Opisthorchis viverrini is an ongoing public health problem in Northeast Thailand. Despite continuous efforts for decades by healthcare organizations to overcome this problem, infection rates remain high. To enable related personnel to identify and address the various issues effectively, a cross-sectional study was performed to investigate prevalence and risk factors for opisthorchiasis. The target group was 3,916 Thai residents of Northeast Thailand who were 15 or over. Participants were recruited using the 30 clusters sampling technique. The data were gathered through questionnaires, focus group discussions, in-depth interviews, and stool examinations for parasite eggs (using the Modified Kato Katz method). The data were analyzed using descriptive and inference statistics; in order to ascertain the risk factors and test them using the odds ratio and multiple logistic regressions. The prevalence of opisthorchiasis was 22.7% (95%CI: 0.26 to 0.24). The province with the highest prevalence was Nakhorn Phanom (40.9%; female to male ratio =1:1.2). The age group with the highest prevalence was 40-49 year olds. All age groups had a prevalence >20%. Four of seven provinces had a prevalence >20%. The factors related to opisthorchiasis were (a) sex, (b) age (especially > 50), (c) proximity and duration living near a water body, and (d) eating raw and/or fermented fish. In order to reduce the prevalence of opisthorchiasis, the focus in populations living in upper Northeast Thailand should be changing their eating behaviors as appropriate to their tradition and context.

The quantitative formalin ethyl acetate concentration technique (QFEC) was compared to agar plate culture (APC) for the detection of Strongyloides stercoralis larvae. QFEC could substitute for APC only when the parasite load was higher than 50 larvae per g of stool. This study serves as a good reminder to those conducting stool exams about the sensitivity and specificity limitations of both techniques.Agar plate culture (APC) is a highly effective technique for the coprological diagnosis of human strongyloidiasis (1,(5)(6)(7)(8)10). But despite its high sensitivity, there are several disadvantages to APC. It is expensive, it takes a long time before results can be provided, and there is also a risk of infection for the technicians. The quantitative formalin ethyl acetate concentration technique (QFEC) is another effective and more rapid method to detect and quantify intestinal helminths, e.g., Ascaris lumbricoides (3) and Opisthorchis viverrini (4). In the present study, we compared APC results to the different intensities of Strongyloides stercoralis larvae determined by QFEC.Stool samples (n ϭ 1,233) were collected from populations in northeast Thailand and examined by APC (6) and QFEC (3). For APC, 3-g portions of individual fecal samples were placed in the centers of nutrient agar plates during the field survey. The plates were kept in a box and transported at room temperature (30 to 35°C) to the laboratory, where they were incubated for another 5 days at room temperature. The agar plates were examined under a stereomicroscope for the presence of tracks from moving larvae or free-living adults on the 3rd and 5th days. All microscopically positive dishes were further processed by washing the surface of the agar with a 10% formalin solution to collect worms for species identification. The differentiation of S. stercoralis larvae from hookworm larvae was performed under microscopic magnification of ϫ40. For QFEC, 2 g of individual fecal samples was weighed out and then stirred well in a vial containing a merthiolate-iodineformalin solution (2). The preserved stools were processed by QFEC (3). Briefly, the preserved fecal suspension was filtered through two layers of wet gauze into a centrifuge tube. The volume was adjusted to 10 ml with 10% formalin. Two milliliters of ethyl acetate was added, and the tube was closed and shaken for half a second. The stopper was removed, and the tube was centrifuged at 600 ϫ g for 10 min. The plug of debris along with the merthiolate-iodine-formalin solution was discarded by inverting the tube, leaving only the sediment, which was resuspended. The entire suspension was examined under a microscope. The total number of larvae in the sediment was counted and is presented as the number of larvae per gram of stool (lpg). A negative result meant that no larvae were seen in the whole sediment. This study protocol was approved by the Human Research Ethics Committee of Khon Kaen University.Of the 1,233 stool samples, 303 (24.57%) were found to be positive by at least one of the two meth...

