S. mekongi remains a public health concern in the communities on islands in the Khong district, Champasack province, in the southern part of Lao PDR [2]. Other helminth parasites such as O. viverrini, hookworm and T. trichiura were also highly endemic. We employed an eco-health/one-health intervention package including promotion of latrine construction and its use, annual MDA with praziquantel and albendazole in humans and dogs, and two health education campaigns in six villages on two islands (three villages each) in Kong district to control these helminth infections.
Our trial revealed a successful installation of latrines with a coverage of over 85% in less than one year, attaining almost 100% coverage on less than one and a half years in the intervention island. Access to adequate sanitation is an essential indicator embodied in the sustainable development goals (SDG 6) on clean water and sanitation, which have been endorsed by the government of Lao PDR [28]. In recent years, the Lao Ministry of Health has made substantial efforts to achieve open defecation-free (ODF) status for all households across the country by implementing the community-led total sanitation programme [29]. However, latrine coverage varies considerably by setting, with the lowest coverage observed in the remote areas, coinciding with places wherein most households in the community faced economic disadvantage and were unable to cover the costs of the construction [29, 30]. In this study, we offered minimal subsidies to the households on the study islands, such as toilet bowls, septic tanks, and metal roofs, which considerably encouraged the contribution and participation of endemic communities in latrine construction. This could be a possible solution for a rapid uptake of latrine construction, which might increase latrine coverage to fulfil ODF status and SDG targets.
Still, the dramatic increase in latrine coverage to almost all households did not result in complete open defecation-free practices among study participants. Our follow-up showed that one in every six participants from the intervention island continued open defecation practices. The professional activities such as farming on rice fields might put them in places where no latrines are available. Nonetheless, open defecation decreased by three times when compared to the baseline observations and was significantly lower than on control island (OR = 0.45, P < 0.001). The incomplete reduction of open defecation was similar to our previous study, in which we observed that 19.5% of study participants still practiced open defecation after having a latrine in their households [31].
Our findings suggest that a thorough health education campaign is effective to increase awareness of diseases among inhabitants in the endemic communities. The health education campaigns on the intervention increased knowledge about schistosomiasis more than 23 times (P < 0.001) when compared to the control island. Participants who knew that schistosomiasis was endemic in their community increased by 15.7 times compared to the control island (P < 0.002). Participants who perceived that schistosomiasis can be prevented increased more than three times compared to the control island (P = 0.047). Our findings are aligned with previous studies conducted in different regions, which concluded that health education improved the participants’ KAP towards disease prevention and control, including helminthiases [32, 33].
We found that the eco-health/one-health intervention package employed in the study island in the first stage of the trial significantly reduced the S. mekongi infection in the first assessment and long-term evaluations both on prevalence and intensity of infection. These findings confirm the previous reports suggesting that an integrated intervention could be an ideal approach for driving S. mekongi control programmes to reach elimination goals [31, 34]. In our study, the assessment one year after the completion of the intervention implementation showed a reduction of twofold in S. mekongi infection in the intervention when compared to the control villages (OR = 0.49, P < 0.001). After implementation of the intervention package on the control island, the reduction in prevalence of S. mekongi continued steadily on both islands reaching the lowest prevalence of 1.8% for intervention and 3.1% for control in 2017, respectively.
Our study also showed a significant impact of this integrated package on O. viverrini and hookworm infections, which are helminths infection of public health concern in the study area and Lao PDR. Our one year of assessment revealed that O. viverrini infection decreased by 20.3 times in the intervention island when compared to the control island (P < 0.001). For hookworm, the odds of infection decreased by 17.9 times (P < 0.001) compared to the control island. For longer-term assessment, the reduction in prevalence was not achieved at a level of much less than 20% for O. viverrini and for hookworm, which is the cut-off point WHO recommended in the national strategy for selective case treatment (no MDA is required) in the endemic community [21]. The high prevalence of O. viverrini (i.e., intervention: 82.7% and control: 52.9%) and hookworm (i.e., intervention: 54.1% and control: 448%) possibly created favourable conditions for dynamic transmission, especially when coupled with continued risk practices such as raw fish consumption and agricultural cultivations of inhabitants, which resulted in heavy re-infections among study participants.
The praziquantel treatment in dogs cleared S. mekongi infection in the study villages on intervention island, while O. viverrini infection was also significantly reduced among the dogs in the invention (5.1%) and control (7.3%) villages in one year of the follow-up assessment. However, dogs are not the main animal reservoir for O. viverrini, and other animal reservoirs (cats and pigs) infected with O. viverrini, hookworm and T. trichiura were unaltered, which allowed them to continue shedding the parasite eggs into the environment in endemic settings [35, 36].
The current study has several limitations. It is important to note that our study used the Kato-Katz technique to diagnose helminth infections, which did not allow us to distinguish between O. viverrini and minute intestinal fluke infections since the egg morphology is extremely similar. Therefore, some of the eggs reported as O. viverrini might be eggs of minute intestinal flukes. Because some participants were lost to follow-up in 2015, the follow-up changed from individuals to communities. This led to a rise in the number of people infected with helminths like O. viverrini and hookworm, since these people may not have gotten treatment during the MDA campaigns.