Schistosomes

Schistosomes are parasites from a group of flatworms or trematodes, also called blood flukes. This is one of the most harmful trematodes because of possible complications, therefore it is very important to identify the pathogen in time and to conduct treatment.

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Features of the structure and life cycle of different species of schistosomes

Schistosomes belong to the trematode class, which characterizes them as individuals with a complex life cycle. They have several hosts and their life cycle takes place with the participation of freshwater mollusks. These are different sexes, but they have the ability to merge at some point and the male wears a female on her body. Therefore, the structure of the male is such that it is slightly smaller than the female in length, but it is thicker. The female has a long, flat body. She after the confluence is in a special bag of a male - a gyneco-channel. The causative agent is also called the blood schistosome because of the primary localization in the blood vessels of the human body.

There are several types of schistosomes that are pathogenic to humans.

Schistosome Mansoni is a parasite that causes the intestinal form of schistosomiasis. It is characterized by the defeat of veins or venules of the intestine, mainly mesenteric vessels. This leads not only to mechanical violations of the intestinal wall, but also to a toxic effect on the work of the intestine. Therefore, the peculiarity of this type of schistosome is the predominance of intestinal symptoms.

Genitourinary schistosoma or schistosoma hematobium is the causative agent of schistosomiasis of urogenital localization. This species has a body covered with spines, which allows it to fix itself for the mucous membrane and withstand the action of urine. This parasite is located in the veins of the small pelvis - the veins of the uterus, the bladder, and also has a high mutagenicity. It causes symptoms that are characteristic for the localization of the pathogen - impaired urination and sexual function, as well as violations of menstrual function.

The Japanese schistosome is also the causative agent of the intestinal form, but it has a more severe course and is widespread in the areas of Indonesia, Japan and China. A feature of the pathology is the rapid course and progression of the disease, which can cause a rapid deterioration of the condition and a progressive impairment of liver function up to cirrhosis.

The size of a male schistosome is about ten to fifteen centimeters, and females are more than twenty centimeters. They live separately for several months, then they unite and the male wears the female for the rest of her life. Males have a sucker, with which they can be fixed to the inner wall of the vessel and actively move around.

The life cycle of the parasite begins with the fact that the eggs that the sexually mature female produces are released into the environment with feces or urine. For further development, they must enter fresh water, where their intermediate host is located. Eggs are swallowed by mollusks of different genera, where further development and formation of larvae takes place. Larvae of schistosomes emerge from the mollusk and they are able to actively swim in the pond.

Ways of infection with schistosomes are contact. They penetrate the human body when swimming in a pond, even through clothing, as well as by accidentally swallowing water or deliberately drinking water. Further after entering the human body, the larva penetrates into the vessels and actively migrates through the body. The place of the final localization of the parasite depends on the type of pathogen and its troposphere is determined by tropism to certain organs. Then, after activation of certain organs in the veins, the parasite can live up to forty years, while a toxin is released and the corresponding symptomatology manifests itself. There are also local manifestations due to damage to the organ wall and disruption of its trophism and venous outflow.

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Symptoms of schistosomiasis infection

The clinical symptoms of schistosomiasis infection can be divided into several stages - the prehepatic, hepatic and posthepatic. The incubation period is from three to six weeks. When the larva enters the human body, it enters the liver at the stage of the larva from the intestine or from the vessels of the skin. This is the prehepatic stage of parasite development. If the schistosome gets through the skin, then at the point of penetration there is a spotting, itching, burning in this area.

Further at the penetration stage, there may be an allergic reaction throughout the body in the form of a rash on the skin of a polymorphous, type of hives. The acute period of the disease, which corresponds to the migration of the parasite through the venous vessels of the body, is characterized by nonspecific manifestations in the form of an increase in body temperature, pain in the muscles and joints, and sleep disorders.

In the hepatic stage in the portal vein system, the parasite grows and multiplies, which corresponds to the next stage of development. The post-hepatic stage of development is characterized by further migration of the male to the female and localization in the pelvic vein system. This corresponds to the stage of widespread invasion, in which the parasite mature is actively moving directly into the organs and lay eggs.

Further, two weeks after the onset of the disease, specific symptoms from the intestine or urogenital system may already appear.

Symptoms from the genitourinary system arise due to the pathogenic action of the schistosome. Mechanical action occurs when the eggs are damaged by the walls of the urino-genital organs - while on the mucous membrane of the bladder, erosions, ulcers, signs of inflammation and polyposic reactions are observed due to prolonged parasitism. There is also a toxic-allergic effect due to the permanent functioning of the schistosome and the release of metabolic products into the human blood. Violated trophic processes of the bladder, uterus, which causes violation of cell division and is a risk factor for the development of oncopathology. The parasite also feeds on erythrocytes and nutrients, which significantly disturbs the overall trophism of the human body and the respiratory function of the blood.

In this case, there may also be general symptoms during the migration of the parasite and its localization in the lungs - there appears a seizure cough, shortness of breath, and shortness of breath. These symptoms pass when the parasite is sent to its final location of localization. Local symptoms, mainly manifested in the form of violation of urination, pain during urination, as well as hematuria (the appearance of blood in the urine). If the schistosome is located in the veins of the uterus or in the ectopic space, then there may be pains in the lower abdomen that are not associated with menstruation, violations of the menstrual cycle.

