Opisthorchiasis is endemic in parts of Southeast Asia, including the northern and northeastern regions of Thailand. In these regions, the transmission by fish intermediate hosts has received little attention. We investigated the intensity of Opisthorchis viverrini metacercariae (OV MC) in wild cyprinid fishes from five districts within the Nakhon Phanom Province, Northeast Thailand. Fishes were procured from local markets in five districts throughout three different seasons (hot, rainy and cold) between February 2018 and January 2019. The samples were identified, counted and weighed before metacercariae detection was performed via the artificial digestion method. A total of 2,149 freshwater fishes, representing 20 species were collected. The fish most commonly contaminated with OV MC were Anematichthys repasson and Hampala dispar. The intensity of OV MC in Nakhon Phanom was 0.23 OV MC/fish and varied among districts, ranging from 0.07 to 0.52. A low intensity of OV MC/fish (defined as <=1 cyst) was found in all three different seasons in the Nakhon Phanom Province; hot season (0.55), cold season (0.22) and the rainy season (0.13). The intensity of OV MC/fish was moderate (defined as >1 cyst) in the Renu Nakhon district (2.5) in the hot season. By fish species, H. dispar yielded the highest, with a moderate intensity of 2.1. In natural freshwater cyprinid fish in Nakhon Phanom, OV MC infection is endemic with intensity rates varying according to district, season and fish species.
Helminth infections (HIs) are an important public health problem in tropical countries, and the associated problems have been neglected in rural areas of Thailand. Therefore, this study reports the prevalence and intensity of HIs among inhabitants of the Khon Sawan district, Chaiyaphum province, and Kaeng Samnam Nang district, Nakhon Ratchasima province, which are located near the Chi River and Lahanna water reservoir, northeastern Thailand. A cross-sectional descriptive study was conducted between July 31, 2018, and June 30, 2019, among rural villagers from 40 rural villages in 4 subdistricts. The participants were selected from the village enrolment list after proportional allocation of the total sample size. Faecal samples from 691 inhabitants were prepared using solvent-free faecal parasite concentrator, and helminths were then detected using a light microscope. Statistical analysis included the Chi-square test with Yates correction, and multivariable logistic regression was performed. A P-value of <0.05 was considered statistically significant. The prevalence of HIs was 2.03%. The most prevalent helminths were Opisthorchis viverrini (1.31%), followed by Strongyloides stercoralis (0.44%), Ascaris lumbricoides (0.29%), hookworm (0.15%), Teania spp. (0.15%) and one minute intestinal fluke (0.15%). Coinfections were identified in 2 cases for S. stercoralis and hookworm and 1 case for O. viverrini and S. stercoralis infection. All infected participants had a light intensity of HI. There was no significant difference between general characteristics for all HIs. The prevalence of HIs was not significantly associated with general characteristics. This study indicates that the infections result mainly from foodborne helminths and skin-penetrating nematodes. Therefore, interventions should concentrate on the personal hygiene of the population and improving sanitation to reduce HIs in this area.
Opisthorchiasis caused by Opisthorchis viverrini infection is a major public health concern in Thailand. Despite many decades of national campaigns in place to reduce and control opisthorchiasis in Thailand, the infections remain to exist particularly in the northern and northeastern parts of the country. This study aimed to evaluate the current prevalence of O. viverrini infection in rural communities in northeast Thailand. A cross-sectional survey was conducted between February and October 2018 in three districts (Na Kae, That Phanom and Wang Yang) in Nakhon Phanom Province, Thailand. Demographic data were collected using a standardised questionnaire. Stool samples were collected and processed using the Kato-Katz technique to determine the presence of O. viverrini and other intestinal parasites. In total, 564 individuals were enrolled. The overall intestinal helminth infections were 15.2% (95% CI: 12.4-18.5). Species distribution included a majority of O. viverrini mono-infections (12.9%), followed by Strongyloides stercoralis (1.4%) and Taenia spp. (0.4%). The prevalence of O. viverrini was significantly higher in Wang Yang district (P = 0.022), in males (P = 0.004) and those previously positive with helminth infections (P<0.001) and received treatment of anti-helminths (P<0.001), than in their counterparts. Multivariate regression analysis revealed that being male (adjusted odds ratio [aOR] 1.77, P = 0.035) and those who previously tested positive for helminth infections (aOR 8.69, P<0.001) were significantly associated with a higher odd of O. viverrini infections, but lower in those who had previous stool examination (aOR 0.22, P = 0.001). This study demonstrated that the updated prevalence of O. viverrini infection is still high in rural communities in northeast Thailand. The data of this study will be useful to guide and improve strategies for future O. viverrini and other helminths prevention and control in this region.