Japanese Schistosomiasis

What is Japanese Schistosomiasis?

Japanese schistosomiasis (schistosomosis japonica, Katayama disease) is a chronic disease that occurs with a primary lesion of the gastrointestinal tract.

Japanese schistosomiasis is recorded in southern China, Taiwan, the Philippines, southern Japan, and Sulawesi.

Causes of Japanese Schistosomiasis

The causative agent of Japanese schistosomiasis is Schistosoma japonicum Katsurada. The male is 9.5-17.8 mm long, 0.55-0.97 mm wide, the female is 15-20 mm long, 0.31-0.46 mm wide. Oval eggs 0.074-0.106 x 0.06-0.08 mm with a spike located on its side.

At the stage of puberty, helminth parasitizes in the portal and mesenteric veins of humans, cattle and small cattle, pigs, dogs, cats, rats, mice, monkeys, etc. It is very likely that this type of schistosome can parasitize in the body of all mammals. A feature of Schistosoma japonicum is that pairs of helminths constantly remain in one place and produce up to 3000-5000 eggs. Parasites begin to lay their eggs about 4 weeks after infection.

Japanese schistosomiasis is a natural focal disease. The source is not only sick, but also domestic and wild animals. Intermediate hosts – S. japonicum – mollusks of the genus Oncomelania. The invasion by cercariae occurs in the water or when barefoot walks along the moist coastal grass of water bodies, since cercariae can creep up the stems of plants.

Pathogenesis during Schistosomiasis Japanese

much in common with Manson’s intestinal schistosomiasis. However, the development of pathological changes both in the intestinal wall and in the liver occurs earlier and more intensively, the sites of fibrosis and calcification are large. The more severe course of Japanese schistosomiasis is due to the fact that each individual S. japonicum produces 10 times more eggs than other types of schistosomes, and their large clusters form in the tissues. In the late stage, with the development of tubular-inductive fibrosis of the liver, cell infiltration assumes a diffuse character. Destruction of the portal vein branches causes severe portal hypertension with splenomegaly and the development of collateral circulation. The central nervous system is often affected in connection with the introduction of helminth eggs into the brain.

Symptoms of Japanese Schistosomiasis

The incubation period lasts 10-12 weeks. The clinical manifestations of schistosomiasis are different. The disease can be asymptomatic, easy, but in some cases severe and fulminant forms are described, associated with severe intoxication and allergization of the body by parasite vital products. There are three stages of the disease – initial, acute and chronic.

The acute phase of the disease is accompanied by fever, rash, swelling, pain in the intestines, diarrhea, seizures, hypereosinophilia (blood eosinophils level up to 60% or more). Known fulminant form with a sudden onset, severe allergic symptoms, extremely severe course, the development of meningoencephalitis and death. In the chronic stage of the disease, disorders of the gastrointestinal tract predominate, accompanied by abdominal pain, diarrhea with mucus and blood, an enlarged liver and spleen.

3-5 years after infection, cirrhosis of the liver often develops with splenomegaly, ascites, and expansion of the superficial veins and veins of the esophagus. The death of such patients occurs due to bleeding from varicose veins of the lower esophagus, less often – from liver failure. Schistosomal invasion has a depressing effect on the pituitary gland and the function of the sexual glands, as a result of which growth and puberty are slowed down in those invaded in the foci.

A serious complication of the chronic stage of Japanese schistosomiasis is damage to the central nervous system, due to the introduction of eggs into the brain substance. In the acute phase of the disease, diffuse brain lesions of an allergic nature can develop, in the chronic stage, focal lesions simulating a brain tumor are more often observed. Signs of involvement in the central nervous system process are epileptic seizures, paresis, paralysis of the extremities, blindness. The prognosis of Japanese schistosomiasis is much harder than with other schistosomiasis, as cirrhosis of the liver and lesions of the central nervous system more often develop.

Diagnosis of Schistosomiasis Japanese

The diagnosis is based on the detection of eggs in the feces. There are many eggs in feces only with intensive invasion. About 80% of eggs laid by helminths are delayed and die in the host tissues. Therefore, smears on glass slides should be made large and viewed under a binocular microscope, or “thick” smears should be prepared according to the Kato method, as well as the application of deposition methods and repeated studies. Schistosome eggs are larger in the first portion of feces, since they are secreted from the mucous membrane of the colon mainly in its lower parts. With negative results of coproscopy, rectal mucus is examined, which can be taken with a finger in a rubber glove immediately after the act of defecation.

A method for detecting schistosome larvae in the feces is also used, based on their phototropism. To do this, use a flask with a capacity of 500 ml with a glass tube soldered to the side at the bottom upward. 20 g of feces are placed in a flask and washed with a stream of tap water. 250 ml of water is left in the flask, covered with a cap of opaque black paper or placed in a dark box so that the side tube remains illuminated. After 2 hours at a temperature of 25 ° C, miracidia hatch from the eggs of schistosomes, which, due to positive phototropism, accumulate in the side tube. Here they can be observed with a magnifier or even with the naked eye.

