Opisthorchiasis

OPISTHORCHOSIS, opisthorchosis, a liver disease caused by the trematode Opisthorchis felineus (Rivolta, 1885) (synonym: Distomum sibiricum Winogradoff, 1892). First discovered in humans by Vinogradov in Tomsk. Opisthorchis felineus is a

representative of the family Opisthorchidae, has a leaf-shaped body that narrows more towards its anterior part, 8–13 mm long and 1.2–2 mm wide. The ventral sucker (Fig. 1) is somewhat smaller than the oral sucker, which reaches 0.25 mm in diameter. A characteristic feature is the location in the posterior part of the body of two lobed testes (6), between which the excretory canal (7) winds in an S-shape, opening at the posterior end of the body. Anterior to the testes lie the seminal receptacle (4) and then the ovary (3); further anteriorly, winding between the blindly ending intestinal loops (5), are the loops of the uterus (2), occupying the middle part of the parasite. At the same level, but outward from the intestinal loops, lie the racemose vitellaria (2). The genital openings (male and female) lie anterior to the ventral sucker; furthermore, towards the male [opening] is directed a powerful, winding vas deferens (6). The eggs are very delicate, pale yellow, provided with a lid, and at the opposite pole with a small cone-shaped thickening of the shell (Fig. 2). Their dimensions are 0.026–0.030 mm × 0.010–0.015 mm. The development of the parasite proceeds with two intermediate hosts, of which the first has not been precisely established; mollusks of the genus Dreissena and Lymnaea stagnalis are suspected. The second intermediate host consists of various species of freshwater fish: roach, ide, tench, rudd. Infection of the definitive host occurs upon eating raw, or weakly boiled and fried, salted or smoked fish invaded by metacercariae of Opisth. felineus. Definitive hosts besides humans include the cat, dog, pig, and some other mammals. Opisthorchis felineus is distributed across certain river basins of both the European and Asian parts of the USSR. This parasite is especially frequent in Siberia, where the Ob River basin represents a major focus of the spread of opisthorchosis among humans and animals. Thus, according to data from the 70th All-Union Helminthological Expedition (K. I. Skryabin and V. P. Podyapolskaya), the Voguls on the Northern Sosva River are infected on average at 89%, and adults even at 96%; the small northern nationalities (Ostyaks, Zyryans) in the region of Obdorsk and others are infected with approximately the same intensity. Workers (Russians) of the Tobolsk and Oksarsk (Obdorsk region) canning factories are infected at 86%. All the mentioned population groups are infected by eating fish in a raw state. In these same regions,

domestic carnivores are also very widely and intensively infected. In the upper reaches of the Ob River on the Tom River (Tomsk) and in the Omsk region, opisthorchosis is also widespread in humans, though to a lesser extent. From other regions of the USSR, opisthorchosis has been established in the basin of the Northern Dvina, in the North Caucasian Territory, in the lower reaches of the Volga, in the Kazakh SSR, and in Kharkov. Besides the USSR, this disease is also found in Romania, northern Germany, Holland, France, the Scandinavian Peninsula, Hungary, Italy, and Japan. The localization of the parasite is the bile ducts of the liver, the gallbladder, and somewhat less frequently the pancreas. It is found in quantities from several specimens to several thousand. According to Askanazy, who worked extensively in this field, pathological anatomy establishes cholangitis; the expanded bile ducts are filled with parasites and their eggs, surrounded by mucus. The histological picture consists of glandular proliferation of the walls of the bile ducts, cellular infiltration, partially by eosinophils. Analogous phenomena occur in the pancreatic ducts, where hemorrhages and necrosis are also established. Later, cirrhotic processes and connective tissue growths develop in the liver, in some cases atypical and finally cancerous neoplasms originating from the epithelium. Vinogradov established loose concrements in the gallbladder with trematode eggs in the center, upon which cholesterol crystals and bile pigments were deposited.

The clinical presentation of opisthorchosis has still been poorly studied. With insignificant invasion, clinical phenomena may apparently be completely absent. With more intensive invasion, constant dull pains in the region of the liver and stomach are noted, sometimes passing into severe pains in the right hypochondrium; usually there is a decrease or absence of appetite (rarer its increase), sometimes stool disturbances; a yellow coloration of the sclerae or more rarely a more sharply expressed jaundice is established; sometimes ascites. In some cases, opisthorchosis may proceed under the picture of chronic recurring cholecystitis. Diagnosis of opisthorchosis can be established precisely only by finding eggs of Opisthorchis felineus in the excrements or in bile obtained from the duodenum by sounding with a thin tube. In weaker invasions, the latter method is the most reliable. Therapy of opisthorchosis is not developed, and there is as yet no remedy that reliably kills Opisthorchis felineus. The best of the remedies tried for opisthorchosis is emetine. With its help, it is possible to achieve both a reduction in the number of eggs in the bile and sometimes a significant improvement in the general condition of the patient. Sometimes for a rather long period of time after treatment, eggs of Opisth. felineus (Fig. 2) cannot be detected either in the excrements or in the bile. However, neither the persistent disappearance of eggs nor the complete disappearance of all clinical phenomena can usually be achieved. Dosage of emetine: 3 cm³ of a 2% solution of emetine hydrochloride subcutaneously for 3 days in a row. After three-day intervals, repeat again. Treatment is prolonged. Prophylactic measures must be reduced to broad sanitary-helminthological education and the protection of water bodies from contamination by the feces of humans, dogs, cats, and pigs. The aforementioned animals must not be fed raw fish. For personal prophylaxis, the consumption of fish as food must be carried out exclusively after thorough thermal processing.

Author signatures:

V. Podyapolskaya