Table 3. Bacterial loads and transmission efficiency for X. cheopis infected using an artificial feeder system containing defibrinated rat blood infected with Y. pestis at concentrations ranging from 2.35×107 to 5.25×108 c.f.u. ml−1*.
| Strain/mouse | No. infected fleas fed on naïve mouse (total no. fed/total no. exposed to mouse) | Median (range) bacterial load per infected flea fed on naïve mouse | Transmission from flea to mouse | Minimum observed transmission efficiency (%) |
| CO96-3188 | 6.30×104 (5.00 to 2.27×106)† | 1.82 (0.11–8.91)‡ | ||
| 1 | 5 (7/10) | 3.20×104 (1.50×102 to 2.06×105) | No | 0.0 |
| 2 | 9 (10/10) | 8.15×104 (6.60×102 to 4.15×105) | Yes | 11.1 |
| 3 | 10 (10/10) | 2.58×105 (5.05×103 to 2.27×106) | No | 0.0 |
| 4 | 5 (9/10) | 3.80×104 (1.60×102 to 3.21×105) | No | 0.0 |
| 5 | 9 (10/10) | 3.17×104 (2.00×101 to 4.00×105) | No | 0.0 |
| 6 | 10 (10/10) | 3.60×104 (2.90×103 to 1.03×106) | No | 0.0 |
| 7 | 9 (10/10) | 1.90×104 (5.00 to 1.62×105) | No | 0.0 |
| KIM5+ | 1.83×105 (5.00 to 3.15×106)† | 1.90 (0.11–9.41)‡ | ||
| 1 | 9 (10/10) | 2.06×105 (6.00×101 to 3.15×106) | No | 0.0 |
| 2 | 10 (10/10) | 5.10×105 (3.20×103 to 1.95×106) | Yes | 10.0 |
| 3 | 10 (10/10) | 1.96×105 (5.00 to 1.61×106) | No | 0.0 |
| 4 | 8 (10/10) | 1.31×105 (1.50×101 to 8.20×105) | No | 0.0 |
| 5 | 10 (10/10) | 7.15×104 (3.00×101 to 2.95×105) | No | 0.0 |
| 6 | 8 (9/10) | 2.27×105 (1.00×101 to 1.10×106) | No | 0.0 |
| ymtH188N | 1.23×105 (5.00 to 3.45×106)† | 4.59 (1.26–12.24)‡ | ||
| 1 | 8 (9/10) | 2.45×104 (1.80×102 to 1.21×106) | No | 0.0 |
| 2 | 9 (9/10) | 6.70×102 (5.00 to 1.77×106) | No | 0.0 |
| 3 | 5 (9/10) | 6.25×105 (3.00×105 to 2.80×106) | No | 0.0 |
| 4 | 5 (9/10) | 1.94×105 (1.55×102 to 3.45×106) | Yes | 20.0 |
| 5 | 8 (10/10) | 3.80×105 (2.50×103 to 1.07×106) | No | 0.0 |
| 6 | 6 (10/10) | 1.90×105 (2.00×102 to 3.40×105) | No | 0.0 |
| 7 | 9 (9/10) | 6.35×104 (8.15×102 to 9.00×105) | Yes | 11.1 |
| 8 | 6 (10/10) | 2.60×104 (2.05×102 to 1.66×105) | Yes | 16.7 |
| 9 | 7 (10/10) | 1.58×105 (3.60×102 to 5.15×105) | No | 0.0 |
| 10 | 4 (10/10) | 5.98×104 (2.20×102 to 2.35×105) | No | 0.0 |
*
Range of bacterial concentrations in artificial feeders for each strain: CO96-3188 (2.35×107–3.40×108 c.f.u. ml−1), KIM5+ (1.53×108–2.3×108 c.f.u. ml−1) and ymtH188N (1.19×108–5.25×108 c.f.u. ml−1).
†
Median and range of c.f.u. per flea for each strain.
‡
Estimated transmission efficiency (95 % confidence interval) per strain based on maximum likelihood (PooledInfRate, v. 4.0; Biggerstaff, 2009).