To identify inactive schistosomiasis, sometimes during rectoscopy, a biopsy of a piece of pathologically altered tissue from the intestinal mucosa is performed at a distance of about 10 cm from the anus. Pieces of biopsy tissue are crushed between two glass slides in a few drops of a 50% glycerol solution and microscopic. In positive cases, characteristic schistosome eggs are found in the mucous membrane.

Also, during sigmoidoscopy, hyperemia of the mucous membrane of the distal segment of the colon, erosive-ulcerative changes, schistosomal tubercles, intestinal polyposis (in the later stages of the development of the disease) are revealed. In recent years, immunological methods for the recognition of schistosomiasis have become widely used – an intradermal allergy test with an antigen prepared from miracidia, the liver of infected mollusks, cercariae and mature schistosomes, complement fixation reactions, precipitation and flocculation.

Japanese Schistosomiasis Treatment

In the past, the main agents for the treatment of schistosomiasis were trivalent antimony preparations (emetic stone, fuadin, anti-malin, astiban). All preparations of trivalent antimony, although effective, are highly toxic and require a long course of treatment. In this regard, at present, these funds for the treatment of schistosomiasis are practically not used. Praziquantel (Praziquantel, Biltricid), which is a derivative of isoquinoline-piperazine, is highly effective in all schistosomiasis. Assign it inside at a dose of 20-60 mg / kg body weight in 1-3 doses for 1 day. The drug is effective in 90-100% of patients.

Metrifonate (Bilaroit) – an organophosphorus anticholin-esterase compound, is a reserve drug for S. haematobium invasion. It is administered once enteral at a dose of 7.5-10 mg / kg body weight. Repeated treatment is sometimes necessary after 2-4 weeks. Side effects (nausea, vomiting, abdominal pain, diarrhea, weakness) are rare. Treatment is effective in 40-80% of patients.

Oxamniquine is a derivative of 2-aminomethyltetrahydroquinoline, a reserve preparation for invasion of S. mansoni. It is effective for enteral administration at the rate of 15 mg / kg 2 times a day for 2 consecutive days. In the coming days after treatment, the content of serum aminotransferases (hepatotoxic effect) increases. The drug is effective in 50-90% of patients.

Niridazol (Ambilhar) is close in structure to furazolidone and metronidazole, is available in tablets of 0.1-0.5 g. It is prescribed for oral administration during invasion of 5. haemalobium for adults in a daily dose of 25 mg / kg of patient weight for 5-7 days . The daily dose of the drug is divided into 2 doses: morning and evening after eating. In case of side effects (hallucinations, convulsions), the drug is canceled. There are ECG changes in the form of a flattening of the T wave and a decrease in the S-T line, a rash on the skin of an allergic origin, a feeling of fatigue, heaviness in the muscles. Urine acquires a dark brown color, which is not a reason for discontinuing the drug. After a course of treatment, the urine acquires the usual color. Ambilgar is considered the most effective drug in the treatment of genitourinary and intestinal schistosomiasis. The effectiveness of the drug is observed in 40-80% of patients.

Hycanthone (Etrenol) – a derivative of miracil. It is administered once intramuscularly at a dose of 2-3 mg / kg. Side effects (nausea, vomiting, abdominal pain, occasionally liver damage) are usually mild. The effectiveness of the drug was observed in 40-80% of patients.

The effectiveness of the therapy is assessed on the basis of a long (over several months) and thorough clinical and helminthological examination, as relapses are possible. Serological reactions are used to monitor the effectiveness of specific treatment for schistosomiasis. They become negative 3 months after the disappearance of helminthic invasion. Specific therapy should be carried out in combination with pathogenetic methods of treatment. In secondary infections, antibiotics are used, in case of severe cirrhosis, splenic vein thrombosis, polyposis, strictures, along with vitamin therapy and diet therapy, surgical treatment is carried out.

The prognosis is favorable for all forms of schistosomiasis due to the chronic course of the disease. However, in severe and very severe forms of the course of infestations, cirrhosis of the liver develops, which leads to death. Light and moderate forms of invasion can be treated with modern methods of therapy.

Japanese Schistosomiasis Prevention

The fight against schistosomiasis should be based on breaking the life cycle of schistosomes at any stage. The fight against the disease and its prevention should be carried out comprehensively, and it should include:

  1. treatment of patients with schistosomiasis;
  2. accounting for all patients with schistosomiasis;
  3. periodic verification of long-term results of treatment by examining feces for schistosome eggs;
  4. active detection of latent or initial stages of the disease using laboratory methods for the study of urine and feces;
  5. medical examination of the personnel of the ships. Activities in the outbreak:
    1. Extermination of mollusks:
    – the use of molluscicides;
    – proper design and operation of irrigation systems;
    – periodic cleaning, drying and removal of vegetation from irrigation ditches and water basins.
    2. Conducting sanitary-technical measures:
    – organization of centralized water supply and provision of personnel with benign water;
    – the prohibition to use water from sources that could have been infected for drinking, bathing and household needs;
    – constant and persistent sanitary and educational work.