Figure 1Collection sites for wild rodents in scrub typhus endemic regions of South Korea: Yesan in Chungcheongnam-do (CN), Jeonju in Jeollabuk-do (JB), Gurye in Jeollanam-do (JN), and Hapcheon in Gyeongsangnam-do (GN).
Figure 2Annual fluctuation in the population of scrub typhus vectors and O. tsutsugamushi infections in these vectors. (A) Scrub typhus incidence in the collection regions in 2006–2007, (B) trapping rate of rodents, (C) O. tsutsugamushi infection rate in rodents, (D) chigger index, and (E) minimum O. tsutsugamushi positivity rate of chigger mites.
Figure 3Annual fluctuations in the populations of the 8 dominant chigger mite species. (A) L. pallidum, (B) L. orientale, (C) L. scutellare, (D) L. palpale, (E) L. zetum, (F) N. tamiyai, (G) E. koreaensis, (H) N. gardellai.
Table 1Coordinates of the rodent collection sites.
Area |
Detailed location |
N |
E |
Yesan |
Nojeon-ri, Gwangsi-myeon, Yesan-gun, Chungcheongnam-do |
36° 32′ 2.25″ |
125° 45′ 40.7″ |
Jeonju |
Samcheon-dong, Jeonju-si, Jeollabuk-do |
35° 48′ 17.46″ |
127° 08′ 15.81 |
Gurye |
Samsan-ri, Ganjeon-myeon, Gurye-gun, Jeollanam-do |
35° 9′ 28.79″ |
127° 32′ 49.40″ |
Hapcheon |
Jung-ri, Chogye-myeon, Hapcheon-gun, Gyeongsangnam-do |
35° 33′ 40.75″ |
128° 15′ 15.37″ |
Table 2Summary of collection data and O. tsutsugamushi infections in wild rodents and chigger mites.
|
No. of scrub typhus patients |
No. of installed traps |
No. of collected rodents |
Rate of rodent trapping (%) |
No. of rodents infested by chigger mites |
Proportion of rodents infested by chigger mites (%) |
No. of collected chigger mites |
Chigger Index |
No. of Ot positive rodents |
Proportion of Ot positive rodents (%) |
No. of Ot positive chigger mite pools |
No. of tested chigger mites |
Minimum infection rate (%) of chigger mites |
2006 |
|
|
|
|
|
|
|
|
|
|
|
|
|
Jan |
- |
220 |
25 |
11.4 |
12 |
48.0 |
218 |
8.7 |
1 |
4.0 |
- |
50 |
- |
Feb |
- |
270 |
36 |
13.3 |
26 |
72.2 |
1,275 |
35.4 |
- |
- |
3 |
582 |
0.5 |
Mar |
1 |
300 |
38 |
12.7 |
33 |
86.8 |
2,148 |
