In this study, the KAPs survey was conducted to explore the level of KAPs of fishermen and boatmen on schistosomiasis in Yueyang County of Hunan Province, P. R. China. Infection status of schistosomiasis in this special group was determined by a sensitive method based on nucleic acid detection and risk factors related to infection were identified through logistic regression models. This study aims to provide information for the design and development of integrated control strategy against schistosomiasis in China.
Our findings showed that the overall awareness of schistosomiasis control knowledge among study participants was considered to be relatively satisfactory, which attributes to the persistent health education conducted for many years. More than 90% respondents knew the cause of getting infection, intermediate host of schistosomes and preventive methods, while majority of the respondents knew this disease, its clinical manifestations and transmission mode. However, less than 70% respondents know the medication against schistosomiasis as well as its impacts on children and female. We also found that majority of the respondents had positive attitudes towards schistosomiasis prevention. More than 95% respondents had the willingness to install feces containers on their boats, using onshore public toilets, and taking medicine against schistosomiasis, which would benefit to the control of schistosomiasis in this population. Nearly 90% participants believed that schistosomiasis was preventable and 71.88% respondents trusted schistosomiasis could be cured.
Despite sufficient knowledge and good attitudes towards schistosomiasis prevention, behavioral practices of fishermen and boatmen were quite unsatisfactory on the contrary. People preferred to receive examination and treatment, rather than to prevent. Only 6.66% respondents had installed latrine on their boats, and only 32.61% respondents defecated in the onshore public toilets. There are many reasons given by interviewed fishermen and boatmen. On the one hand, for example, fishing boats are too small to install fecal containers and stools are easy to overflow out of containers because of the instability on board. On the other hand, feces-induced smell makes containers intolerable on board. In addition, only 4.99% respondents protected themselves when contacting freshwater. These respondents complained it is troublesome and inconvenient to wear protections when fishing or working on the water. Adequate knowledge and positive attitudes didn’t convert to behavior changes effectively, mainly due to the strong economic drives of their works, which was corresponding to former studies [21, 29]. The gaps observed between knowledge, attitude and practices indicated that effective methods and enormous efforts should be made to better address the problem of transmission caused by behavior approaches. First of all, appropriate health promotion activities should be provided to this high-risk population. Secondly, existing intervention approaches should be improved or modified to be more accessible and attractive to fishermen and boatmen. Finally, integrated approaches to eliminate the transmission risk of schistosomiasis in freshwater body should be further explored and strengthened [13]. In addition, the prohibition of fishing activities is going to be implemented along the Yangtze River, which can be literally helpful for current situation. Meanwhile, effective monitoring system needs to be established and run efficiently to guarantee this policy.
In P. R. China, a two-step detection pattern with serological screening first followed by stool examination only for serological positives is applied for field diagnosis of schistosmiasis in China [15]. This pattern presented great advantages in the early age because of its enormous capacity of large-scale screening and examination. However, with the persistent implementation of integrated control strategy for schistosomiasis, the prevalence and intensity of schistosomiasis in China have reached a very low level in history [19, 30]. The infected fishermen and boatmen can be easily misdiagnosed by traditional methods such as Kato-Katz method or miracidia hatching technique, and therefore not targeted for chemotherapy, which brings great potential risks to the elimination of schistosomiasis in China [31, 32]. As a classic nucleic acid amplification technique, PCR method has a varied of advantages over stool examination, such as higher sensitivity and specificity, low cost of reagents and universal equipment in labs, which was considered to hold great potentials of application for schistosomiasis detection in the future [33]. It was reported that only 2.16 eggs per gram feces were needed to detect schistosomiasis by PCR method [33].
This article found a high burden of schistosomiasis in fishermen and boatmen in Yueyang County by PCR method (83/691, 13.81%), which is higher than the average prevalence obtained from national surveillance system[15, 21, 34]. Following explanations as well as considerations are therefore initiated for discussion. Firstly, the study population generally spend most of their lives on board, they therefore contact with S. japonicum-infested water frequently, which is thought to be the main reason for their vulnerability to infection and re-infection of schistosome [32, 35]. Secondly, interventions against schistosomiasis were not accessible to fishermen and boatmen due to their high mobility [24, 36]. Among the 601 respondents in our research, 25 (4.16%) of 601 never received treatment and 220 (36.61%) only received treatment two years ago before our study. Thirdly, our study used nucleic acid-based detection method rather than traditional methods. The PCR technique used in this article performed excellent sensitivity as it could detect 10 pg/µl schistosome genome DNA based on internal assessment, and great specificity reflected by DNA sequencing of PCR products. PCR technique, therefore, can benefit the diagnosis and treatment on individuals with low-level infections and thus promote the elimination of schistosomiasis in P. R. China.
The results from logistic regression showed that four variables including age, years of doing current job, times received treatment in history and whether received treatment in recent two years were significantly associated with PCR results which were used to measure the infection of S. japonicum. Younger fishermen and boatmen are more likely to be infected by schistosomes, which have the similar results in previous research [24]. As main labor forces of their families, young fishermen and boatmen are more likely to be involved in fishing or household chores, which signifies higher frequency and greater level of exposure to S. japonicum-infested water, and therefore have more opportunities to get infected. In addition, there are also studies showing that aged fishermen and boatmen with long-term exposure to water can produce a kind of acquired immunity towards Schistosoma in their bodies, which protects them to a certain degree [5]. We also found that years of doing current jobs were also strongly associated with the infection of S. japonicum. Specifically, the more years doing current job, the higher risk of having positive results determined by PCR. Moreover, our findings showed that the prevalence decreased significantly with treatment times extended among this population. The respondents who have never been treated ever before and those who only been treated once to five times presented positive rates of 32.00% and 17.13%, respectively. Also, prevalence was higher in the subgroup which have not received any treatment in recent two years. These results all indicated that chemotherapy is still an effective way to control schistosomiasis in this population, who keeps being at high risk of infection in lake and marshland regions and serves as the main obstacle of schistosomiasis elimination in P.R. China [25].
One of the limitations in our study is that not all risk factors were considered as its entirety in the analysis, e.g. some of economic and historical elements, which may lost some of information in the study. Secondly, the 152 fishermen and boatmen who were excluded out of the study might have an impact on the study results to some extent. Furthermore, molecular diagnosis technology itself is continuously developing, and PCR technology is gradually improved. Therefore, it is promising for the application of PCR to the epidemiological study in neglected tropical diseases, and to understand the prevalence of disease accurately.