Table 1. Determination of MLD50 of the KFD seed virus by in-vivo titration in mice.
Each dilution of the KFD seed virus was injected intra-cerebrally to five mice of 3–4 weeks old. Plain medium was injected intra-cerebrally to a group of five mice that served as control group and another five mice were injected with undiluted seed virus that served as positive control. Mice were observed for 14 days at every 12 hour intervals for disease symptoms. At the end of 14 days, virus dilutions of 10⁻2, 10⁻3, 10⁻4, 10⁻5, 10⁻6 caused disease symptoms in 100% of mice, whereas virus dilution of 10⁻7 caused disease in 20% of mice and virus dilution of 10⁻8 did not cause symptoms of the disease in any mice. Thus, the one MLD50 of the KFD seed virus (Reed and Muench method) was 10−6.375/0.03 ml.
| Determination of MLD50 of KFD virus | |||||||
|---|---|---|---|---|---|---|---|
| Virus Dilution | Mortality ratio | No. Infected | No. uninfected | Cumulative | Infection Ratio I ___ (I) + (UI) |
Percent Mortality | |
| Infected (I) | Uninfected (UI) | ||||||
| 10¯ 2 | 5/5 | 5 | 0 | 26 | 0 | 26/26 | 100% |
| 10¯ 3 | 5/5 | 5 | 0 | 21 | 0 | 21/21 | 100% |
| 10¯ 4 | 5/5 | 5 | 0 | 16 | 0 | 16/16 | 100% |
| 10¯ 5 | 5/5 | 5 | 0 | 11 | 0 | 11/11 | 100% |
| 10¯ 6 | 5/5 | 5 | 0 | 6 | 0 | 6/6 | 100% |
| 10¯ 7 | 1/5 | 1 | 4 | 1 | 4 | 1/5 | 20% |
| 10¯ 8 | 0/5 | 0 | 5 | 0 | 9 | 0/9 | 0% |