Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 20 1 2025 02 27 111 121 Phuangphet Molee Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand 2. Centre of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand 3. Centre of Excellence in Fungal Research, Naresuan University, Phitsanulok 65000, Thailand Apichat Vitta Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand 2. Centre of Excellence in Medical Biotechnology, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand Somchai Saengamnatdej Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand 2024 07 16 2024 10 23 Background: Helminthic infections cause helminthiasis, including infections by Strongyloides stercoralis, a kind of helminths that cause reinfection and lead to severe infections, can be transmitted through the soil. We aimed to identify S. stercoralis and other helminthic infections in rubber tree plantations in Thailand's lower northern regions. The specific goals include assessing prevalence using Formalin Ethyl–acetate Concentration Technique (FECT) and Agar Plate Culture (APC) and constructing S. stercoralis phylogenetic tree. Methods: Overall, 646 fecal samples from rubber plantation workers in five provinces in northern Thailand were examined using FECT and APC under microscope. DNA from larvae confirmed as Strongyloides spp. by Polymerase Chain Reaction (PCR) was sequenced for phylogenetic analysis. The DNA sequences were also submitted to the GenBank database. Results: Prevalence of helminthic infections was 8.82%, with soil transmitted helminths (STH) prevalence at 6.81%; S. stercoralis accounted for 5.41%, with Ascaris lumbricoides at 0.62%, hookworm 0.46%, and T. trichiura 0.31%. PCR analysis successfully amplified the 18S rRNA gene in 26 out of 34 genomic DNAs, indicating a detection rate of 70.59%. Sequencing of these PCR products identified S. stercoralis strains closely related to those reported in the Republic of Lao, Myanmar, and Japan, suggesting genetic diversity within the species. Conclusion: STH prevalence, predominantly S. stercoralis, highlights public health concerns in rubber plantation areas, necessitating enhanced monitoring and intervention strategies. Phylogenetic analysis of S. stercoralis, revealing a close genetic relationship among strains from various Southeast Asian countries, which underscores potential patterns of transmission and evolutionary relationships in the regions. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/4305 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/4305/1414