Sociodemographic characteristics
A total of 753 fishermen and boatmen were enrolled in this cross-sectional study. However, 122 people provided none or insufficient amounts of stool to prepare for PCR and 30 individuals had no or incomplete questionnaire data. Therefore, 601 individuals who completed the questionnaire and provided adequate stool samples were included in the final analysis. The sociodemographic characteristics of the respondents are presented in Table 1. The number of males was 345 (57.40%) and females was 256 (42.60%). The mean age of respondents was 50.04 years-old (standard deviation, SD = 10.97). Of the 601 respondents, 59.90% (360/601) were non-professional fishermen and boatmen, while 38.27% (230/601) and 1.83% (11/601) were professional boatmen and fishermen respectively. The majority (63.39%, 381/601) had been in their current job for 10–29 years, followed by those who have had their job for more than 30 years (128/601, 21.30%). Over 95% of respondents (576/601) had received treatment against schistosomiasis at least once. The majority of participants (72.05%, 433/601) were from families having an annual household income less than 10,000 Chinese Yuan (about 1511 USD).
Table 1 Major sociodemographic characteristics of the respondents attending KAPs survey and provided stool samples
Variables
|
Category
|
Frequency
|
Percentage (%)
|
Gender
|
Male
|
345
|
57.40
|
Female
|
256
|
42.60
|
Occupation
|
Professional fisherman
|
11
|
1.83
|
Professional boatman
|
230
|
38.27
|
Non-professional fisherman and boatman
|
360
|
59.90
|
Age group
(years)
|
< 30
|
21
|
3.49
|
30–39
|
54
|
8.99
|
40–49
|
228
|
37.94
|
50–59
|
184
|
30.62
|
≥ 60
|
114
|
18.97
|
Education
|
Below primary school
|
57
|
9.48
|
Primary school
|
167
|
27.79
|
Junior middle school
|
324
|
53.91
|
High school and higher education
|
53
|
8.82
|
Participants’ KAPs towards schistosomiasis
Knowledge about schistosomiasis
Of the 601 respondents, 74.88% (450/601) knew that the susceptible season for infection with S. japonicum is from April to October and 72.05% (433/601) knew that the general population is susceptible to infection with schistosomes. The majority (95.67%, 575/601) of respondents mentioned snails as the intermediate host for S. japonicum while 75.04% (451/601) of them knew the definitive host as humans and livestock. Of those surveyed, 97.00% (583/601) mentioned contact with S. japonicum-infested water as the way to become infected. In terms of participants’ knowledge on symptoms and effects of schistosomiasis, 86.69% (521/601) of respondents mentioned fever and diarrhea as the main symptoms of schistosomiasis, while 58.40% (351/601) said that schistosomiasis could have a severe impact on females, and 62.73% (377/601) indicated that schistosomiasis could limit children’s physical growth. With respect to preventive activities and treatment for schistosomiasis, 96.17% (578/601) of respondents mentioned avoiding contact with S. japonicum-infested water as an effective preventive measure. Only 47.92% (288/601) of respondents mentioned praziquantel as an anti-schistosome drug (Table 2).
Table 2 Knowledge of schistosomiasis among the respondents
Knowledge regarding schistosomiasis
|
Response
|
Frequency
|
Percentage (%)
|
Transmission season
(CA: April to October)
|
Correct
|
450
|
74.88
|
Incorrect
|
151
|
25.12
|
Susceptible population
(CA: Everyone)
|
Correct
|
433
|
72.05
|
Incorrect
|
168
|
27.95
|
Definitive hosts
(CA: humans and livestock)
|
Correct
|
451
|
75.04
|
Incorrect
|
150
|
24.96
|
Intermediate hosts
(CA: Oncomelania)
|
Correct
|
575
|
95.67
|
Incorrect
|
26
|
4.33
|
Cause of infection
|
Correct
|
583
|
97.00
|
(CA: contact infected water)
|
Incorrect
|
18
|
3.00
|
Main symptoms
(CA: fever, diarrhea)
|
Correct
|
521
|
86.69
|
Incorrect
|
80
|
13.31
|
Effects on children
(CA: Stagnant physical growth, etc.)
|
Correct
|
377
|
62.73
|
Incorrect
|
224
|
37.27
|
Effects on women
(CA: Infertility, etc.)
|
Correct
|
351
|
58.40
|
Incorrect
|
250
|
41.60
|
Preventive measures
(CA: Do not have contact with infected water)
|
Correct
|
578
|
96.17
|
Incorrect
|
23
|
3.83
|
Medicine used for treatment
|
Correct
|
288
|
47.92
|
(CA: Praziquantel)
|
Incorrect
|
313
|
52.08
|
Abbreviation: CA, correct answer
Attitude to schistosomiasis prevention and control
Most respondents (95.34%, 573/601) indicated that they were willing to install toilet facilities on their boats. Of the 28 respondents who refused to install toilet facilities, 57.14% complained that fishing boats were too small to accommodate any toilet facility. With regard to visiting onshore public toilets, 96.17% (578/601) reported that they would like to use onshore public toilets, while 72.7% of respondents who were reluctant to use onshore public toilets gave the reason that it was inconvenient to go ashore to find toilets over such a long distance when they were working in the middle of the lake. The majority of respondents (98.50%, 592/601) were willing to accept examination for schistosomiasis and 98.50% (592/601) of the respondents expressed willingness to take medicine regularly following doctors’ prescriptions if diagnosed as positive. Of those surveyed, 89.85% (540/601) believed this disease could be prevented, while 71.88% (432/601) understood schistosomiasis could be cured (Table 3).
