Schistosoma haematobium was found in Africa and the middle east. It is a species of the digenetic trematode that belongs to the group of blood flukes responsible for causing a type of schistosomiasis known as Urinary Schistosomiasis.
It is the major agent of schistosomiasis and the most prevalent parasitic infection in humans.Schistosoma haematobium is the only flukes that affects the urinary tract and is capable of causing bladder cancer. This disease is caused by the eggs of Schistosoma haematobium.The Inflammation of the genitals due to the infection of Schistosoma haematobium may greatly contribute to the propagation of HIV.
Schistosoma haematobium adult worms are always found around the venous plexuses of the minor pelvis of the kidney where they releases eggs that travels to the walls of the bladder causing haematuria (Blood in urine) and cancer of the bladder. It has an incubation period of 10 to 12 weeks or longer with a high morbidity rate of 50 to 70%.Schistosoma haematobium has the highest occurrence among the different species of Schistosoma and has been known for over a period of 3000 years in Africa (Egypt) where it has the world’s highest incidence rate.
Morphology of Schistosoma Haematobium
The Egg (Ova)
The eggs are ovoid in shape with a distinctive terminal spine from other schistosoma species and is an important laboratory diagnostic feature.These eggs has a length of about 83-187 µm by 60-70 micrometers width is mostly recovered in urine with a 3% chance of recovering it stool when viewed under a microscope. The eggs lie in a chainlike rows within small veins at the site of their deposition.
Schistosoma haematobium cercaria has a characteristic bifurcated tail which is classically called furcae meaning fork tail in latin and greek.The body measures 0.24 mm in length and 0.1 mm in width with a pear-shaped .The tegument is fully covered with spine and a conspicuous oral sucker at the tip of the pear-shaped body.
Schistosoma haematobium miracidium has a length of about 136 μm long and 55 μm wide. The body is generally covered by anucleate epidermal plates separated by epidermal ridges. This epidermal cells give off numerous hair-like cilia structures on the body surface. The epidermal plates are absent only at the extreme anterior called apical papilla, or terebratorium made up of numerous sensory organelles. The internal body is almost fully filled with vesicles and glycogen particles
Adult Schistosoma haematobium
- The adult is monoecious that is, made up of the male and female sex organs in one body, but with distinct male and female body.
- The Male and female are paired as an individual which is a condition called in copula.
- The male forms the flatworm part, measuring 10–18 mm in length and 1 mm in width
- It also bears oral and ventral suckers towards its anterior end
- It has a leaf-like flat body curled up from both sides to form a gynaecophoric canal which is a sort of channel or groove in which the female is wrapped up giving the general appearance of a cylindrical roundworm body.
- Only the extreme anterior and posterior ends of the female are exposed.In contrast to the male,female exhibits every feature of a roundworm.
- The female is cylindrical and elongated, measuring about 20 mm in length and 0.25 mm in width. Its pathogenic armament
- the adult male worm are thicker than the female but the longer than the male
Schistosoma haematobium Transmission
- The mode of transmission of Schistosoma haematobium occurs through direct contact with water containing free swimming larvae of schistosoma called cercariae which happens to be the infective stage the parasite.
- upon direct penetration through skin of these bifid-tailed embryos (cercariae) ,They shed their tails and are taken up via the bloods vessels where the adult worms lives and where the females releases their eggs.
- Most people also get it from drinking contaminated water,swimming in pools,rivers ,beach and ocean.
- Some of the eggs are passed out from the body through faeces or urine to fresh water sources in order to continue the parasite’s life cycle.
Schistosoma Haematobium life cycle
- It starts by the release of schistosoma eggs by adult worms in the urinary tract and excretion along with the urine in fresh water bodies.
- These released eggs hatches within 15 minutes into the larvae called miracidia.
- Each miracidium is either male or female and are covered with hair-like cilia with which actively swims searching for snails.
- These miracidia has to infect or penetrates a snail within 24–28 hours or they will die from running out of energy, that is glycogen reserves
- The following snails species belonging to the genus Bulinus, including B. globosus, B. forskalii, B. nasutus, B. nyassanus, and B. truncatus can harbour the miracidia of schistosoma
- These miracidia are able to simply pierce through the soft skin of the snail and migrate to the liver
- The Miracidia transforms into sporocysts and undergo active cell division after two weeks
- The mother sporocyst produces many daughter sporocysts. Each daughter sporocyst forms new larvae called cercariae which is the infective stage of schistosoma
- These cercariae can now penetrate the human skin to causing Schistosomiasis. They also lose their fork tail while penetrating the human skin such that only the head enters the blood vessels and theyr are called schisotomulae.
- After shedding their tails,They enter the systemic system to reach the heart and then the liver where they live on erythrocytes, and along the way many are killed by the immune cells. Survivors enter the liver within 24 hours. From the liver they enter the portal vein to reach different parts of the body and develop into male and female worms.
