The infection status of
Nowadays
On the other hand, many Korean workers surveyed on freshwater fish, the infection sources of clonorchiasis, collected from various endemic riverside areas to estimate the endemicities of clonorchiasis. The results revealed that more than 49 fish species in 7 families have been reported as the second intermediate hosts of
Wicheon is one of the branch streams of Nakdong-gang, which arises from a mountainous area of Goro-myeon (myeon =township) in Gunwi-gun (gun=county), flows via Gunwigun and Euiseong-gun, and unites with the main stream at Sangju-si (si=city), Gyeongsangbuk-do. The water ecosystem of this stream is more or less healthy but the ecological conditions for fish is not so good [
We collected total 1,162 freshwater fish in 32 species in Wicheon (a stream of Nakdong-gang), which is located in Woobo-myeon, Gunwi-gun (latitude: 38.43268; longitude: 127.4375), Gyeongsangbuk-do, Korea. The numbers and species of fish examined in each year were as follows:
In 2011, total 105 freshwater fish in 13 species (no. of fish examined), i.e.,
In 2014, total 338 freshwater fish in 24 species, i.e.,
In 2016, total 168 freshwater fish in 17 species, i.e.,
All collected fish with ice were transferred to the laboratory of the Department of Parasitology and Tropical Medicine, Gyeongsang National University College of Medicine, Jinju, Korea. After identification of fish species, they were individually ground with a mortar or grinder. Each ground fish meat was mixed with artificial gastric juice, and the mixture was incubated at 36°C for 2 hr. The digested material was filtered with 1×1 mm of mesh, and washed with 0.85% saline until the supernatant became clear. The sediment was carefully examined under a stereomicroscope. The metacercariae of
The gobioninid (Gobioninae) group-1 (323 fish) included
CsMc were detected in 720 (62.0%) out of 1,162 fish in 32 species examined, and their average density was 610 per fish infected. The infection status by fish species and surveyed years is shown in
CsMc were detected in all (100%) of 323 fish examined, and their average density was 1,310 per fish infected. The densities were highest in 2014 (1,958), followed by 2015 (1,582), 2016 (1,211), 2013 (972), 2017 (685), and 2011 (516) (
CsMc were detected in 23 (95.8%) out of 24 fish examined, and their average density was 127 per fish infected. The infection status by fish species, i.e.,
CsMc were detected in 228 (77.0%) out of 296 fish examined, and their average density was 50 per fish infected. The densities were highest in 2015 (93), followed by 2016 (70), 2014 (43), 2011 (20), 2013 (5), and 2017 (5) (
CsMc were detected in 147 (36.5%) out of 403 fish examined, and their average density was 15 per fish infected. The densities were highest in 2015 (25), followed by 2017 (16), 2013 (15), 2014 (11), 2016 (10), and 2011 (7) (
The susceptibility indices of CsMc were 412 in the overall positive fish group; 1,310 in the gobioninid group-1, 122 in the gobioninid group-2, 38.5 in the acheilognathinid, and 5.5 in the rasborinid fish group (
By the present study, it was reconfirmed that CsMc are highly prevalent in fish from Wicheon, Gyeongsangbuk-do, Korea. Moreover, the infection status showed a certain tendency according to the subfamily groups of fish hosts, i.e., Gobioninae, Acheilognathinae, and Rasborinae, among the Cyprinidae. The prevalences were 100%, 79.7%, and 35.5%, and metacercarial densities were 1,310, 50, and 15 per fish infected in 3 fish groups, respectively. These findings also suggested that the endemicity of CsMc is closely related to the fish group, and this host-parasite relationship may originate from a long-lasting evolutional process.
The fish sampling is one of the important factors in metacercarial surveys for the epidemiology of fishborne zoonotic trematode infections. Total 1,162 fish in 32 species were collected through 6 years (2011 and 2013–2017) in the same site of Woobo-myeon in Gunwi-gun. Among them, the pale chub (259
Total 49 fish species (in 34 genera 7 families) have been reported as the second intermediate hosts of
The large mouth bass,
Fish species, i.e., Mandarin fish (
The striped shinner,
Conclusively, it has been confirmed that the endemicity of CsMc is much higher in fish from Wicheon, and a strong tendency was shown in the prevalence and intensity of CsMc according to the subfamily groups of fish, i.e., Gobioninae, Acheilognathinae, and Rasborinae, in the family Cyprinidae fish hosts. Among the highly susceptible gobioninid fish,
This study was supported by an anti-communicable diseases control program, 2014-E54002-00 (Investigation of fish-borne parasites and acquisition of their biological resources in the southern regions of Korea) and 2015-E54001-00 (Investigation of fish-borne parasites and acquisition of their biological resources in the eastern regions of Korea) of National Institute of Health (NIH), Korea Centers for Disease Control and Prevention (KCDCP), Korea. We thank Jung-A Kim and Hee-Joo Kim (Department of Parasitology and Tropical Medicine, Gyeongsang National University College of Medicine, Jinju, Korea), for their help in the examination of fish.