Background Control and elimination of the liver fluke (Opisthorchis viverrini) is a primary preventive strategy against cholangiocarcinoma in Southeast Asia. A sensitive parasitological diagnostic method is required to facilitate a surveillance and control program. In this study, we evaluated the performance of Mini Parasep® SF stool concentrator kit (stool kit) compared with Kato-Katz (KK) and the quantitative formalin-ethyl acetate concentration technique (FECT) for detection of O. viverrini and co-endemic parasitic infections. Methods A cross-sectional survey for parasitic infection in residents aged > 15 years in a community in Kalasin province, Northeast Thailand, was conducted in 2018. Fecal samples were collected and screened by KK method, and a subset of samples was further examined by the stool kit and FECT methods. The results were analyzed for prevalence of parasitic infections in addition to the diagnostic performance of the methods for qualitative and quantitative detection of helminthiases. Results The initial survey of parasitic infection determined by the KK method (n = 567) showed the prevalence of O. viverrini was 32.63%, followed by Taenia 2.65%, echinostomes 1.76%, hookworms 1.41%, Trichuris trichiura 0.53% and Strongyloides stercoralis 0.53%. Within a subset of samples tested with multiple diagnostics (n = 150), the detection rates of O. viverrini by the stool kit, FECT and KK methods were 27.3%, 30.7% and 28.7%, respectively. The diagnostic sensitivity for opisthorchiasis was similar for FECT (75.5%), KK(66.0%) and the stool kit (67.3%). For other parasitic infections, FECT and stool kit methods performed better than KK, particularly in detecting minute intestinal flukes (MIF), S. stercoralis and coinfections. When measuring the intensity of O. viverrini infection (fecal egg counts), the stool kit results showed a significant positive correlation with KK and FECT (P < 0.05). Conclusions As the stool kit is simple to use and shows a comparable performance to FECT, it may serve as an alternative method of fecal examination for screening of helminthiasis including opisthorchiasis. Graphical abstract

Background Control and elimination of the liver fluke (Opisthorchis viverrini) is a primary preventive strategy against cholangiocarcinoma in Southeast Asia. A sensitive parasitological diagnostic method is required to facilitate such a surveillance and control program. In this study, we evaluated the performance of Mini Parasep SF stool concentrator kit (stool kit) in comparison with Kato-Katz (KK) and the quantitative formalin-ethyl acetate concentration technique (FECT) for detection of O. viverrini and coexisted parasitic infections. Methods A cross-sectional survey of parasitic infection of residents age <15 years old in a community in Kalasin province, northeast Thailand was conducted in 2018. Fecal samples were collected and screened by KK method and a subset of samples was examined by the stool kit and FECT methods. The results were analyzed for prevalence of parasitic infections and diagnostic performances of methods for qualitative and quantitative detection of helminthiasis. Results The initial survey of parasitic infection determined by the KK method (n=567) showed the prevalence of O. viverrini was 32.63%, followed by Taenia 2.65%, echinostomes 1.76%, hookworms 1.41%, Trichuris trichiura 0.53%, and Strongyloides stercoralis 0.53%. Within a subset of samples tested with multiple diagnostics (n=150), the detection rates of O. viverrini by the stool kit, FECT, and KK methods were 27.3%, 30.7%, and 28.7%, respectively. The diagnostic sensitivity for opisthorchiasis were similar for FECT (75.4%) and KK (70.5%) and was lower for the stool kit (67.2%, p<0.05). For other parasitic infections, FECT and stool kit performed better than KK methods particularly in detecting minute intestinal fluke (MIF), S. stercoralis, and coinfections. The intensity of O. viverrini infection (fecal egg counts) by the stool kit had significant positive correlations with KK as well as FECT (p<0.05). Conclusions As the stool kit is simple to use and showed a comparable performance to FECT, it may serve as an alternative method of fecal examination for screening of helminthiasis including opisthorchiasis.