- Schistosoma haematobium has an affinity for the Bladder venous plexus, which it reaches through the portosystemic anastomotic channels
- When the worms reach the bladder, the female worm eventually enters a submucous venule which is so small that she completely blocks it and starts laying ova in a chain; each ovum is provided with a terminal spine that penetrates the vessel wall
- The life cycle of schistosoma haematobium is completed when the eggs become released into stool or urine as illustrated below
Pathogenesis of Schistosoma Haematobium
Majority of the signs and symptoms of Schistosoma haematobium infection are caused by passage of the eggs through the walls of the urinary tract causing granulomatous reaction as a result of deposition of Schistosoma haematobiumeggs in tissues especially the bladder and leading to sandy patches and microgranulomas; Schistosoma haematobium can cause obstruction of the ureteric orifices resulting in obstructive uropathy.
In some rare cases, the parasite eggs may be carried to other parts of the body apart from the bladder.This is known as Metastatic schistosomiasis.
- When the eggs are in the central nervous system , it causes Cerebral Schistosomiasis by compressing the spinal cord and causing acute paraplegia.
- When the eggs are in the lungs, they cause Pulmonary schistosomiasis by triggering fibrous reaction leading to pulmonary fibrosis and pulmonary hypertension.
- Other organs can also be affected such as endocrine organs and gonads.
Schistosoma Haematobium Symptoms and Signs
These signs and symptoms mostly result from the antigenic substances release by the egg that trigger immune response. There are two symptoms types thus Early and Late symptoms
Katayama Syndrome (Early symptoms of Schistosoma haematobium)
- Eosinophilia (Increase eosinophil level common with parasitic infections)
- Hives also known as Urticaria a is a kind of skin rash with red, raised, itchy bumps.That may also burn or sting.
- Pruritus or Itching at the site of penetration of cercariae for about 1 to 2 days followed by Katayama Fever 3 to 5 weeks after itching
- Muscle aches
- Abdominal pain
- Breathing difficulties
Late symptoms of schistosoma haematobium (Chronic stage)
Many people do not show symptoms at the early stage, but may develop symptoms as the disease progresses in the urinary system.
- blood in the urine (Haematuria)
- painful urination (dysuria)
- Groin pain
- higher risk of bladder cancer
- Children may have stunted growth and a reduced capability to learn
- Painless terminal hematuria (especially in children) while other complications occur in adults. The hematuria is intermittent and usually occurs after strenuous exercise and is found in about 50% of patients
- Frequency of micturition (Urinating frequently)
- Over time, there’s a chance of developing anemia and some rare cases where the parasite may affect the central nervous system (Cerebral Schistosomiasis)
Laboratory Diagnosis Schistosoma haematobium
- The best diagnosis is by identifying the egg in urine wet mount using light microscope
- Also rectal snip for the identification of Schistosoma haematobium ova
- Urea, Electrolyte and Creatinine levels to check for renal status
- Cystoscopy may show typical urinary bladder lesions such as bladder wall fibrosis and calcifications
- Bladder biopsy and histology demonstrates ova in biopsy sample
- Abdominal Ultrasound scan may show hydroureter and hydronephrosis
- Intravenous Urogram may reveal contracted bladder
- Quantitative urine filtration is the most reliable method
- Concentration techniques such as Kato techniques,hatching methods and formol ether in diagnosis of schistosomiasis.
- Alternatively diagnosis can be made by complement fixation tests
- commercial blood tests included ELISA and an Indirect immunofluorescence test, but these have low sensitivity ranging from 21% to 71%
Prevention of Schistosoma haematobium
- By regular drug therapy of specific population groups
- Uses of molluscicide to eliminate snails populations in freshwater bodies
- The provision of safe and adequate clean water
- Environmental hygiene to avoid improper disposal of human feces and treatment of sewage or gabbages
- Avoidance of skin contact with natural or artificial bodies of water (freshwater)
- Adding Hydrochloric acid in well waters which contains chlorine that kills schistosoma larva
Treatment of Schistosoma Haematobium
There is currently no vaccine available for schistosomiasis, but treatment can help reduce the impact of infection
- The best drug of choice for the treatment of Schistosoma haematobium is Praziquantel a quinolone derivative..
- Metrifonate is also an alternative drug that is effective against these parasite
Some complication of Schistosoma haematobium
- Hematuria in Children mostly observed at the end of urination and it’s painless
- When chronic,gives rise to bladder cancer
- Calcifications of the urinary Bladder wall
- Fibrosis of the bladder wall due to secondary infection
- Pyelonephritis ( inflammation of the kidney)
- Hydronephrosis that is the swelling of a kidney due to a build-up of urine cause by a blocage
- Granulomas (Bilharzial masses) – caused by the aggregation of nodules
- Urethral strictures( narrowing of the urethra.This is caused by injury, instrumentation, infection and certain non-infectious forms of urethritis)
- Bilharzial pseudo tubercles the earliest specific sign of schistosoma haematobium to appear that can be detected through cystoscopy.
- Bilharzial nodules these develop by the fusion of tubercles
- Papillomas these are more pedunculated
- Sandy patches that occur as a result of calcified dead ova with degeneration of the overlying epithelium
- Ulceration as the result of sloughing of the mucous membrane of the bladder containing dead ova
- What are other species of Schistosomiasis?
- What is the Diagnostic stage of Schistosoma’s species
- How many host does schistosoma has?
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