Faecal examinations for helminth eggs were performed on 1869 people from two
riverside localities, Vientiane Municipality and Saravane Province, along the
Mekong River, Laos. To obtain adult flukes, 42 people positive for small
trematode eggs (Opisthorchis viverrini, heterophyid, or
lecithodendriid eggs) were treated with a 20–30 mg kg−1 single dose
of praziquantel and purged. Diarrhoeic stools were then collected from 36 people
(18 in each area) and searched for helminth parasites using stereomicroscopes.
Faecal examinations revealed positive rates for small trematode eggs of 53.3%
and 70.8% (average 65.2%) in Vientiane and Saravane Province, respectively.
Infections with O. viverrini and six species of intestinal
flukes were found, namely, Haplorchis
taichui, H. pumilio, H.
yokogawai, Centrocestus caninus,
Prosthodendrium molenkampi, and Phaneropsolus
bonnei. The total number of flukes collected and the proportion of
fluke species recovered were markedly different in the two localities; in
Vientiane, 1041 O. viverrini (57.8 per person) and 615 others
(34.2 per person), whereas in Saravane, 395 O. viverrini (21.9
per person) and 155207 others (8622.6 per person). Five people from Saravane
harboured no O. viverrini but numerous heterophyid and/or
lecithodendriid flukes. The results indicate that O. viverrini
and several species of heterophyid and lecithodendriid flukes are endemic in
these two riverside localities, and suggest that the intensity of infection and
the relative proportion of fluke species vary by locality along the Mekong River