56.5 |
5 |
13.2 |
8 |
1,011 |
0.8 |
Apr |
- |
265 |
39 |
14.7 |
27 |
69.2 |
2,929 |
75.1 |
5 |
12.8 |
18 |
1,484 |
1.2 |
May |
- |
315 |
42 |
13.3 |
26 |
61.9 |
691 |
16.5 |
1 |
2.4 |
1 |
278 |
0.4 |
Jun |
- |
450 |
67 |
14.9 |
11 |
16.4 |
34 |
0.5 |
1 |
1.5 |
- |
- |
- |
Jul |
- |
441 |
57 |
12.9 |
1 |
1.8 |
1 |
0.0 |
- |
- |
- |
- |
- |
Aug |
- |
430 |
53 |
12.3 |
10 |
18.9 |
81 |
1.5 |
- |
- |
- |
18 |
- |
Sep |
1 |
245 |
23 |
9.4 |
6 |
26.1 |
118 |
5.1 |
- |
- |
- |
29 |
- |
Oct |
77 |
490 |
44 |
9.0 |
25 |
56.8 |
1,713 |
38.9 |
1 |
2.3 |
8 |
813 |
1.0 |
Nov |
141 |
485 |
38 |
7.8 |
27 |
71.1 |
1,773 |
46.7 |
3 |
7.9 |
7 |
832 |
0.8 |
Dec |
11 |
395 |
44 |
11.1 |
41 |
93.2 |
1,741 |
39.6 |
4 |
9.1 |
5 |
745 |
0.7 |
Subtotal |
231 |
4,306 |
506 |
11.8 |
245 |
48.4 |
12,722 |
25.1 |
21 |
4.2 |
50 |
5,842 |
0.9 |
2007 |
|
|
|
|
|
|
|
|
|
|
|
|
|
Jan |
- |
345 |
38 |
11.0 |
28 |
73.7 |
499 |
13.1 |
3 |
7.9 |
- |
166 |
- |
Feb |
- |
360 |
40 |
11.1 |
28 |
70.0 |
2,139 |
53.5 |
4 |
10.0 |
5 |
1,029 |
0.5 |
Mar |
- |
465 |
52 |
11.2 |
43 |
82.7 |
2,838 |
54.6 |
2 |
3.8 |
6 |
1,373 |
0.4 |
Apr |
- |
435 |
46 |
10.6 |
26 |
56.5 |
1,810 |
39.3 |
- |
- |
4 |
848 |
0.5 |
May |
- |
510 |
45 |
8.8 |
18 |
40.0 |
460 |
10.2 |
2 |
4.4 |
2 |
169 |
1.2 |
Jun |
1 |
485 |
47 |
9.7 |
4 |
8.5 |
22 |
0.5 |
1 |
2.1 |
- |
9 |
- |
Jul |
1 |
505 |
48 |
9.5 |
1 |
2.1 |
1 |
0.0 |
- |
- |
- |
- |
- |
Aug |
- |
315 |
30 |
9.5 |
9 |
30.0 |
28 |
0.9 |
- |
- |
- |
- |
- |
Sep |
49 |
335 |
26 |
7.8 |
10 |
38.5 |
150 |
5.8 |
1 |
3.8 |
1 |
47 |
2.1 |
Oct |
136 |
430 |
40 |
9.3 |
38 |
95.0 |
4,517 |
112.9 |
3 |
7.5 |
3 |
2,220 |
0.1 |
Nov |
3 |
435 |
44 |
10.1 |
38 |
86.4 |
5,798 |
131.8 |
- |
- |
25 |
2,779 |
0.9 |
Dec |
190 |
560 |
66 |
11.8 |
54 |
81.8 |
1,577 |
23.9 |
- |
- |
- |
622 |
- |
Subtotal |
421 |
5,180 |
522 |
10.1 |
297 |
56.9 |
19,839 |
38.0 |
16 |
3.1 |
46 |
9,262 |
0.5 |
Total |
|
9,486 |
1,028 |
10.8 |
542 |
52.7 |
32,561 |
31.7 |
37 |
3.6 |
96 |
15,104 |
0.6 |
Table 3Species of chigger mites collected from wild rodents.