The authors have no conflicts of interest concerning the work reported in this paper.
Infection status of
Year and fish species | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
| |||||
Total | Range | Average | |||
2011 | |||||
|
5 | 5 (100) | 5,216 | 340–2,420 | 1,043 |
|
10 | 10 (100) | 818 | 13–295 | 82 |
|
8 | 8 (100) | 4,960 | 9–1,035 | 620 |
|
2 | 2 (100) | 1,901 | 2–12 | 951 |
|
3 | 3 (100) | 16 | - | 5 |
|
5 | 1 (20.0) | 1 | 2 | 1 |
|
3 | 3 (100) | 91 | 87 | 30 |
|
1 | 1 (100) | 9 | - | 9 |
|
49 | 18 (59.3) | 129 | 1–32 | 7 |
Subtotal | 86 | 51 (59.3) | 13,141 | 1–2,420 | 258 |
| |||||
2013 | |||||
|
20 | 20 (100) | 22,790 | 27–11,290 | 1,140 |
|
9 | 9 (100) | 8,687 | 33–2,720 | 965 |
|
6 | 6 (100) | 2,545 | 26–1,245 | 424 |
|
2 | 2 (100) | 95 | 44–51 | 48 |
|
10 | 10 (100) | 58 | 1–14 | 6 |
|
16 | 6 (37.5) | 23 | 1–10 | 4 |
|
20 | 8 (40.0) | 129 | 1–70 | 16 |
|
15 | 1 (6.7) | 2 | - | 2 |
Subtotal | 98 | 62 (63.3) | 34,329 | 1–11,290 | 554 |
| |||||
2014 | |||||
|
47 | 47 (100) | 116,805 | 6–31,250 | 2,485 |
|
14 | 14 (100) | 25,291 | 140–8,460 | 1,807 |
|
13 | 13 (100) | 20,285 | 132–6,130 | 1,560 |
|
11 | 11 (100) | 8,936 | 13–2,730 | 812 |
|
4 | 4 (100) | 2,911 | 483–1,180 | 728 |
|
1 | 1 (100) | 365 | - | 365 |
|
29 | 29 (100) | 1,099 | 1–184 | 38 |
|
1 | 1 (100) | 12 | - | 12 |
|
25 | 22 (88.0) | 560 | 1–136 | 26 |
|
11 | 9 (81.8) | 782 | 1–290 | 87 |
|
10 | 2 (20.0) | 3 | 1–2 | 2 |
|
2 | 1 (50.0) | 283 | - | 283 |
|
60 | 40 (66.7) | 447 | 1–66 | 11 |
|
50 | 1 (2.0) | 1 | - | 1 |
|
13 | 1 (7.7) | 1 | - | 1 |
|
8 | 1 (12.5) | 1 | - | 1 |
|
7 | 1 (14.3) | 3 | - | 3 |
|
6 | 2 (33.3) | 2 | - | 1 |
Subtotal | 319 | 206 (64.6) | 178,007 | 1–31,250 | 864 |
| |||||
2016 | |||||
|
30 | 30 (100) | 36,686 | 28–9,870 | 1,223 |
|
4 | 4 (100) | 3,603 | 210–1,480 | 901 |
|
2 | 2 (100) | 3,323 | 653–2,670 | 1,662 |
|
2 | 2 (100) | 540 | 36–504 | 270 |
|
1 | 1 (100) | 40 | - | 40 |
|
1 | 1 (100) | 13 | - | 13 |
|
35 | 34 (97.1) | 871 | 2–287 | 26 |
|
15 | 15 (100) | 3,006 | 64–329 | 200 |
|
15 | 8 (53.3) | 25 | 1–9 | 3 |
|
3 | 3 (100) | 327 | 4–255 | 109 |
|
30 | 19 (63.3) | 192 | 1–30 | 10 |
|
1 | 1 (100) | 6 | - | 6 |
Subtotal | 139 | 120 (86.3) | 48,632 | 1–9,870 | 405 |
| |||||
2017 | |||||
|
26 | 26 (100) | 26,736 | 22–8,950 | 1,028 |
|
31 | 31 (100) | 13,161 | 4–2,750 | 425 |
|
3 | 3 (100) | 759 | 156–352 | 253 |
|
7 | 7 (100) | 5,260 | 365–2,225 | 751 |
|
27 | 15 (55.6) | 45 | 1–2,030 | 7 |
|
26 | 19 (73.1) | 129 | 1–30 | 5 |
|
5 | 5 (100) | 26 | 2–12 | 1 |
|
2 | 1 (50.0) | 1 | - | 16 |
|
50 | 21 (42.0) | 345 | 1–205 | 1 |
|
2 | 1 (50.0) | 1 | - | 5 |
|
2 | 1 (50.0) | 5 | - | 387 |
Subtotal | 181 | 120 (66.3) | 46,468 | 1–8,950 | |
| |||||
Total | 1,067 | 720 (67.5) | 439,439 | 1–31,250 | 610 |
Infection status of
Year examined | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
2011 | 25 | 25 (100) | 12,895 | 9–2,420 | 516 |
2013 | 35 | 35 (100) | 34,022 | 26–11,290 | 972 |
