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Cat's fluke
Last reviewed: 23.04.2024
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The flat worm of the cat's fluke refers to the class Trematoda Digenea (digenetic trematodes), the subclass Fasciola (fasciola), the family Opisthorchis (opisthorchia). Some classifications refer to the species of this parasite as suborder of Heterophyata (heterophytes).
Sometimes a cat's fluke (Opistorchis felineus) is also called a cat liver or Siberian trematode, although chronic hepatobiliary damage (opisthorchiasis) caused by this helminth is a common infection of fish-eating mammals (including humans) from Eastern Europe to the Asia-Pacific region.
[The structure of the cat's fluke
Types of flukes of opisthorchia, the infection of which leads to the opisthorchiasis, except for the cat's fluke, include the opisthorchia viverrini (Opisthorchis viverrini), common in the countries of Southeast Asia, and Clonorchis sinensis (Chinese fluke). And among the liver flukes, affecting cattle, there are flat worms of similar morphology, like Fasciola hepatica and Dicrocoelium dendriticum.
The structure of the cat's fluke is well studied by parasitologists. The body of the worm is flat, in shape resembles a narrow leaf: the length rarely exceeds 1.5 cm (average, 5-10 mm), and the width varies from 0.7 to 1.6 mm.
The body of the cat's fluke is covered with syncytial epithelium (tegumen), beneath it is the basal membrane, and beneath it is the fibers of smooth musculature. There are two suckers (oral and abdominal); in the oral sucker there is a mouth opening leading to the pharynx, equipped with muscles that provide both absorption of food and the withdrawal of waste products (since the intestine of the worm does not have an opening from the opposite end).
The sex system of the cat fluke is hermaphroditic, that is, the worm has a uterus for eggs, and an ovary, and testes. The oval-shaped eggs of the cat litter are provided with a lid for the exit of the larva.
Life cycle of the cat's fluke
The entire life cycle of the cat's fluke, according to biologists, runs for four to six months. That is, during this time the worm, changing the intermediate hosts, develops from the egg stage to the adult state - marita.
Eggs with miracidia larvae are found in fresh water, where they are swallowed by snails of bithinia - the gastropods of Bithynia leachi, which are the first intermediate host of the cat fluke. In the digestive system of the mollusk, eggs are opened, releasing miracidia, affecting the tissues of the internal organs of the host. This is the first larval stage of the life cycle of the parasite worm.
Then comes the second larval stage: from miracidia a fixed sporocyst is formed in which germ cells are formed. During the third larval stage of these cells parthenogenetic reproduction produces mobile larvae - redia, which feed intensively and multiply. This leads to the appearance of cercariae, which is the fourth larval stage of the cat's fluke. Cercaria larvae leave snails and move freely in the aquatic environment due to the tail appendage that they have, and this stage of parasite development is already invasive (infectious), as the cercariae are looking for a host.
The second intermediate host of the fluke is the carp fish, into which the cercariae penetrate freely (through the gill slits and through the outer covers) and spread throughout the body, primarily in the muscle tissues. Here cercariae continue to grow and pass into the stage of metacercariae (Cyprinus carpio). The tail disappears as superfluous, but after 30-40 days a capsule-type envelope protecting the metacercaria appears.
At this stage, the cat's fluke is ready to move on to its final host - a predatory mammal or human. Once in the digestive tract along with the eaten infected fish, the helmet's metacercariae lose their protective shell (it dissolves the gastric juice into the process of digestion), and the released larvae penetrate into the most suitable place for them - the liver.
Adhering to the liver tissues, metacercariae after a while grow into an adult hermaphrodite stage - ready to lay eggs marite. It is in this form that the cat's fluke parasitizes the liver of a person who has infected a man (often for dozens of years), and the eggs laid with feces fall into the sewage, and then into the water. And the next life cycle of the cat fluke begins.
Ways of human infection with this helminth is the consumption of fish that has not been thermally processed, that is, a little roasted or boiled, dried, salted or cold-smoked.
To date, the risk of infection by this parasite, according to WHO, is really threatened by 80 million inhabitants of our planet.
Symptoms of cat fluke, that is, signs of infection with opisthorchiasis, diagnosis of this parasitic disease, treatment of cat fluke (preparations for the treatment of cat flies and treatment with alternative means), as well as the prognosis of opisthorchiasis and prevention of infection with catnip are detailed in our publication - Opisthorchias.