In chronic conditions, complications often occur - ureteric stricture, pyelonephritis, hydronephrosis, and the formation of stones in the kidneys and bladder. Schistosomes can cause early impotence.

Schistosome Mansoni when ingested in the acute stage also has similar symptoms of general intoxication, muscle pain and skin rash. Further, taking into account its localization, symptoms of dyspepsia will be expressed. First, clinical manifestations in the form of abdominal pain, stool disorders by type of diarrhea. Then, with an increase in the number of parasites and eggs, there is a strong mechanical irritation and this leads to diarrhea alternating with constipation, there may be secretion of mucus and blood in the feces. There are tenesmus and this can lead to bleeding and even to the prolapse of the rectum.

Japanese schistosome is characterized by intestinal symptoms, which have a strong pronounced course with predominant liver damage. This breaks the structure of hepatocytes, which leads to a rapid development of liver cirrhosis. Therefore, along with the intestinal manifestations, there are also symptoms in the form of an increase in the liver, its painfulness upon palpation, yellow sclera and skin.

Diagnosis of schistosomes

Diagnosis of schistosomiasis is much simplified in case there are epidemiological data on swimming in the pond or on contact with the source of infection. The data of the anamnesis allow to reveal the first symptoms of pathology and to study the course of the disease.

The analysis on schistosomes is carried out taking into account the localization of the pathological process. If the patient complains of the genitourinary system, then a microscopic urine test should be performed - the eggs of the schistosome are detected. With ovoscopy, you can see the eggs of the schistosomes, which have an oval shape, elongated, on one side are thorns. With instrumental methods, there is sometimes a need for cystoscopy. In this case, one can see erosion on the inner mucosa of the bladder, signs of inflammation. In biopsies, you can determine the pathogen itself, its eggs, as well as signs of violation of the integrity of the wall.

With intestinal schistosomiasis, the diagnosis can be confirmed by examining stool and microscopy of stool. If there are signs of mucus and blood in the feces, then perform a sigmoidoscopy that allows you to examine the intestinal mucosa and make a biopsy. In biopsies, it is possible to identify the pathogen or its eggs, which makes it possible to exclude autoimmune lesions of the intestine (ulcerative colitis). Be sure to conduct a general blood test. Specific changes that may indicate a helminthic invasion are the eosinophilia of the blood. This indicates the activation of the allergic link of immunity. In the biochemical analysis of blood, there may also be changes in the acute stage in the form of increased hepatic enzymes (alkaline phosphatase), as well as hyperbilirubinemia of mixed origin, especially if it is a Japanese schistosome that affects the liver.

Also for the purpose of diagnosis, immunological methods are carried out. To do this, the presence of antibodies in the patient's body is determined by the indirect hemagglutination reaction. The most reliable method is to determine the genetic material of schistosomes in feces, blood, urine or other biological fluid of the patient. To do this, a polymerase chain reaction is carried out, which allows you to accurately determine the DNA of the parasite and confirm the diagnosis.

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Treatment of schistosomiasis

Treatment with schistosomes should be performed in an acute period, when the parasite in the portal vein system has not yet reached its goal and has not localized in the organs of the small pelvis or intestine. The use of specific anthelmintic drugs is most justified.

1. Ambilgar is an antiparasitic agent, the active ingredient of which is niridazole. The drug has an active effect on schistosomes, both at the stage of invasion and in organ localization. The drug is available in the form of tablets of 100 milligrams and 500 milligrams and is dosed at 25 milligrams per kilogram of body weight of the patient. Possible side effects during the administration of the drug in the form of increased excitability, drowsiness, and also possible influence on the hematopoiesis system with inhibition of all sprouts.
2. Baltricide is an anthelmintic agent, whose active ingredient is praziquantel. The drug is highly effective against trematodes, including schistosomes. The mechanism of action is the activation of the drug by the cell channels, which increase the concentration of calcium inside - this leads to the fact that there is a strong contraction of the body of the parasite without relaxation, and it dies. This drug is available in the form of tablets of 600 milligrams, the dosage of the drug is 25 milligrams per kilogram of the patient's body weight per day. Possible side effects during the administration of the drug in severe helminthic invasion - nausea, abdominal pain, itching of the skin, as well as severe intoxication manifestations.

It is also necessary to carry out symptomatic treatment. With severe symptoms of intestinal toxoplasmosis, it is necessary to prescribe antispasmodics (Baralgin, Drotaverin), probiotics (Yogurt, Enterol, Lactile), as well as antidiarrhoea. It is important to adhere to a diet to supplement energy deficiency and prevent symptoms from the intestines.

Prevention

Prevention of schistosomiasis should be carried out in areas with an epidemiological situation for this disease. It is necessary to inform people about this disease, about the ways of its transmission, as well as in the sources of active infection, to sanitize them. Patients should be treated and sanitized possible ways of transmission of infection. If there is evidence of contact with a reservoir and similar clinical manifestations, then it is necessary to conduct specific prophylaxis with the use of anthelmintic agents for therapeutic or preventive purposes.

Schistosomes are parasites that infect humans by contact with contaminated water when they get through the skin or intestines. They have a very wide path of migration through the body, which can cause many pathological symptoms. In this case schistosomes feed on erythrocytes, and when localized in the genitourinary system or intestine, then lead to a mechanical and toxic effect. The treatment of schistosomiasis is problematic, and given the serious complications, it is necessary to prevent this pathology.