Tegumental and excretory-secretory proteins are reported as diagnostic antigens for human opisthorchiasis. Rhophilin associated tail protein1-like (OvROPN1L) protein of Opisthorchis viverrini sperm tail showed potential as a diagnostic antigen. The OvROPN1L recombinant fragments were assayed for diagnostic antigenicity for human opisthorchiasis using indirect ELISA. The strongest antigenic region was a N-terminus peptide of M1 - P56. One synthetic peptide (P1, L3-Q13) of this region showed the highest antigenicity to opisthorchiasis. Sera from other parasitic infections including Strongyloides stercoralis, hookworm, Taenia spp, minute intestinal flukes, Paragonimus spp showed lower reactivity to P1. Peptide P1 is located in the disordered N-terminus of ROPN1L supporting its suitability as linear epitope. In the Platyhelminthes the N-terminal sequence of ROPN1L is diverging with taxonomic distance further suggesting that peptide P1 has potential as diagnostic tool in the genus Opisthorchis/Clonorchis. It should be further evaluated in combination with peptides derived from other O. viverrini antigens to increase its diagnostic power.

During the mobile clinic activities in Tak Province, Thailand, Paragonimus sp. eggs were found in a fecal sample of a 72-year-old Karen resident. Paragonimus DNA was amplified from the stool sample and identified to P. heterotremus. The patient did not have any symptoms. Apparent pulmonary lesion was not found on the chest X-ray. The patient admitted habitual consumption of semi-cooked or roasted waterfall crabs for several years. The waterfall crabs collected from stream near the village were found negative for Paragonimus metacercariae. In northern Thailand, paragonimiasis remains as one of the public health concerns and should be ruled out for asymptomatic pulmonary patients.