It is often difficult to distinguish
between these trematode species using morphological methods due to the similarity of their eggs
and larval stages both in mixed and co-infections. A sensitive, accurate, and specific detection method of
these flukes is required for an effective epidemiological control program. This study aimed to determine
the prevalence of O. viverrini and H. taichui infections in human feces by using formalin–ether sedimentation
and high annealing temperature random amplified polymorphic DNA (HAT-RAPD) PCR methods. Fecal specimens
of people living along the Mae Ping River, Chomtong district were examined seasonally for trematode
eggs using a compound microscope. Positive cases were analyzed in HAT-RAPD, DNA profiles were compared
with adult stages to determine the actual species infected, and specific DNA markers of each fluke were also
screened. Our results showed that out of 316 specimens, 62 were positive for fluke eggs which were preidentified
as O. viverrini and H. taichui. In addition, co-infection among these two fluke species was observed
from only two specimens. The prevalence of H. taichui infections peaked in the hot-dry (19.62%), gradually
decreased in the rainy (18.18%), and cool-dry seasons (14.54%), respectively. O. viverrini was found only in
the hot-dry season (6.54%). For molecular studies, 5 arbitrary primers (Operon Technologies, USA) were individually
performed in HAT-RAPD-PCR for the generation of polymorphic DNA profiles. The DNA profiles in
all 62 positives cases were the same as those of the adult stage which confirmed our identifications. This
study demonstrates the mixed infection of O. viverrini and H. taichui and confirms the extended distribution
of O. viverrini in Northern Thailand.