Volume 18, Number 10—October 2012
Rickettsia parkeri and Candidatus Rickettsia andeanae in Gulf Coast Ticks, Mississippi, USA
|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).
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