Schistosomiasis is a helminthic disease caused by blood flukes-schistosomes; occurring with toxic-allergic reactions, damage to the gastrointestinal tract or genitourinary organs. The acute period is characterized by fever, papular rashes and itching of the skin; in the chronic stage, cystitis, pyelonephritis, hydronephrosis, colpitis, prostatitis, epididymitis or colitis, hepatosplenomegaly, ascites may develop. Disease is diagnosed due to the detection of helminth eggs in urine or feces samples, cystoscopy, urography. Anthelmintic agents are used to treat schistosomiasis; surgical treatment is performed according to indications.
General information
Schistosomiasis (bilgarciosis) – trematodoses caused by helminths of the genus Schistosoma and including genitourinary, intestinal and Japanese schistosomiasis. Helminthiasis is widespread in Asia, Africa, and Latin America. According to WHO statistics, 300 million people suffer from schistosomiasis; 500 thousand inhabitants of endemic countries die annually from this disease and its complications. Men are infected with schistosomiasis 5 times more often than women. The chronic course leads to disability of the able-bodied population, and in children it causes anemia, slowing down of physical and mental development. Due to the specifics of the disease, the study, in addition to infectious diseases, is engaged in urology and gastroenterology.
Causes
Blood flukes that cause schistosomiasis belong to the class Trematoda, genus Schistosoma. These are flat bisexual helminths 4-20 mm long, 0.25 mm wide. On the body of the helminth there are 2 suckers – oral and abdominal, located close to each other. Female schistosomes are longer and thinner than males. On the male’s body there is a longitudinal groove (gynecoform canal), with which he holds the female. Schistosome eggs have a diameter of 0.1 mm, oval shape and a large spike on one of the poles. Several types of schistosomes can parasitize in the human body: S.haematobium (causative agent of genitourinary form), S.mansoni (causative agent of intestinal form), S.japonicum (causative agent of Japanese form), etc.
The final host of sexually mature schistosomes and the reservoir of infection is humans and mammals. In their body, schistosomes parasitize in the small veins of the large intestine, abdominal cavity, pelvis, uterus, and bladder. Helminths feed on blood, and also partially adsorb nutrients through the cuticle. Eggs laid by schistosomes migrate to the bladder or intestines, where they ripen and from where they are excreted with urine and feces from the body. When entering freshwater reservoirs, the larval form of the helminth – miracidium comes out of the egg, the further development of which requires the presence of an intermediate host – freshwater mollusks. Having penetrated into the body of the mollusk, the miracidia are in it for 4-8 weeks; during this time they undergo a cycle of asexual reproduction, as a result of which tailed larvae of schistosomes – cercaria are formed.
Invasive larvae re-enter the water, from where they can enter the human body through intact skin or mucous membranes. Infection of a person with schistosomiasis can occur during bathing, water intake, washing clothes, watering the land, religious rituals, etc. With the help of secreted lytic enzymes and active movement, larvae are introduced into the capillaries of the skin, venules, reach the right parts of the heart and pulmonary capillaries. After 5 days from the start of migration, metacercariae reach the portal vein and its hepatic branches, and after another 3 weeks they finally settle in the duodenal, mesenteric venous plexuses, bladder vessels. After 2.5-3 months, the larvae turn into sexually mature schistosomes and begin to lay eggs. The peculiarity of parasitizing pathogens of schistosomiasis is the ability of eggs to penetrate through the vascular wall, exit into the surrounding tissues and the lumen of hollow organs (intestines and bladder) and from there to be released into the external environment.
During the migration phase of larvae, manifestations of schistosomiasis are associated with the destruction of small blood vessels, hemorrhagic reactions. The deposition of eggs in the submucosal, mucous or muscular layer of the bladder and the walls of the ureter causes a specific inflammatory process with the formation of schistosomiasis granulomas and ulcers, the development of fibrosis and wrinkling of the bladder, calcification of eggs. Prolonged presence of ulcerative defects can lead to the development of bladder cancer. Intestinal schistosomiasis is accompanied by schistosomiasis colitis with an outcome in sclerosis of the intestinal wall; schistosomiasis appendicitis may develop.
