Opisthorchis viverrini

Opisthorchis viverrini

<p align="CENTER"><span style="color: #000000;"><span style="font-size: large;"><i><b>Opisthorchis viverrini</b></i></span></span><span style="color: #000000;"><span style="font-size: large;"><b> (Poirier), 1886) Stiles and Hassall, 1896</b></span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>ETYMOLOGY:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Opistho </i></span></span><span style="color: #000000;"><span style="font-size: medium;">= posterior and </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>orchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> = testis along with </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>viverrini </i></span></span><span style="color: #000000;"><span style="font-size: medium;">= representing the host from which it was originally described </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Felis viverrus</i></span></span><span style="color: #000000;"><span style="font-size: medium;">.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"> The adult </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Opisthorchis viverrini</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> is morphologically very similar to and almost indistinguishable from </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Opisthorchis felineus</i></span></span><span style="color: #000000;"><span style="font-size: medium;">; there are, however, morphological differences in the larval stages. This trematode is a common problem in Thailand, where in some villages infections in human populations may be as high as 94% (Upatham ES, Viyanant V, Kurathong S, Brockelman WY, Menaruchi A, Saowakontha S., Intarakhao C, Vajrasthira S, Warren KS. 1982. Morbidity in relation to intensity of infection in opisthorchiasis viverrini: study of a community in Khon Kaen, Thailand. Am J Trop Med Hyg 31:1156-1163.). The infection also occurs in Laos, Malaysia, and India. In Thailand, cats are found infected with this parasite even in areas where human infections are uncommon (Sadun EH. 1955. Studies on </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Opisthorchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>viverrini</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> in Thailand. Am J Hyg 62:81-115.); in 1965, 60% of cats sampled in the northeastern part of the country were infected. The second intermediate host is a fresh-water fish, and the infection is obtained by eating raw fish. Infections in humans have led to carcinoma of the bile ducts (Wykoff DE, Chittaysothorn K, WInn MM. 1966. Clinical manifestations of </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Opisthorchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>viverrini</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> infections in Thailand. Am J Trop Med Hyg 15:914-918.). Fecal examinations have shown that infected cats shed from 358 to 3,509 eggs per adult worm per day; sixteen naturally infected cats were found to harbor an average of 99 worms per cat (Wykoff DE, Ariyaprakai K. 1966. </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Opisthorchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>viverrini</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> in Thailand - Egg production in man and laboratory animals. J Parasitol 52:631).</span></span></p>