|
C. ika
|
E. kor
|
L. ful
|
L. gem
|
L. ori
|
L. pall
|
L. palp
|
L. scu
|
L. sub
|
L. zet
|
N. gar
|
N. jap
|
N. kwa
|
N. tam
|
W. fra
|
L. spp
|
Total |
2006 |
Jan |
- |
1 |
- |
- |
102 |
- |
45 |
- |
1 |
19 |
- |
- |
- |
- |
- |
- |
168 |
Feb |
- |
2 |
- |
- |
168 |
353 |
85 |
1 |
2 |
82 |
- |
- |
- |
- |
- |
- |
693 |
Mar |
1 |
8 |
- |
1 |
458 |
579 |
48 |
5 |
2 |
35 |
- |
- |
- |
- |
- |
- |
1,137 |
Apr |
- |
2 |
- |
- |
453 |
949 |
9 |
1 |
2 |
29 |
- |
- |
- |
- |
- |
- |
1,445 |
May |
1 |
3 |
- |
- |
84 |
303 |
2 |
- |
5 |
5 |
- |
- |
- |
- |
10 |
- |
413 |
Jun |
- |
- |
- |
- |
8 |
22 |
- |
- |
2 |
2 |
- |
- |
- |
- |
- |
- |
34 |
Jul |
- |
- |
- |
- |
1 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
1 |
Aug |
- |
- |
- |
- |
29 |
9 |
- |
- |
- |
- |
19 |
- |
- |
- |
- |
6 |
63 |
Sep |
- |
- |
- |
- |
7 |
48 |
- |
16 |
- |
- |
9 |
- |
- |
- |
- |
9 |
89 |
Oct |
1 |
71 |
- |
- |
61 |
253 |
9 |
504 |
- |
- |
- |
- |
1 |
- |
- |
- |
900 |
Nov |
- |
21 |
- |
- |
128 |
264 |
147 |
361 |
- |
6 |
- |
1 |
1 |
12 |
- |
- |
941 |
Dec |
1 |
23 |
- |
- |
293 |
215 |
274 |
107 |
4 |
58 |
- |
- |
- |
21 |
- |
- |
996 |
Subtotal |
4 |
131 |
- |
1 |
1,792 |
2,995 |
619 |
995 |
18 |
236 |
28 |
1 |
2 |
33 |
10 |
15 |
6,880 |
2007 |
Jan |
- |
6 |
- |
- |
76 |
74 |
137 |
3 |
- |
28 |
- |
- |
- |
9 |
- |
- |
333 |
Feb |
- |
5 |
- |
- |
219 |
638 |
116 |
16 |
7 |
104 |
- |
- |
- |
5 |
- |
- |
1,110 |
Mar |
1 |
5 |
- |
- |
361 |
934 |
87 |
5 |
4 |
60 |
- |
- |
- |
8 |
- |
- |
1,465 |
Apr |
- |
3 |
- |
- |
332 |
582 |
16 |
1 |
5 |
23 |
- |
- |
- |
- |
- |
- |
962 |
May |
1 |
3 |
- |
- |
69 |
208 |
1 |
- |
- |
9 |
- |
- |
- |
- |
- |
- |
291 |
Jun |
- |
- |
- |
- |
3 |
10 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
13 |
Jul |
- |
- |
- |
- |
1 |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
- |
1 |
Aug |
3 |
- |
7 |
- |
10 |
2 |
- |
- |
1 |
- |
5 |
- |
- |
- |
- |
- |
28 |
Sep |
- |
11 |
1 |
- |
33 |
43 |
- |
2 |
1 |
- |
12 |
- |
- |
- |
- |
- |
103 |
Oct |
2 |
88 |
8 |
- |
124 |
817 |
20 |
1,151 |
1 |
11 |
70 |
1 |
- |
2 |
2 |
- |
2,297 |
Nov |
- |
41 |
- |
- |
180 |
918 |
613 |
892 |
2 |
116 |
2 |
2 |
- |
253 |
- |
- |
3,019 |
Dec |
- |
10 |
- |
- |
101 |
372 |
243 |
91 |
2 |
50 |
- |
- |
- |
86 |
- |
- |
955 |
Subtotal |
7 |
172 |
16 |
- |
1,509 |
4,598 |
1,233 |
2,161 |
23 |
401 |
89 |
3 |
- |
363 |
2 |
- |
10,577 |
Total |
11 |
303 |
16 |
1 |
3,301 |
7,593 |
1,852 |
3,156 |
41 |
637 |
117 |
4 |
2 |
396 |
12 |
15 |
17,457 |
% |
0.1 |
1.7 |
0.1 |
0.0 |
18.9 |
43.5 |
10.6 |
18.1 |
0.2 |
3.6 |
0.7 |
0.0 |
0.0 |
2.3 |
0.1 |
0.1 |
100.0 |