Genitourinary schistosomiasis: causes, symptoms, diagnosis, treatment

Urogenital schistosomiasis is a chronic tropical trematodosis that occurs with damage to the genitourinary organs.

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Epidemiology of urogenital schistosomiasis

Schistosomes live in small venous blood vessels of the genitourinary system, in the venous plexuses of the small pelvis, urinary bladder, uterus, and are found in the portal vein system and branches of the mesenteric vein of mammals. They feed on blood, partially adsorbing nutrients through the cuticle.

The laid eggs migrate to the urinary bladder, mature for 5-12 days in the host tissues and are excreted from the body with urine. The final maturation of miracidium occurs in fresh water at a temperature of 10-30 °C. In water, miracidia emerge from the eggs, which penetrate into freshwater mollusks of the genus Bulinus, where they develop into cercariae over 3-6 weeks according to the scheme: miracidia - mother sporocyst - daughter sporocysts - cercariae. Cercariae, having emerged from the mollusc, are capable of invading the final host within 3 days. Cercariae penetrate through the skin or mucous membrane of the oropharyngeal cavity into the body of the final host, where they turn into young schistosomula, migrate to the venous vessels of the genitourinary organs, develop and reach sexual maturity. Mating occurs 4-5 weeks after penetration into the host, then the females lay eggs in small venous vessels.

With the help of a sharp spine and cytolysins secreted by the larvae in the eggs, some of the eggs penetrate the walls of blood vessels and the tissues of the mucous membrane into the lumen of the bladder, from where they are excreted with urine. Many eggs are retained in the wall of the bladder and surrounding tissues, causing inflammation. One pair of schistosomes produces 2000-3000 eggs per day. The lifespan of adult schistosomes is on average 5-10 years (although there are cases of them parasitizing humans for 15-29 years).

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What causes urogenital schistosomiasis?

Urogenital schistosomiasis is caused by Schistosoma haematobium. The size of the male is 10-15 mm, the female - 20 mm (Fig. 4.1). The body of the male is thickened, flat, while that of the female is filiform and longer. The suckers are poorly developed. In the male, the cuticle behind the abdominal sucker with its lateral outgrowths forms a longitudinal slit-like gynecophoric canal in which the female is placed.

The cuticle of the male is completely covered with spines, while females have them only at the anterior end. There is no pharynx. The esophagus of males and females first bifurcates into two branches of the intestine, which then merge again. There are 4-5 testicles, located in the anterior or posterior part of the body. The ovary is located at the confluence of the intestinal branches, with the yolk sacs located behind it. The genital opening is located behind the abdominal sucker. The eggs are oval, without a lid, with a terminal spine characteristic of the species, measuring 120-160 x 40-60 µm.

The pathogens are widespread in tropical and subtropical countries between 38° N and 33° S, where, according to WHO, up to 200 million new cases of infection occur annually. The incidence of schistosomes is highest in people aged 10 to 30 years. Agricultural workers and irrigation system workers are at increased risk of infection. The disease is widespread in most countries of Africa and the Middle East (Iraq, Syria, Saudi Arabia, Israel, Yemen, Iran, India), as well as on the islands of Cyprus, Mauritius, Madagascar and Australia.

In terms of its socio-economic significance among parasitic diseases, schistosomiasis ranks second in the world after malaria.

Symptoms of urogenital schistosomiasis

The acute period of urogenital schistosomiasis coincides with the penetration of cercariae into the host organism and the migration of schistosomulae through the blood vessels. During this period, at the stage of cercariae penetration, symptoms of urogenital schistosomiasis such as dilation of skin vessels, redness, fever, itching and swelling of the skin are observed. These phenomena disappear in 3-4 days. After the primary reaction and a period of relative well-being, the duration of which is 3-12 weeks, the patient develops headaches, weakness, aches in the back and limbs, multiple itchy rashes such as urticaria, the number of eosinophils in the blood increases to 50% or more. The liver and spleen often enlarge.

At the end of the acute and beginning of the chronic periods, hematuria occurs, which is often terminal, i.e. blood in the urine appears at the end of urination. Patients are bothered by general malaise, pain in the bladder and perineum; body temperature rises to 37 °C and above, the liver and spleen increase in size even more. All these clinical symptoms of urogenital schistosomiasis are associated with the human body's reaction to the introduction of schistosome eggs into the tissues of the bladder, genitals and liver.