Schistosomiasis symptoms
During genitourinary schistosomiasis, acute, chronic stages and the stage of outcome are distinguished. The acute period of the disease coincides with the phase of larval migration through the bloodstream. At an early stage of schistosomiasis, patients are concerned about allergic reactions such as urticaria, local swelling of the skin. Cough, hemoptysis, hepatosplenomegaly, lymphadenopathy may occur. General toxic symptoms include fever, chills, sweating, muscle and joint pain, and headache.
A few months after the invasion, schistosomiasis turns into a chronic form, which can have a mild, moderate and severe course. With a mild form of schistosomiasis, well-being is not disturbed, performance is maintained, dysuric disorders are insignificant. Schistosomiasis of moderate severity occurs with pronounced dysuria, terminal (sometimes total) hematuria, enlargement of the liver and spleen, and the development of anemia. Severe schistosomiasis is accompanied by frequent exacerbations of cystitis, pyelonephritis, the formation of stones in the ureters and bladder. Colpitis, vaginal bleeding in women, epididymitis and prostatitis in men may develop. Late complications of schistosomiasis are infertility, ureteral strictures, hydronephrosis, cirrhosis of the liver, CRF. Severe forms of invasion lead to the loss of patients’ ability to work and can end fatally.
The early phase of intestinal schistosomiasis proceeds with the same clinical signs as its genitourinary form (fever, malaise, arthralgia and myalgia, etc.). Characterized by poor appetite, abdominal pain of aching or cramping nature, tenesmus, diarrhea with an admixture of blood, alternating with constipation. In the late stage, liver enlargement, portal hypertension, ascites, gastrointestinal bleeding, pulmonary hypertension and pulmonary heart develop. The clinic of Japanese schistosomiasis resembles the intestinal form (allergy, colitis, hepatitis, cirrhosis of the liver), but the symptoms are more pronounced.
Diagnostics
The main diagnostic data are obtained by collecting an epidemiological history, analyzing clinical manifestations, conducting laboratory and instrumental studies. In addition to infectious diseases, urologists and gastroenterologists may be involved in the diagnosis of schistosomiasis. The alertness of specialists should be caused by the fact that the patient is in an endemic focus, a combination of toxic and allergic symptoms with dysuria, hematuria, colitis.
A crucial role in the diagnosis of schistosomiasis belongs to the detection of schistosome eggs in the study of urine and feces. Standard methods for the detection of genitourinary schistosomiasis are methods of settling, centrifugation or filtration of urine; intestinal – methods of Kato, Ritchie, precipitation. In the general analysis of urine, hematuria, proteinuria, leukocyturia are detected. It is informative to conduct a cystoscopy, during which it is possible to detect schistosomiasis granulomas and ulcers, polypoid growths, clusters of schistosome eggs, as well as to conduct a biopsy of a pathologically altered area of the bladder. Overview and excretory urography allow you to see foci of calcification in the wall of the bladder or ureter, kidney stones, ureter strictures, hydronephrotic transformation of the kidney, etc. With intestinal schistosomiasis, laparoscopy and liver biopsy can additionally be performed.
For the preliminary diagnosis of schistosomiasis, immunological tests are used – RSC, RNGA, ELISA. During mass surveys of the population in endemic areas, intradermal allergy tests with schistosomiasis antigen are carried out. Genitourinary schistosomiasis requires differentiation with urolithiasis, tuberculosis of the bladder; intestinal schistosomiasis – with amoebiasis, typhoid fever, dysentery, colon cancer.
Schistosomiasis treatment
Drug therapy of schistosomiasis is effective in the early stages, in the absence of complications; in the latter cases, it is often necessary to resort to surgical treatment. In all forms of schistosomiasis, anthelmintic agents can be used: praziquantel, tinidazole, metrifonate. The success of the therapy is assessed on the basis of repeated helminthological studies and serological reactions. Surgical tactics are usually required for complications of genitourinary schistosomiasis and may include operations on the ureters (with the development of stricture), removal of stones from the bladder and kidneys.
With the timely appointment of specific therapy, the prognosis of uncomplicated schistosomiasis is favorable. Long-term chronic course of helminthiasis can lead to disability and death of the patient from the developed complications. The complex of measures for the prevention of schistosomiasis includes the treatment of reservoirs in order to destroy gastropods, active sanitary and educational work, timely identification and treatment of patients. The population of endemic foci is recommended to boil or filter water for drinking and household needs, use protective clothing (rubber gloves and boots) when in contact with water.