Table 3 Attitude and practices toward schistosomiasis prevention and control among the respondents
Attitude and practices toward schistosomiasis
|
Category
|
Frequency
|
Percentage (%)
|
Willingness to install toilet facilities
|
Yes
|
573
|
95.34
|
No
|
28
|
4.66
|
Willingness to use onshore public toilets
|
Yes
|
578
|
96.17
|
No
|
23
|
3.83
|
Willingness to accept examination
|
Yes
|
592
|
98.50
|
No
|
9
|
1.50
|
Willingness to take medicine
|
Yes
|
592
|
98.50
|
No
|
9
|
1.50
|
Belief that schistosomiasis could be prevented
|
Yes
|
540
|
89.85
|
No
|
61
|
10.15
|
Belief that schistosomiasis could be cured
|
Yes
|
432
|
71.88
|
No
|
169
|
28.12
|
Install and use toilet facilities
|
Yes
|
40
|
6.66
|
No
|
561
|
93.34
|
Defecate in public toilets onshore
|
Yes
|
196
|
32.61
|
No
|
405
|
67.39
|
Protection when contacted water
|
Yes
|
30
|
4.99
|
No
|
571
|
95.01
|
Practices towards schistosomiasis
Of the 601 respondents, only 6.66% installed and used fecal containers in the correct way. In terms of protective behaviors when contacting S. japonicum-infested water, only 4.99% (30/601) of the respondents reported always wearing rubber shoes, gloves, protective clothing or using ointment on their skin. The main reason given by respondents who did not protect themselves when contacting freshwater in the Dongting Lake was that it was a bother (83.98%, 471/561). Only 32.61% (196/601) of the participants reported always defecating in onshore public toilets (Table 3).
Schistosoma japonicum infection status and related risk factors
Among 601 participants who provided adequate stool samples, 13.81% (83/601) were detected as positive by PCR. The PCR amplification products of all positive samples were sequenced and the results showed that the DNA fragment was 469 bp, which was consistent with the target DNA both in length and sequence (Fig. 2). The positive rate of Schistosoma DNA in males (14.78%) was higher than that of females (12.50%), but not statistically different (χ2 = 0.643, df = 1, P = 0.423). The subgroup of participants who were aged less than 30 years-old, performing their current job for more than 30 years, never been treated for schistosomiasis, or not received treatment during 2015–2017, presented the highest PCR positive rates of 38.10% (8/21), 21.09% (27/128) and 32.00% (8/25), respectively, when conducting strata analysis (Table 4).
Based on univariate logistic regression analysis (Additional file 2: Table S2), nine independent variables were included in the multivariate logistic regression, including age, occupation, economic conditions, years of doing current job, infection history, diagnostic method, disease category, times received treatment, and whether received anti-schistosome treatment from 2015–2017.
The results of multivariate logistic regression analysis indicated that respondents aged 40–49, 50–59 and ≥ 60 years-old had significantly lower odds of being positive than younger groups (< 30, 30–39), as determined by PCR (OR40-49 = 0.163, 95% CI: 0.041–0.644; OR50-59 = 0.058, 95% CI: 0.014–0.239; OR≥60 = 0.012, 95% CI: 0.002–0.065). The fishermen and boatmen who had performed their current job for 10–29 years and over 30 years were more likely to be PCR positive (OR10-29 = 4.162, 95% CI: 1.461–11.856 and OR≥30 = 18.684, 95% CI: 5.430–64.295, respectively) (Table 4). In addition, the respondents who received treatment 6 to 10 times, or more than 10 times showed lower odds of presenting positive PCR results (OR6-9 = 0.156, 95% CI: 0.035–0.689) and OR≥10 = 0.100, 95% CI: 0.021–0.476), compared to those never receiving treatment for schistosomiasis. Respondents who received treatment from 2015 to 2017 were more likely to have negative PCR results (OR= 0.479, 95% CI: 0.246–0.930) (Table 4).
Table 4 Multiple logistic regression analysis of variables associated with S. japonica among the respondents
Risk factors
|
Positive rate (%) determined by PCR (No. positives/No. examined)
|
OR (95% CI)
|
P-value
|
Age group (years)
|
< 30
|
38.10 (8/21)
|
1
|
|
30–39
|
27.78 (15/54)
|
0.318 (0.075–1.354)
|
0.1212
|
40–49
|
15.35 (35/228)
|
0.163 (0.041–0.644)
|
0.0096*
|
50–59
|
10.33 (19/203)
|
0.058 (0.014–0.239)
|
< 0.0001*
|
≥ 60
|
5.26 (6/114)
|
0.012 (0.002–0.065)
|
< 0.0001*
|
Years of doing current job
|
< 10
|
7.61 (7/92)
|
1
|
|
10–29
|
12.86 (49/381)
|
4.162 (1.461–11.856)
|
0.0076*
|
≥ 30
|
21.09 (27/128)
|
18.684 (5.430–64.295)
|
< 0.0001*
|
Treatment times
|
0
|
32.00 (8/25)
|
1
|
|
1–5
|
17.13 (37/216)
|
0.265 (0.064–1.095)
|
0.0666
|
6–9
|
12.26 (26/212)
|
0.156 (0.035–0.689)
|
0.0142*
|
≥10
|
8.11 (12/148)
|
0.100 (0.021–0.476)
|
0.0038*
|
Treatment in 2015–2017
|
No
|
18.18 (40/220)
|
1
|
|
Yes
|
11.29 (43/381)
|
0.479 (0.246–0.930)
|
0.0298*
|
*Significant association (P < 0.05)
Abbreviations: OR, odds ratio; CI, confidence interval