Blood fluke

Blood fluke or blood Schistosoma (Schistosoma haematobium) refers to parasites such as flatworms (Phylum Plathelminthes), a class of flukes or trematodes (Trematoda Digenea), the Strigeidida group, the family Schistosomatidae.

S. Haematobium infection is still a major public health problem in most countries in Africa and the Middle East, second only to malaria among parasitic diseases.

[1], [2], [3], [4],

Epidemiology

According to WHO statistics, 180 million people worldwide live in endemic areas and 90 million are infected with this parasite. It is estimated that almost 150,000 people die each year due to complications of urogenital schistosomiasis; the total death rate is 2 per 1000 infected patients per year.

[5], [6], [7], [8], [9], [10],

Causes of the blood fluke

It should be noted that the blood fluke is a two-sexed worm, co-existing in a male-female pair. Accordingly, their structure is somewhat different. The length of the wider tubular body of the male does not exceed 10-15 mm, while the narrower female body can be 2 cm in length. Each male on the ventral part has a unique gynecophoral canal in which the female is constantly present.

On the anterior and abdominal parts of the body there are suckers, the female has an ovary behind the intestinal canal with an oviduct leading to the genital opening. The size of the oval eggs is about 0.15 mm long, on one side the eggs have a pointed shape with a spinule. Inside the eggs there are larvae - miracidia.

[11], [12], [13], [14], [15], [16]

Pathogenesis

The blood fluke is contagious for humans and causes a parasitic disease of urogenital schistosomiasis, which can lead to the development of pathological tumors.

The structure and life cycle of the blood fluke

The life cycle of the blood fluke takes place in the organisms of the two hosts. The intermediate host is the freshwater gastropods (snails) of the family Planorbidae, the genus Bulinuss, which inhabit the water bodies of Africa and the Middle East. The ultimate host is a man.

The first larval stage begins when 0.2 mi of miracidia emerge from the eggs that enter the water and have excretory organs (two pairs of protonephridia), and outside the cilium, providing free movement in the water. Penetrating the body of the cochlea, miracidia asexually divides and form two generations of sporocyst larvae. The structure of sporocysts is common, in the form of a pleomorphic body (pouch) containing developing larvae. From the sporocysts within 2-3 weeks develop cercariae - the third larval stage of the blood fluke. Growing up to about 0.3 mm, cercariae leave the body of the cochlea and again find themselves in the water. This is an invasive form, as the circus has a forked tail (furcocercous), and it quickly moves in search of the final host.

Ways of human infection - the introduction of cercariae through the skin into the body (when a person comes in contact with stagnant or slowly flowing water) and penetration into the blood. Parasitologists do not rule out infection when water enters the digestive tract through the mouth.

Cercariae discard the tail and turn into a schistosomus, with a current of blood falling into the mesenteric venules of the abdominal cavity, rectal venules and venous plexus of the bladder. Here, from each schistosoma, an adult twin worm develops by successive transformation, which is attached to the vessel's abdominal sucker, and feeds blood through the oral sucker.

4-8 weeks after infection, S. Haematobium females begin to lay eggs (200-3000 per day), which move forward towards the bladder and ureters and perforate the wall, penetrate into the bladder. When urinating, the eggs come out and enter the water. And the new life cycle of the blood fluke begins. Adult worms usually live for 2-5 years, although some can live much longer.

[17], [18]

Symptoms of the blood fluke

Not all eggs penetrate into the bladder, many of them with blood are in the organs, where in the environment of the inflammatory cells form characteristic granulomas in the form of polyps. After the death of encapsulated eggs, the granulomas solidify, causing various pathologies of the internal organs.

Genitourinary schistosomiasis, which causes a blood fluke, does not develop immediately. Early symptoms of infection with this parasite appear about a day after penetration of the sclerotis: at this point on the skin appears an itching papular rash and local edema. This period lasts about 4-5 days.

Within one to two months, the symptoms of infection can be expressed by fever, increased liver, spleen and lymph nodes. During this period, the average duration of which is from one to three weeks, there is anemia, an increase in the number of eosinophilic leukocytes in the blood (eosinophilia) or a decrease in the level of platelets. However, as doctors note, signs at an early stage of the disease are not manifested in everyone, and the course of the disease is also individual.

After a few months or even years, 50-70% of infected people may experience pain during urination and dysuria; in the urine there is blood (hematuria); also develops urethral obstruction and kidney damage in the form of obstructive nephropathy.

With dysfunction of the urinary tract, which causes blood fluke, develops hydronephrosis (accumulation of urine in the kidneys); Any bacterial infection can also join, which leads to the development of cystitis - with the corresponding symptomatology. In endoscopic examination of the bladder, granulomas (clusters of S. Haematobium eggs), polyps, ulcers, areas of calcification or keratinization of the mucosa (leukoplakia) are detected on it. During the examination of women with schistosomal invasion, focal extensions of the mucous membrane of the vagina or cervix of the uterus, fistula of the urethra are found. Also can develop intestinal polyposis, pulmonary arteritis, cardiovascular problems, including heart failure and periportal fibrosis.

[19], [20], [21],

Complications and consequences

To late complications of chronic genito-urinary schistosomias, specialists also refer to bladder carcinoma, which develops due to the progressive destruction of its wall.

[22], [23], [24], [25], [26]

Diagnostics of the blood fluke

Diagnosis of blood fluke involves the collection of anamnesis (the patient must report on the visit of endemic areas) and urine analysis (in which the eggs of the parasite are identified). Eggs are quite a characteristic diagnostic sign. In some cases, a biopsy of the bladder, rectum or vaginal wall can be used.

[27], [28], [29], [30], [31], [32]

Treatment of the blood fluke

Typically, the treatment of blood flukes is carried out with the help of such drugs as:

• Biltricide (Praziquantel): a single oral dose is calculated by body weight. At 20 mg / kg three times for one day or a single dose of 40 mg per kilogram of weight.
• Metronate: is taken within three weeks - once a week for 10 mg per kilogram of body weight.
• Hikanton (Etrenol): is administered intramuscularly once, the dose is determined from the calculation of 2-3 mg per kilogram of weight.

Corrective surgery may be necessary in cases of obstruction of the urinary tract. Complications of urogenital schistosomiasis should be treated with appropriate methods and drugs.

Prevention

Prevention of infection with blood fluke and the development of urogenital schistosomiasis is an urgent problem for endemic regions, which include more than 50 countries in Africa and the Middle East.

The blood fluke parasitizes mainly among the inhabitants of rural areas of these regions, where snails also live (intermediate hosts of trematodes); many human activities also affect the distribution of parasites, especially the construction of irrigation canals and irrigation systems.

Preventive measures include improving sanitation, biological control of the snail population that carry the blood fluke, and the use of molluscicides in controlling them. An important role is played by informing the local population and tourists visiting endemic areas.

[33], [34], [35]