Table 1.
Host-to-tick transmission of B. afzelii and the spirochete load of the infected I. ricinus nymphs are shown for the ten combinations of strain (A3 or A10) and the age of infection (2, 34, 66, 94 and 128 days). The probability of transmission shows the number of infected nymphs divided by the total number of nymphs analysed, and the corresponding percentage of infected nymphs. The spirochete load presents the mean spirochete load and the 95% confidence interval (CI) for the subset of infected nymphs
| Strain | Age of infection (days) | Transmission | Spirochete load | |
|---|---|---|---|---|
| Infected nymphs/total nymphs (%) | Meana | 95% CI | ||
| A3 | 2 | 14/105 (13.3) | 2,591 | 1,711–3,924 |
| A3 | 34 | 75/100 (75.0) | 10,496 | 8,163–13,496 |
| A3 | 66 | 54/95 (56.8) | 9,064 | 7,301–11,251 |
| A3 | 94 | 57/90 (63.3) | 9,853 | 7,822–12,411 |
| A3 | 128 | 62/90 (68.9) | 8,100 | 6,811–9,633 |
| A10 | 2 | 98/190 (51.6) | 6,436 | 5,548–7,465 |
| A10 | 34 | 118/130 (90.8) | 19,250 | 17,214–21,528 |
| A10 | 66 | 73/118 (61.9) | 18,488 | 15,971–21,402 |
| A10 | 94 | 88/128 (68.9) | 32,087 | 28,593–36,009 |
| A10 | 128 | 79/128 (61.7) | 18,806 | 17,058–20,735 |
| Total | 718/1,174 (61.2) | |||
aFor each of the ten combinations of strain and age of infection, the geometric mean spirochete load in the nymphal tick was calculated for each mouse (uninfected nymphs were excluded). For strains A3 and A10, the geometric mean nymphal spirochete load and the 95% confidence interval are based on 10 and 13 mice, respectively