The passage of eggs through the wall of the bladder causes hyperemia of the mucous membrane and pinpoint hemorrhages. Granulomas form around the dead eggs in the thickness of the bladder wall, and tubercles and polypous growths form on their surface. Due to mechanical damage to the mucous membrane by eggs passing through the bladder wall, a secondary infection often joins in and cystitis develops, which subsequently leads to severe destruction of the bladder tissue and ulceration of the mucous membrane. The inflammatory process can spread up the ureters to the kidneys.

The chronic period of the disease begins several months after the invasion and can last for several years. The defeat of the ureters is accompanied by a narrowing of their distal parts and mouth, which leads to stagnation of urine, the formation of stones and creates conditions for the development of pyelonephritis and hydronephrosis. The late stage of the disease is characterized by the development of fibrosis of the bladder tissue and its calcification, which complicates the passage of eggs and contributes to the intensification of granulomatous processes. In these cases, the eggs are calcified. Their clusters form so-called sand spots visible during cystoscopy. As a result, the shape of the bladder changes, urine is retained, and intravesical pressure increases. The course of the disease can be mild, moderate and severe. In severe cases, urogenital schistosomiasis leads to disability and premature death.

In men, the disease may be accompanied by fibrosis of the seminiferous tubules, orchitis, prostatitis, and in women - polyposis, ulceration of the vaginal mucosa and cervix. Proctitis and bladder fistulas may develop. Sometimes pseudoelephantiasis of the genitals, colitis and hepatitis develop. Lung damage leads to hypertension of the pulmonary circulation. The development of organ fibrosis, epithelial metaplasia and immunosuppression contribute to carcinogenesis. Tumors of the genitourinary system are more common in schistosomiasis foci than in other areas.

Diagnosis of urogenital schistosomiasis

In endemic foci, a preliminary diagnosis is made based on the clinical symptoms of urogenital schistosomiasis. Patients complain of weakness, malaise, urticaria, diuretic disorders, hematuria, and the appearance of drops of blood at the end of urination.

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Laboratory diagnostics of urogenital schistosomiasis

An accurate diagnosis of urogenital schistosomiasis is established by detecting schistosome eggs in the urine, which can only be detected 30-45 days after infection. Urine is collected during the hours of maximum egg excretion (between 10 and 14 hours). Concentration methods are used for ovoscopy: settling, centrifugation or filtration.

Instrumental diagnostics of urogenital schistosomiasis is very informative. Cystoscopy reveals thinning of blood vessels, pale mucous membrane, deformation and hyperemia of the ureteral orifices, accumulations of dead and calcified schistosome eggs, and polypous growths.

X-ray examination and serological methods (for example, ELISA) are also additionally used.

Treatment of urogenital schistosomiasis

Treatment of urogenital schistosomiasis of patients is carried out in a hospital. The drug of choice is praziquantel or azinox in a daily dose of 40 mg / kg in two doses during the day. The effectiveness of the drug is 80-95%. Significant importance in the treatment of schistosomiasis is given to the methods of symptomatic and pathogenetic therapy to improve the functions of the affected organs and systems. In case of secondary infection, antibiotics are used. In case of severe cirrhosis, thrombosis of the splenic veins, polyposis, strictures, surgical treatment is performed.

Prevention of urogenital schistosomiasis

Urogenital schistosomiasis can be prevented by following a set of measures aimed at stopping the transmission of the infection and preventing infection in humans:

• timely identification and treatment of patients;
• preventing the introduction of schistosome eggs into bodies of water inhabited by mollusks;
• destruction of mollusks using molluscicides (fresco, sodium pentachlorophenolate, copper sulfate, endod, etc.);
• the spread of competitors of mollusks and predators in water bodies, which destroy the eggs of mollusks and the mollusks themselves;
• use of irrigation systems that reduce the proliferation of mollusks;
• cleaning and drying of canals and reservoirs;
• wearing protective clothing (gloves, rubber boots, etc.) when in contact with water;
• lubrication of the skin with a protective ointment (40% dimethyl phthalate or dibutyl phthalate) when swimming and working in water;
• boiling or filtering water for drinking and household needs;
• active health education work;
• centralized water supply to the population.

Personal preventive measures are of particular importance for tourists and travellers in endemic areas. These measures include careful selection of bathing areas, avoidance of overgrown freshwater bodies and places where mollusks accumulate.