Clonorchis sinensis

Clonorchis sinensis

<p align="CENTER"><span style="color: #000000;"><span style="font-size: large;"><i><b>Clonorchis sinensis</b></i></span></span><span style="color: #000000;"><span style="font-size: large;"><b> (Cobbold, 1875) Looss, 1907</b></span></span></p> <p align="CENTER"><span style="color: #000000;"><span style="font-size: large;"><b>(Figure 2-38)</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>Clon</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> = branched 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>sinensis </i></span></span><span style="color: #000000;"><span style="font-size: medium;">= representing China.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>SYNONYMS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Distoma sinens</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> Cobbold, 1875; </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Distoma spathulatum</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> Leuckart, 1876; </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Distoma endemicum</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> Jima, 1886. Also, some have included the members of the genus </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Clonorchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> within the genus </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;">.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>HISTORY:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> This trematode was originally described from the bile passages of a Chinese carpenter working in Calcutta, India. It was described in Japan in 1883 and was recognized as being endemic in south China in 1908 by Heanley. Cats were first noted to be infected in Japan (Ijima, 1887).</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>GEOGRAPHIC DISTRIBUTION:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> This fluke is found in Japan, Korea, Taiwan, China, and North Korea. The infection seems to be present in fresh-water fishes surrounding the areas bordering on the China Sea.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>LOCATION IN HOST:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Gall bladder and bile ducts; occasionally in the pancreatic duct or the small intestine.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>PARASITE IDENTIFICATION:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Clonorchis sinensis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> differs from specimens 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;"> in that it has highly branched testes. The highly branched testes separate </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Clonorchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> from the other genera of opisthorchid trematodes. The adults are 10 to 25 mm long and 3 to 5 mm wide. The eggs are yellowish brown with a distinct operculum. There is often a slight protuberance on the end of the egg opposite the operculum. The eggs measure 28 to 35 µm long by 12 to 19 µm wide.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>LIFE CYCLE:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Cats were first used to show that a fresh-water fish intermediate host was a required part of the life cycle (Kobayashi, 1915). About 80 species of fish have been identified as hosts; most of the piscine hosts are in the family Cyprinidae. A few years later, the snail hosts were identified and are now recognized as species of </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Parafossarulus, Bulimus, Semisulcospira, Alocinma,</i></span></span><span style="color: #000000;"><span style="font-size: medium;"> and </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Melanoides</i></span></span><span style="color: #000000;"><span style="font-size: medium;">. The eggs of the </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Clonorchis sinensis </i></span></span><span style="color: #000000;"><span style="font-size: medium;">hatch only if they are ingested by the appropriate snail host.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"> After ingestion of an infected fish, the young trematodes migrates to the bile duct through the ampulla of Vater. It then takes about one month for the trematodes to reach maturity. The trematodes have been found to live as long as 12 years and 3 months in cats (Miyazaki, 1991).</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>CLINICAL PRESENTATION AND PATHOGENESIS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Ultimately the host develops cirrhosis of the liver. The changes in the liver have been divided in humans into three basic stages. The first stage consists primarily of proliferation of the biliary-tract epithelium. In the second stage the surrounding liver tissue is compressed by the growing connective tissue around the bile ducts. In the third stage, there is significant cirrhosis and destruction of the liver parenchyma. It is believed that an infection with only a few flukes will seldom induce more than the first stages of the disease. Similar progression of disease is thought to occur in infected cats.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>TREATMENT:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Praziquantel is likely to prove successful in eliminating these trematodes from many treated cases.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>EPIZOOTIOLOGY:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Cats are a major host of this pathogen. In some areas of China and Vietnam, up to one-third of the feline population might be shedding eggs of this parasite in their feces. In areas where fish are consumed raw, this can have a major impact on the human population by the maintenance of the parasite in the surrounding fish population.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>HAZARD TO OTHER ANIMALS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Dogs and other fish-eating mammals can also be infected with this parasite.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>HAZARD TO HUMANS:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Large numbers of human beings are infected with this parasite in the geographical regions where it is found. Surveys in Korea and Vietnam have found prevalence rates above 15% in some populations (Chung</span></span><span style="color: #000000;"><span style="font-size: medium;"><i> et al</i></span></span><span style="color: #000000;"><span style="font-size: medium;">., 1991; Kieu,</span></span><span style="color: #000000;"><span style="font-size: medium;"><i> et al</i></span></span><span style="color: #000000;"><span style="font-size: medium;">., 1992)</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>CONTROL/PREVENTION:</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Prevent the ingestion of infected raw, dried or pickled fish; these latter methods are not necessarily going to kill the metacercarial stage of the trematode.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>REFERENCES:</b></span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;">Chung DI, Kim YI, Lee KR, Choi DW. 1991. Epidemiological studies of digenetic trematodes in Yongyan County, Kyungpok Province. Kisaengchunghap Chapchi 29:325-338.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;">Ijima I. 1887. Notes on Distoma endemiocum, Baelz. Journal of the College of Science, Imperial University, Tokyo 1:47-59 [Cited in: Grove DI. </span></span><span style="color: #000000;"><span style="font-size: medium;"><span style="text-decoration: underline;">A History of Human Helminthology.</span></span></span><span style="color: #000000;"><span style="font-size: medium;"> CAB Inter, Wallingford, UK]</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;">Kobayashi H. 1915. On the life history and morphology of </span></span><span style="color: #000000;"><span style="font-size: medium;"><i>Clonorchis</i></span></span><span style="color: #000000;"><span style="font-size: medium;"><i>sinensis</i></span></span><span style="color: #000000;"><span style="font-size: medium;">. Centralbl Bakt Parasitenk Infekt 75:299-318.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;">Kieu TL, Bronshtein AM, Sabgaida TP. 1992. Clonorchiasis in the People’s Republic of Vietnam. 2. The clinico-parasitological examination of a focus and a trial of praziquantel treatment. Med Parazitol Mosk 4:7-11.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;">Miyazaki I. 1991. </span></span><span style="color: #000000;"><span style="font-size: medium;"><span style="text-decoration: underline;">Helminthic Zoonoses.</span></span></span><span style="color: #000000;"><span style="font-size: medium;"> 494 pages. International Medical Foundation of Japan. Fukuoka, Japan.</span></span></p> <p align="JUSTIFY"><span style="color: #000000;"><span style="font-size: medium;"><b>Figure 2-38.</b></span></span><span style="color: #000000;"><span style="font-size: medium;"> Clonorchis sinensis from the gall bladder of a cat in China. Note the highly branches testes in the posterior of the body and the restriction of the uterus to between the ventral sucker and the ovary. the vitellaria are not very distinct in this specimen.</span></span></p>