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 qualified 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). A total of 59.90% (360/601) of respondents were sideline fishermen and boatmen, while 38.27% (230/601) were professional boatmen. 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.
Participants’ KAPs toward Schistosomiasis
Awareness of Schistosomiasis Knowledge
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 all the populations were susceptible for infection of schistosomes. The majority (95.67%, 575/601) of fishermen and boatmen mentioned snails as the intermediate host of S. japonicum while 75.04% (451/601) of them knew the final host of S. japonicum. Of those surveyed, 97.00% (583/601) mentioned contacting with S. japonicum-infested water was the way to get infection of schistosomes. In terms of their knowledge of the symptoms and effects of schistosomiasis, 86.69% (521/601) of study respondents mentioned fever and diarrhea to be the main symptoms of schistosomiasis, while 58.40% (351/601) knew that schistosomiasis would have severe impacts 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 interviewed fishermen and boatmen mentioned avoiding contact with S. japonicum-infested water as an effective preventive measure. Only 47.92% (288/601) of study participants mentioned praziquantel as an anti-schistosome drug (Table 2).
Attitude to Schistosomiasis Prevention and Control
Most respondents (95.34%, 573/601) indicated that they were willing to install feces containers on their boats. Of the 28 participants who refused to install feces containers, 57.14% complained that fishing boats were too small to accommodate it. 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 study respondents (98.50%, 592/601) were willing to accept examination for schistosomiasis and if diagnosed as positives, 98.50% (592/601) of the study participants expressed a 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).
Practices of the Study Participants 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 ointment. Being too troublesome was the main reason mentioned by 83.98% (471/561) of those not always protecting themselves when contacting freshwater in Dongting Lake. 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 qualified 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 no statistical difference was detected (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).
Based on univariate logistic regression analysis, 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).