Volume 18, Number 10—October 2012
Letter
Rickettsia parkeri and Candidatus Rickettsia andeanae in Gulf Coast Ticks, Mississippi, USA
Table
Location (no. collection sites) | No. ticks | No. (%; 95% CI) SFG rompA | No. (%; 95% CI) R. parkeri only | No. (%; 95% CI) Candidatus R. andeanae only | Expected no. (%) co-infected ticks | No. (%; 95% CI) co-infected ticks |
---|---|---|---|---|---|---|
North (4) | 257 | 49 (19.1; 14.5–24.4)† | 48 (18.7; 14.1–24)‡ | 0§ | 0.19 (0.07) | 1 (0.4; 0–2.1)¶ |
Central (1) | 38 | 4 (10.5; NA) | 1 (2.6; NA) | 2 (5.3; NA) | 0.16 (0.42) | 1 (2.6; NA) |
South (5) | 403 | 75 (18.6; 14.9–22.8)† | 57 (14.1; 10.9–17.9)‡ | 8 (2.0; 0.9–3.9)§ | 2.99 (0.74) | 10 (2.5; 1.2–4.5)¶ |
Total (10) | 698 | 128 (18.3; NA) | 106 (15.2; NA) | 10 (1.4; NA) | 3.65 (0.52) | 12 (1.7; NA) |
*The estimated value of co-infection caused by chance alone (E) was calculated by using the formula E = (a + b)(a + c) / (a + b + c + d) (5), where a = no. ticks infected with both Rickettsia species, b = no. ticks infected only with R. parkeri, c = no. ticks infected only with Candidatus R. andeanae, and d = no. ticks not infected with either Rickettsia species. SFG rompA, spotted fever group rickettsial outer membrane protein A gene. NA, not applicable.
†p = 0.9187.
‡p = 0.1275.
§p = 0.0257.
¶p = 0.0578 (comparison of prevalence from northern and southern sites only).
References
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