Opisthorchiasis is dangerous for its negative consequences and when infected with it many infectious diseases are much more difficult. Larvae and adult parasites feed on the mucous membrane, epithelium and blood, so they are also called hepatic trematodes. The insidiousness of these parasites lies in the fact that their toxic effect first passes asymptomatically and only after the defeat of various organs with the development of characteristic symptoms, a person can learn about helminthiosis.
Opisthorchiasis is a natural focal disease and a person becomes infected with the use of fish invaded by opisthorchia larvae. Fish of the carp family are the main carriers of helminthiosis. Two types of opisthorchia are causative agents of helminthiosis, of which the Siberian fluke spreads opisthorchiasis in the European part of Russia, in Western Siberia and eastern Kazakhstan. Spread the disease in the countries of South-East Asia parasites of the species O. Viverrini.
Endemic areas of distribution of opisthorchiasis
Distribution of opisthorchiasis is recorded in basins of large rivers. The largest centers of spread of helminthiosis are:
- basin of Ob and Irtysh;
- basin of the Dnieper River, including Don;
- Volgo-Kama basin.
A much lower intensity of opisthorchosis is observed in the basins of the Neman and the Northern Dvina. According to recent research, at least 85% of the total population living near the Irtysh and Ob are invaded by opisthores. In this case, a significant role in the spread of helminthic invasion is played by the national traditions of eating fresh fish from fresh fish.
In the second most endemic area of the disease, in terms of prevalence in the settlements on the Vorkla River, the Seimas, the population is infected with 20 to 80 percent of all residents. In general, the degree of defeat of helminthic invasion in this area of opisthorchosis differs very much depending on the place of residence and ranges from 0.2% in the Poltava region of Ukraine, to 26% in the Golopristan district of the Kherson region.
In some parts of the Perm region of the Volga-Kama basin, the degree of invasion of the population reaches 60 percent. Extensive foci of the disease are registered in Kazakhstan in numerous lakes and tributaries of the Sary-Su River and the rivers Uil and Temir. The carriers of opisthorchiasis in endemic areas are animals that feed on fish, and the person becomes infected when visiting epidemic regions.
It is very easy to infect parasites in the site of helminths. The larvae of the parasites present in the muscles of the invaded fish, when it is cut, remain on the blade of the knife, the cutting board. Later they can seed other products. It is possible to infect humans if they have not washed their hands thoroughly after contact with fresh fish. To avoid infection, it is necessary to take into account that for the destruction of larvae a temperature of 120 degrees is required and heat treatment for 40 minutes. The death of the opisthorch in the saline environment occurs in 20 days, and at a high concentration of salt - in a week.
Features of the development of the worm through the mandatory intermediate stage in the body of fish, require special attention to prevent the penetration of the parasite larvae into the human body. Moreover, according to research, almost all fish in the outbreaks of opisthorchiasis are infected parasites and the infection rate reaches 95%.The density of affection with cercariae is from one to five larvae per one square centimeter of the body surface of each individual specimen.