Misclassification of Opisthorchis viverrini and Minute Intestinal Fluke Eggs by Routine Laboratory Staff Using Images from the Kato-Katz Method.

BACKGROUND: The Kato-Katz method is a commonly used diagnostic tool for helminth infections, particularly in field studies. This method can yield inaccurate results when samples contain eggs that are similar in appearance, such as Minute Intestinal Fluke (MIF) and Opisthorchis viverrini (OV) eggs. The close resemblance of eggs can be problematic and raises the possibility of false diagnoses. The objectives were to compare the diagnostic performance of the Kato-Katz method for accurately identifying MIF and OV and to provide evidence of possible misclassification.  Methods: Based on questionnaire responses from 15 (young parasitologists and public health staff), the test comprised 50 MIF egg images and 50 OV egg images, for a total of 100 Google Form questionnaires. RESULTS: The morphology of MIF and OV eggs found size and shape similarity and found that the shoulder rims were small, while the OV egg found the knobs had disappeared. The opercular conjunction was apparent, the shoulder rims and miricidium were prominent. The average percentage of correctly classified infections was 61.6 ± 12.1%. The accuracy percentages for both public health staff and young parasitologists in identifying were found to be 59.0 ± 14.8 and 66.8 ± 2.8, respectively. There was no significant difference observed in both groups. CONCLUSION: These findings highlight the need for improving the accuracy of parasite identification. Preserving stool samples before the Kato-Katz method can help mitigate the potential degradation or distortion of parasite eggs. The incorrect classification of both eggs had an impact on treatment plans and the policy of parasite control programs.

Formalin-fixed stool improves the performance of the Kato-Katz method.

Background and Aim: Parasitic infections are a public health problem worldwide, including in Thailand. An epidemiological survey for helminthiasis based on stool examination uses the Kato-Katz method as recommended by the World Health Organization. Limitations of this method include the need for fresh stool, time requirement, and lack of quality control. The aim of this study was to enhance the efficiency of the Kato-Katz technique using formalin and glycerol solutions and to implement specimen preparation in fieldwork. Materials and Methods: For the Kato-Katz method, stool samples were divided into formalin-fixed and unfixed groups at various time points and processes. Fresh echinostome eggs were added to each stool group. Incubation with glycerol increased the clearing process. Each group was observed and photographed using a light microscope. Parasite eggs were imaged and compared using the standard Kato-Katz method. Results: Visualization of echinostome eggs from formalin-fixed stool slides was significantly better than that from unfixed stool slides (p < 0.01). Stool samples fixed for 7 days retained normal echinostome eggs morphology. Incubation with glycerol for 1 h resulted in increased Kato-Katz performance by digesting the stool content and enhancing egg observation. Moreover, the results of the Kato-Katz method using fixed and fixed stool plus glycerol for natural helminth infection showed good quality of Opisthorchis viverrini and Taenia egg visualization and normal morphology with a clear background of slides. Conclusion: Formalin-fixed stool could be more suitable than fresh stool for the Kato-Katz method.

OVCCA Web Application as Supplementary Material to Facilitate Health Literacy Regarding Carcinogenic Human Liver Fluke: A Randomized Controlled Trial in Thailand.

BACKGROUND: Liver fluke, Opisthorchis viverrini, is associated to cholangiocarcinoma which is found frequently in some areas of Southeast Asian countries particularly in Thailand, Lao People Republic Democratic, Cambodia.  This study sought to investigate the effects of an O. viverrini and cholangiocarcinoma (OVCCA) web application to facilitate health literacy regarding O. viverrini in Northeast Thailand. METHODS: A randomized controlled trial study was performed among an intervention group (n=63) and a control group (n=63) during a one-year period from July 2019 to May 2020. The intervention group received the health literacy promotion program of O. viverrini information through the OVCCA web application for 6 weeks. The control group received an activity package from the public health department. The success of the program was evaluated at week 24 after the groups finished the last activity. ANCOVA, t-test and multiple logistic regression were used for data analysis for both groups. RESULTS: The scores for knowledge; ability to access, understand, appraise, and apply information; motivation for protection; and practice of O. viverrini prevention were significantly higher for the intervention group than for the control group. The results indicated that a health literacy promotion program through an OVCCA web application could be advantageous for preventing and controlling O. viverrini infection. CONCLUSION: This intervention may be used as a potential strategy and guideline for self-care and health promotion in other endemic areas.

Current status of helminthiases in Thailand: A cross-sectional, nationwide survey, 2019.

Helminthiases are common neglected tropical diseases in Thailand, thus regular surveillance is necessary for their control. During fiscal year 2019, the Thailand Ministry of Public Health carried out a cross-sectional nationwide survey in people of all age groups from the 12 Regional Health Offices in 76 provinces of Thailand. Multi-stage cluster random sampling design was employed to assess the prevalence of helminth infections and certain behavioural risk factors. A total of 16,187 stool samples and demographic data were obtained from the participants. Stool examination was done and parasite eggs/lavae were identified microscopically by experienced technicians. Positive stool samples for Opisthorchis viverrini, hookworms, or Ascaris lumbricoides were further quantified and expressed in eggs per gram feces (EPG). The results revealed an overall prevalence of helminthic infections of 9.79% with over 14 species identified. The highest prevalence was hookworms (4.47%) followed by O. viverrini (2.2%) with mean infection intensities of 222.7 EPG and 120.9, respectively. The majority of the infections were low intensity (97.4% for hookworms and 99.1% for O. viverrini). Similarly for A. lumbricoides, 93.9% of the positive cases were low infections. Two major helminthiases caused by hookworms and O. viverrini were highlighted in this report. While the liver fluke was highly endemic in Northeast Thailand, the hookworms were prevalent in the southmost region of the country. Association with demographic characteristics and risk behaviors of the two parasites were analyzed and presented in this study. Overall, this countrywide survey provides basic information of the current status of helminth infections in Thailand. Moreover, the data clearly indicates a dramatic reduction of O. viverrini prevalence likely due to extensive control activities under the national campaign against the liver fluke over the past five years.