Surveillance of the impact on the spread of parasitic infections in intermediate hosts at the Mae-Soi Watergate Project, Chiang Mai Province, 2020

Abstract

Mae-Soi Watergate Project is a developmental project of water resources for agricultural purposes in the Ping River basin, the lower part of Chiang Mai and Lamphun provinces. It is a part of the impact assessment and environmental health protection plan by the Department of Irrigation. The purpose of this study is to investigate the prevalence of parasitic infections in the intermediate in the natural environment including freshwater fish and snails in the Ping River area on the Chiang Mai and Lamphun provinces' sides. The study covered 9 villages, affecting a total of 12,101 people, carried out in 2020.

The detection of eggs, and larval stages of parasites in human feces using the Formalin-ethyl acetate concentration technique (FECT) in 177 randomly selected samples showed that the samples were infected with two types of parasites: Opisthorchis viverrini-like at 7.91% and Strongyloides stercoralis at 2.82%. Co-infection of both parasitic types in the same individual was observed at 1.13%. Additionally, two types of protozoa, Blastocystis hominis at 1.69% and Giardia lamblia at 0.56%, were also detected. The study of intermediate hosts of Opisthorchis viverrini-like from the examination of metacercarial infection in freshwater snails using the digestion method showed that out of 1,098 snail samples, 134 were found to be infected with the parasites, with an infection rate of 12.2%. Similarly, the study of metacercarial infection in freshwater fish found that 9 fish species were infected with these parasites. The study also investigated the presence of larval-stage parasites in the feces of domestic animals such as dogs, cats, cows, and buffaloes using the FECT method. Out of 200 samples, 89 animals were found to be infected with parasites, constituting 44.50% of the examined samples.  

In summary, this study identified multiple parasitic infections in both the human population and semi-domestic hosts in the Mae Soi Watergate Project. Opisthorchis viverrini-like is a significant health concern in the region due to the consumption habits and natural environmental conditions. These findings emphasize the importance of continued monitoring and data sharing to prevent the spread of these parasitic infections after the project's completion.