Our body is home to many other living things. And if lactobacilli, which live in our small intestines, benefit a person (participate in the breakdown of complex proteins and even synthesize some vitamins for us), then other organisms may become completely undesirable neighbors. It is to them that digenetic flukes occur, and simply one of the varieties of flatworms. Many of them cause quite dangerous diseases - trematodoses, which can even lead to death. Digenetic flukes as parasites of humans and domestic animals will be discussed in this article.
Systematic position
The class of digenetic flukes (Digenea) has about 7 thousand species and belongs to the type of flatworms (Plathelminthes). In some classifications, they belong to one of the subclasses of flukes or trematodes (Trematoda):
- Monogenic flukes (Monogenea) are mainly external parasites of cold-blooded fish, amphibians and reptiles.
- Aspidogastrea (Aspidogastrea) - external or internal parasites of mollusks.
Although these flatworms lead a parasitic lifestyle, they develop without a change of owners.
- And, in fact, diagenetic flukes are internal parasites (endoparasites) of warm-blooded animals and humans, which are their ultimate owners. That is, an organism in which a parasite reproduces sexually.
Endoparasites and their owners
The class of diagenetic flukes include blood, liver and pulmonary obligate (mandatory) parasites. All of them have complex development cycles with a stage that develops in the intermediate host, and obligatory development in the final host.
A distinctive feature of the structure of diagenetic flukes is a flat leaf-shaped body and the presence of 2 or 3 suction cups, with which a sexually mature parasite attaches to the host tissues. The sizes of parasites vary from microscopic to 30 millimeters. Of the more than 4 thousand species of diagenetic flukes known, about 40 species are parasites, the final owner of which can be domestic animals and humans.
Morphology and physiology
The structural features of diagenetic flukes are associated with their parasitic lifestyle. The following structural features of the body are characteristic of a mature individual:
- Like all flatworms, they lack a body cavity. The outer coverings have a complex structure and are called tegument. In its composition are substances that interfere with the effects on the parasite of the gastric juice of the host.
- The digestive system begins with the mouth opening, where the ring muscles, the suction cups, are located. Through the throat, food enters the stomach, usually branched into 2 parts. There is no anus.
- These cavity parasites do not have respiratory organs and lead an anaerobic lifestyle. This structural feature of the diagenetic flukes is associated with their endoparasitism, although some of the larval stages have organs that provide oxygen.
- Isolation of metabolic products occurs through ciliated cells and ends with holes on the surface of the body.
- The nervous system and sensory organs are not developed or are poorly developed.
- Sexually mature individuals are more often hermaphrodites, although dioecious representatives are also found. The reproductive system is one ovary and two testes.
Of course, this characteristic of diagenetic flukes briefly outlines the general system of their organization.
Complex life cycle
In the cycle of development of diagenetic flukes there is a change of owners. An intermediate host is more often mollusks in the body of which a larva (miracidia with cilia) develops and grows. In the body of the final host, the reproduction of diagenetic flukes occurs sexually. Fertilization can be either cross-fertilization or self-fertilization in the case of an hermaphroditic adult.
A sexually mature parasite lays hundreds of thousands of eggs that enter a body of water or land. Miracidium emerges from the egg, the task of which is to enter the body of the intermediate host. Infection of the final host occurs by eating infected animals (mollusks or freshwater crustaceans).
Liver flukes
These endoparasites live in the liver and bile ducts. From this group, diagenetic flukes of 3 types deserve characteristics:
- Hepatic fluke (Fasciola hepatica) - causes a person's disease of fasciillosis, characterized by hepatic colic. Adult parasites are hermaphrodites, with a fleshy leaf-shaped body, length - up to 3 cm, width - 1.3 cm. Eggs from the liver pass through the bile ducts into the intestines and then into the environment. Once in a fresh water reservoir, miracidium leaves the egg, which is introduced into the body of the cochlea. After several transformations, the caudate larva leaves the body of the cochlea - a circus, which turns into a cyst (adolescari - a fixed form attached to algae) and is able to maintain its viability for a long time. Man and animals become infected by drinking water with adolescari or eating grass with them.
- Chinese hepatic trematode (Clonorchis sinensis) - causes clonorchiasis with symptoms similar to fasciillosis. The life cycle of this parasite is similar to the hepatic trematode, but there are two intermediate hosts - the snail and fish, in the body of which the cercaria turns into a cyst. Man and animals become infected by eating infected fish.
- Feline fluke (Opisthorchis felineus) - causes opisthorchiasis disease. Two-thirds of cases of infection with this parasite occur in the inhabitants of Russia. That is why we will give more detailed information about these trematodes.
