Comparative studies on the morphology of the eggs of Opisthorchis viverrini and lecithodendriid trematodes.

Iodine staining and scanning electron microscopy were used to determine the morphological features distinguishing Opisthorchis viverrini from lecithodendriid eggs in human feces. The embryonated eggs of lecithodendriid trematodes differ from O. viverrini by the presence of an iodophilic body, a large mass at the posterior end of miracidium that stains brown in 0.2% iodine solution and the curved miracidium of Phaneropsolus bonnei. All forms of lecithodendriid eggs can be differentiated from those of O. viverrini by a set of morphological features of the shell surface, the knob, the operculum, the shoulder, the shape and size. On the basis of these differences, it is possible to perform differential egg counts.

Eggshell morphology of the small eggs of human trematodes in Thailand.

Light and scanning electron micrographs of Opisthorchis viverrini, Haplorchis taichui, H. pumilio, A Phaneropsolus bonnei, and Prosthodendrium molenkampi eggs were studied. Under light microscopy. O. viverrini eggs had rough eggshells and prominent shoulders. H. taichui, H. pumilio were similar in shape and had smooth eggshells and prominent shoulders. H. pumilio eggs were bigger than H. taichui eggs. P. bonnei and P. molenkampi eggs had smooth eggshells and indistinct shoulders. P. bonnei eggs were thinner and bigger than P. molenkampi eggs. Some deformed eggs of O. viverrini and Haplorchis sp. were found and they had no embryos and indistinct opercula. Under scanning electron microscopy, O. viverrini eggs looked like musk-melon skin; they had prominent shoulders and long knobs. H. taichui eggs had curly, thread-like ridges and prominent shoulders and knobs. H. pumilio eggs had streched ridges, like Chinese bitter mormodica, and prominent shoulders. P. bonnei and P. molenkampi eggs had smooth eggshells and small shoulders and knobs.

Influence of water current on the distribution of Opisthorchis viverrini infection in northeastern villages of Thailand.

The prevalences of Opisthorchis viverrini infection in the villages on the banks of rivers and those far from the rivers were studied in Loei and Nong Khai Provinces in Thailand. Most of the people examined in the present study were agriculturalists. The overall prevalence of O. viverrini infection was 41.3%. The prevalence of infection in males and in females in the villages far from the rivers were 52.6% and 51.7%, respectively, while the percent of people in the villages on the banks with infection were 27.9% and 21.7%, respectively. Prevalence of infection among the people residing far from the rivers was higher than those residing on the banks. This was observed despite the higher recording of raw fish consumption in villages on the banks. Infection level increased sharply in the age-group 6-10 years old among people residing far from the rivers. High prevalences of infection were observed in age groups from 11 to 50 years. Both types of villages had a similar proportion of houses with sanitary latrines.

Scanning electron microscopy of adult Echinostoma malayanum.

Scanning electron microscopy observations of E. malayanum adult obtained from small intestines of infected rats was made. The number of collar spines were 41. The features observed were a pair of corner spines (3 oral and 2 aboral) total 10; a pair of lateral collar spines (10 spines each side); total 20; dorsal collar spines (5 oral and 6 aboral) total 11. Sensory papillae were found more densely situated on the circumoral disc around the oral sucker and on the ventral sucker. Other sensory organs, dome shaped, found only on the circumoral disc. The scales appear mainly on the ventral surface. The microvilli are present on the tegument where the scales occur, while the other part of dorsal side had pitted tegument.