3.6 Pathogenicity in chickens and mice
All chickens in both groups died within two days after intravenously inoculated with 100 μl tenfold diluted viruses, and the values of IVPI were 2.92 (BJ3426) and 2.84 (SX1616), respectively (Table 3), indicating that both strains were highly pathogenic to chickens.
Next, we evaluated the biological characteristics and pathogenicity of these two strains in BALB/c mice. As shown in Figure 4, no deaths were observed during the two-week’s observation. Furthermore, body weight measurement revealed that mice inoculated with both viruses only experienced a transient infection at the dose of 106.5EID50 on 4-5 days post infection during the experiment. Based on the 50% mouse lethal dose (MLD50) (Table 3) and percent survival curves, we drew the conclusion that these two H7N9 viruses were low virulent to mice.