Toxoplasma gondii

Rêgo, W. M. F., Costa, J. G. L., Baraviera, R. C. A., Pinto, L. V., Bessa, G. L., Lopes, R. E. N., Silveira, J. A. G. & Vitor, R. W. A., 2018, Genetic diversity of Toxoplasma gondii isolates obtained from free-living wild birds rescued in Southeastern Brazil, International Journal for Parasitology: Parasites and Wildlife 7 (3), pp. 432-438 : 434

2.6. Virulence of new isolates of T. gondii in mice

The virulence of the new isolates of T. gondii was determined according to Ferreira et al. (2001) in a total of 180 BALB/c female mice. Five mice were i.p. Inoculated with 1, 10, 100 and 1000 tachyzoites of each isolate in 0.2 mL of PBS (pH 7.2). Five animals inoculated with 0.2 mL of PBS (pH 7.2) were maintained as negative controls. For comparison, five mice were inoculated with tachyzoites of RH (lethal) and five with ME49 (nonlethal) strains, as references. Mice mortality was observed over a 30-day period. The survivors were tested by ELISA. Mice that were inoculated but not seroconverted according to ELISA were excluded from the experiment. All ELISA-positive surviving mice were euthanized to look for tissue cysts in the brain. Isolates killing 100% of the infected mice were classified as virulent. Isolates with LD 100 greater than 1000 tachyzoites were classified as avirulent, and those with an intermediate pattern between the two extremes were classified as having intermediate virulence ( Howe and Sibley, 1995).