ABSTRACT
Background: Opisthorchiasis, caused by liver fluke Opisthorchis viverrini is endemic in many countries of the Southeast Asia such as Thailand, Laos PDR, Cambodia and South Vietnam. It is a medically important fluke which causes several hepatobiliary diseases and cholangiocarcinoma. The tegument of O. viverrini is served as the site for sensory input. When the metacercaria infects to human, it excysts and migrates into bile ducts by creeping to pass the hepatopancreatic ampulla. The metacercaria might be equipped with some sensory perceptions. The tegumentary papillae may have a role for sensation. No detail of the ultrastructural of the tegumentary papillae of the O. viverrini has been studied.Objective: To study the ultrastructure of the tegumentary papillae of newly excysted O. viverrini metacercariae by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).Study design: Descriptive study based on morphological observation at the ultrastructureral level.Setting: Department of Anatomy and Department of Parasitology, Faculty of Medicine, Khon Kaen University, Thailand.Materials and Methods: O. viverrini metacercariae obtained from naturally infected cyprinoid fish in endemic area in Khon Kaen were excysted by suspending in 0.1% trypsin solution. The newly excysted metacercariae were processed and observed with a scanning and a transmission electron microscopes. Results: SEM studies of tegumentary papillae identified four types of papillae. Type I was a small conical papilla with long cilium (Fig. 1). Type II possessed short cilium and a larger conical papilla than type I (Fig. 2). Type III was characterized by grouping of 2-3 conical papillae on a dome-shaped base with variable length of the cilia (Fig. 3). Type IV was non-ciliated conical papilla and found solely on inner lip of the oral and ventral suckers (Fig. 4). TEM observation revealed two types of tegumantary papillae, ciliated (type A) and non-ciliated (type B) papillae. Only one cilium was found in all ciliated tegumantary papillae. Based on morphology of tegumentary papillae and ultrastructures of the bulbous ending, the ciliated papillae were further divided into three subtypes (A1, A2 and A3). In type B, there was an elevation of the tegument and the bulbous ending was lack communication with the external surface.Conclusions: As seen by SEM, there were four types of tegumentary papillae of the excysted O. viverrini metacercaria. By TEM observation, only two types of tegumentary papillae, uniciliated and non-ciliated were found. Based on internal structures of the bulbous ending, the uniciliated tegumentary papillae were further divided into three subtypes . The evidence of a nerve process leading to the bulbous ending in the TEM study supported that these tegumentary papillae may consider to serve as a structure for sensory perception. Only the type II papilla in SEM study and uniciliated papilla type A1 in TEM were both located in the outer lip of the oral sucker. Therefore, they might be the same type of papillae.Key words: Opisthorchis viverrini, metaceraria, papillae, SEM, TEM
ABSTRACT
Background: Infection of Opisthorchis viverrini is widely endemic mainly in Northeast of Thailand including Laos, Cambodia and South Vietnam. Its prevalence and pathogenic effects are associated with several hepatobiliary diseases in human. The liver fluke is monoecious, seft-fertilization can be occurred individually. The male reproductive organ usually consists of two deeply lobed testes, located in the posterior region of the body next to the ovary. No description is available on the ultrastructure and development of the testes of the Opisthorchis viverrini.Objectives: This study aims to examine the morphology and ultrastructure of the testes of the adult flukes O. viverrini.Study design: Descriptive study based on morphological observation by using light microscope (LM), transmission electron microscope (TEM) and scanning electron microscope (SEM).Setting: Department of Anatomy and Department of Parasitology, Faculty of Medicine, Khon Kaen University, Thailand.Materials and Methods: The encyst metacercaria of Opisthorchis viverrini were identified and collected. Ten adult Golden Syrian hamsters were used. Each animal was infected with 50 encyst metacercaria by gastric intubation. The animals were then sacrificed by deep ether anaesthesia, at 28 days post infection. The recovered flukes were routinely processed for investigation of the testes by LM, TEM and SEM.Results: In the whole mount specimens, the pair testes of the adult O. viverrini were clearly defined at the posterior 1/3 of the worm body posterior to the ovary. They were multilobate, 4-5 lobes each and located one behind the other. The testes showed numerous germ cells at various stages of development. The spermatogonia were closest to the testicular wall. In the deeper regions, cluster of numerous spermatocytes and spermatids were observed. The early spermatid exhibited an elongated nucleus with exhibiting lamellar chromatin alongside the two sets of striated rootlets. The scanning electron microscopic studied revealed that the spermatozoa were long filiformshaped.Conclusions: This is the first report of the morphology of the testes of the adult flukes, Opisthorchis viverrini studied by using light and electron microscopes. The testes contained different stages of developing spermatogenic cells. Their three dimentional morphology were thread-like with no easily discernible heads and tails.Keywords: Opisthorchis viverrini, spermatogenic cells, testes, ultrastructure