Table 1. Virulence of recombinant H5N1 viruses in chickens after intranasal inoculation.
| Virus | Inoculated chickens | Contact chickens | |||
|---|---|---|---|---|---|
| Mortality | PI | MTD | Mortality | MTD | |
| rg-AL | 6/6 | 2.5 | 2 days | 4/4 | 4.5 days |
| rg-HL-08 | 6/6 | 2.5 | 2 days | 4/4 | 4.0 days |
| rg-HL-16 | 6/6 | 2.4 | 2 days | 4/4 | 5.0 days |
| rg-AL-46D | 6/6 | 2.4 | 3 days | 4/4 | 4.5 days |
| rg-AL-204M | 6/6 | 2.3 | 3 days | 4/4 | 5.0 days |
| rg-AL-319F | 6/6 | 2.3 | 3 days | 4/4 | 5.0 days |
| rg-AL-430G | 6/6 | 2.4 | 2.8 days | 4/4 | 5.0 days |
Chickens were inoculated intranasal with 104 PFU/bird and one-day post infection (dpi) naïve chickens were added to each group to assess virus transmission.
PI = pathogenicity index; it was calculated as mean value of daily clinical scoring of animals as 0 (healthy), 1 (showing one clinical sign: depression, cyanosis of shanks, comb and wattles, respiratory distress, diarrhoea), 2 (showing two clinical signs) and 3 (dead) for 10 days according to the OIE guidelines. MTD = mean time to death (days after inoculation).