, 24 and 46 days old, the authors show that inoculum and not the age of the host had a statistically significant effect (p < 0.01) on the survival curve.