Socio-Demographic 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 sufficient stool samples were included in the final analysis. The socio-demographic 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, ±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 jobs for 10 to 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 annual household income less than 10 000 Chinese Yuan (about 1511.26 USD).
<Table 1 near here>
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 was from April to October and 72.05% (433/601) knew that the general population was 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 get 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 severe impact on females, and 62.7% (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 near here>
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 regards 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 if diagnosed as positives, 98.50% (592/601) of the respondents expressed willingness to take medicine regularly following doctors' prescriptions. 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 near here>
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% or 471/561). Only 32.61% (196/601) of the participants reported always defecating in onshore public toilets (Table 3).
S. 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 the 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 nucleic acid in males (14.78%) was higher than that of females (12.50%), but not statistically different (χ2=0.643,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), 32.00% (8/25) when conducting strata analysis (Table 4).
<Figure 2 near here>
<Table 4 near here>
Based on univariate logistic regression analysis (see additional file 2), 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 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 to 29 years and over 30 years were more likely to be PCR positives, with an OR10-29 = 4.162 (95%CI: 1.461-11.856), OR≥30= 18.684 (95%CI: 5.430-64.295), respectively (Table 4). In addition, the respondents who received treatment six 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), 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).