However, in vitro cultures have shown that 21 weeks after infection 50% (3 out of 6), 66.7% (2 out of 3) and 16.7% (1 out of 6) spleens of female mice of the strains CcS-3, -18 and -20, respectively, contained viable parasites. The gene discussed is EEF1A1; the disease is infection.