2014 | 89 | 89 (100) | 174,228 | 6–31,250 | 1,958 |
2015 | 71 | 71 (100) | 112,342 | 24–7,750 | 1,582 |
2016 | 36 | 36 (100) | 43,612 | 28–9,870 | 1,211 |
2017 | 67 | 67 (100) | 45,916 | 4–8,950 | 685 |
Total | 323 | 323 (100) | 423,015 | 4–31,250 | 1,310 |
Infection status of
Species of fish | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
169 | 169 (100) | 261,986 | 6–31,250 | 1,550 | |
74 | 74 (100) | 64,037 | 4–8,460 | 865 | |
43 | 43 (100) | 71,510 | 9–7,680 | 1,663 | |
25 | 25 (100) | 15,773 | 13–2,730 | 631 | |
12 | 12 (100) | 9,709 | 365–2,225 | 809 | |
Total | 323 | 323 (100) | 423,015 | 4–31,250 | 1,310 |
Infection status of
Species of fish | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
13 | 12 (92.3) | 2,101 | 1–1,325 | 175 | |
6 | 6 (100) | 250 | 10–80 | 42 | |
1 | 1 (100) | 13 | - | 13 | |
3 | 3 (100) | 191 | 12–139 | 64 | |
1 | 1 (100) | 365 | - | 365 | |
Total | 24 | 23 (95.8) | 2,920 | 1–1,325 | 127 |
Infection status of
Year examined | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
2011 | 9 | 5 (55.6) | 101 | 1–87 | 20 |
2013 | 26 | 16 (61.5) | 81 | 1–14 | 5 |
2014 | 77 | 63 (81.8) | 2,727 | 1–290 | 43 |
2015 | 54 | 42 (77.8) | 3,897 | 1–678 | 93 |
2016 | 68 | 60 (88.2) | 4,229 | 1–329 | 70 |
2017 | 60 | 40 (66.7) | 201 | 1–30 | 5 |
Total | 296 | 228 (77.0) | 11,372 | 1–678 | 50 |
Infection status of
Species of fish | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
130 | 122 (93.9) | 4,620 | 1–678 | 38 | |
99 | 55 (55.6) | 691 | 1–136 | 13 | |
35 | 32 (91.4) | 4,870 | 1–295 | 152 | |
15 | 3 (20.0) | 4 | 1–2 | 1.3 | |
4 | 4 (100) | 170 | 2–87 | 43 | |
6 | 5 (83.3) | 855 | 4–283 | 171 | |
7 | 7 (100) | 162 | 2–82 | 23 | |
Total | 296 | 228 (77.0) | 11,372 | 1–678 | 50 |
Infection status of
Year examined | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
2011 | 64 | 18 (28.1) | 129 | 1–32 | 7 |
2013 | 35 | 9 (25.7) | 131 | 1–70 | 15 |
2014 | 110 | 41 (37.3) | 448 | 1–66 | 11 |
2015 | 102 | 39 (38.2) | 974 | 1–420 | 25 |
2016 | 44 | 19 (43.2) | 192 | 1–30 | 10 |
2017 | 62 | 21 (33.9) | 345 | 1–205 | 16 |
Total | 403 | 147 (36.5) | 2,219 | 1–420 | 15 |
Infection status of
Species of fish | No. of fish examined | No. (%) of fish infected | No. of metacercariae detected | ||
---|---|---|---|---|---|
Total | Range | Average | |||
259 | 139 (53.7) | 2,207 | 1–420 | 16 | |
136 | 6 (4.4) | 10 | 1–4 | 2 | |
8 | 2 (25.0) | 2 | - | 1 | |
Total | 403 | 147 (36.5) | 2,219 | 1–420 | 15 |
Susceptibility index of
Group | Susceptibility index | ||||||
---|---|---|---|---|---|---|---|
2011 | 2013 | 2014 | 2015 | 2016 | 2017 | Total | |
Overall positive fish group | 153 | 351 | 558 | 487 | 350 | 257 | 412 |
Gobioninid group-1 | 516 | 972 | 1,958 | 1,582 | 1,211 | 685 | 1,310 |
Acheilognathinid group | 11.2 | 3.1 | 35.2 | 72.4 | 61.7 | 3.3 | 38.5 |
Rasborinid group | 2 | 3.9 | 4.1 | 9.6 | 4.3 | 5.4 | 5.5 |
Prevalence/100× mean metacercarial density per fish infected.