Inhabitant of Siberian rivers
Feline fluke is also called Siberian, since the problem of opisthorchiasis is especially relevant for Western and Eastern Siberia and the Dnieper. This hepatic parasite can live in the pancreas and liver of cats, dogs and humans, which become the final owners. In the life cycle of a cat fluke, there are two intermediate hosts - snails and fish (carp, crucian carp, roach, tench, mackerel, bream, asp). The life cycle and stages of development are similar to all hepatic flukes.
Human infection occurs when light-salted, insufficiently thermally processed fish is eaten. In addition, when using a knife, chopping boards when cleaning and cutting river fish, cercariae remain on objects and can be brought to other food products and serve as a source of infection. Surprisingly, the life span of this adult parasite can reach 15-25 years.
Blood flukes
These parasites are called schistosomes and cause schistosomatosis. Representatives of diagenetic flukes that parasitize in the bloodstream:
- Schistosoma haematobium and Schistosoma mansoni are common in Africa.
- Schistosoma japonicum - common in Japan, Taiwan and the Philippines.
An intermediate host is snails. Cercaria penetrates through the skin into the bloodstream of the main host, migrates into the veins of the abdominal cavity, where dioecious parasites multiply sexually, and eggs are laid either in the intestines (Manson and Katayama disease) or in the bladder (Egyptian hematuria).
Pulmonary flukes
These are representatives of the genus Paragonimus, and diseases are paragonimiasis. Pathogens more than 10 species that are found in the Far East, China, the Philippines, Africa and Central and South America.
There are two intermediate hosts - mollusk and crustaceans (crayfish and crabs). The final host is warm-blooded animals and people who ate infected crustaceans. In the body of the final host, trematodes are localized in the bronchi, where they form fibrous capsules. They can migrate to the lungs and even to the brain.
Biological stability of trematodes
Such complex life cycles lead to mass death of larvae. In addition, clear selectivity in the choice of an intermediate host, and sometimes two, also does not contribute to the biological progress of the species. However, the narrow specialization and degradation of some vital functions, the long-term stability of the larval stages and cysts in the external environment, and in most of the rather long life span of the parasite, have been supporting the evolution of trematodes for millions of years. In addition, an adult trematode produces hundreds of thousands of eggs. It is such a high fecundity that preserves these parasites as a biological species.
Symptoms of trematode infection
The body of the main host responds to infection with parasites intoxication to poisons secreted by worms and allergic reactions to their toxins. It is worth visiting a doctor if at least one symptom of the following appears:
- General breakdown, weakness and drowsiness without visible physical exertion.
- An increase in body temperature over a long period.
- The appearance of allergic reactions - urticaria or itching.
- Enlarged liver, spleen and abdominal pain.
- Long-term disorders of the gastrointestinal tract.
- Jaundice of the skin and weight loss.
The incubation period of most trematodoses is 90-120 days from the time of infection. And just such a period needs to be analyzed to identify pathways of infection with parasites.
Diagnosis and treatment of trematodoses
The main diagnostic method is the study of feces for the presence of trematode eggs. In addition, a general biochemical blood test for the presence of liver enzymes can be performed. To diagnose pulmonary flukes, a lung x-ray and sputum analysis are performed. If there is a suspicion of schistomiasis, a urinalysis is prescribed, where the type of fluke is diagnosed by the identified eggs.
Timely treatment will not allow the development of chronic forms of helminthiases. In treatment, the main direction is the use of antiparasitic drugs, depending on the type of pathogen. When opisthorchiasis apply "Praziquantel", "Caesol", "Dronit." At clonorchosis - "Akrikhin". For the treatment of fasciillosis, Chloxyl is used, and for paragonimiasis, Biltricid is used.
After deworming, rehabilitation and rehabilitation therapy is required depending on the degree and localization of the affected organs. However, it is worth remembering that the medicine should be selected exclusively by the doctor. Self-medication in this case can not only not give a result, but also lead to the most negative consequences. Trematodes are dangerous parasites, and it is important to detect their presence in time and begin timely and adequate treatment.
What does traditional medicine advise
In folk practice, there are several recipes for controlling trematodes. But it is necessary to approach their use with caution, since most of them are based on natural poisons, which, if used carelessly, can lead to poisoning. In addition, before using folk remedies, you must consult a doctor.
To get rid of these parasites, traditional medicine advises taking wormwood in the form of tincture, which is sold in pharmacies. It should be taken 3 times a day for a teaspoon. Combine with the adoption of laxatives.
Another effective remedy is dry coriander seeds. They are taken for 8 days according to the scheme - 0.5 grams on the first day, 1 gram - on the second, and 1.5 grams - the rest of the days. According to the same scheme, you can take dry flowers of black cloves.