Слайд 1Schistosomiasis
The topic of the lecture:
Professor Kutmanova A.Z.
Слайд 2Topics
Definition
The Pathogen
Epidemiology
Etiology and Life Cycle
Pathobiology
Clinical manifestations
Diagnosis
Treatment
Слайд 3 Schistosomiasis is an acute and chronic disease caused by
parasitic worms.
People are infected during routine agricultural, domestic, occupational,
and recreational activities, which expose them to infested water.
Lack of hygiene and certain play habits of school-aged children such as swimming or fishing in infested water make them especially vulnerable to infection.
Слайд 4 Schistosomiasis control focuses on reducing disease through periodic, large-scale
population treatment with praziquantel; a more comprehensive approach including potable
water, adequate sanitation, and snail control would also reduce transmission.
Estimates show that at least 206.5 million people required preventive treatment for schistosomiasis in 2016, out of which more than 88 million people were reported to have been treated.
Слайд 5History
Schistosomiasis is known as bilharzia or bilharziosis in many countries,
after German physician Theodor Bilharz, who first described the cause
of urinary schistosomiasis in 1851.
The first doctor who described the entire disease cycle was Piraja da Silva in 1908.
It was a common cause of death for Ancient Egyptians in the Greco-Roman Period.
Слайд 6The pathogen
Schistosomiasis is one of the most important parasitic diseases
of humans and is a global public health problem in
the developing world.
Schistosomiasis is caused by blood flukes (trematode worms) of the genus Schistosoma.
Слайд 7The Pathogen
The large male (0.6 to 2.2 cm × 2
to 4 mm) has a ventral gynecophoric canal in which
the female (1.2 to 2.6 cm × 1 to 2 mm) is held during copulation.
Слайд 10EPIDEMIOLOGY
Infection sources
Mode of transmission
Susceptible population
Слайд 11Infection sources
Patients
reservoir host – animal reservoirs
cows, pigs(S. japonicum)
Rodents, monkeys, and baboons have been found infected in
nature, but the role of these animals as reservoirs does not seem to be epidemiologically important.
Слайд 12The freshwater snail intermediate hosts are Biomphalaria spp in Africa
and Biomphalaria glabrata (Australorbis) and Tropicarbis in South America and
the West Indies.
Слайд 13Transmission
People become infected when larval forms of the parasite –
released by freshwater snails – penetrate the skin during contact
with infested water.
Transmission occurs when people suffering from schistosomiasis contaminate freshwater sources with their excreta containing parasite eggs, which hatch in water.
Слайд 14Schistosoma life cycle
4 to 7 weeks
72 hours
6 weeks
Слайд 17PATHOPHYSIOLOGY
Adult worms release eggs in the venules of the mesentery,
and the eggs enter the liver through the portal vein,
where they become lodged in the terminal branches of the portal venules.
The lodged eggs cause a granulomatous inflammation, and the lesions are healed by periportal fibrosis.
S. japonicum is more virulent than S. mansoni because its infection produces ten times more eggs.
Слайд 18Because the habitat of S. mansoni, S. japonicum, S. mekongi,
and S. intercalatum worms is the mesenteric blood vessels, the
intestines are involved primarily, and egg embolism results in secondary involvement of the liver.
In the liver, the granulomas result in perisinusoidal obstruction of portal blood flow, portal hypertension, splenomegaly, esophageal varices, and portosystemic collateral circulation.
Liver cell perfusion is not reduced; consequently, liver function test results remain normal for a long time.
PATHOPHYSIOLOGY
Слайд 19CLINICAL MANIFESTATIONS
Clinical manifestations of schistosomiasis are divided into
-schistosome dermatitis
-acute schistosomiasis
-chronic schistosomiasis
Слайд 20CLINICAL MANIFESTATIONS
A pruritic papular rash occurs within 24 hours after
the penetration of cercariae and reaches maximal intensity in 2
to 3 days.
Слайд 21CLINICAL MANIFESTATIONS
( Acute schistosomiasis )
Acute schistosomiasis occurs usually 20 to
50 days after primary exposure.
The clinical syndrome (i.e., fever,
chills, liver and spleen enlargement, and marked eosinophilia) originally described for S. japonicum infection, and still common for this species, is increasingly being diagnosed in Brazil in individuals with S. mansoni infection.
Слайд 22CLINICAL MANIFESTATIONS
(Acute schistosomiasis )
Malaise, diarrhea, weight loss, cough, dyspnea,
chest pain, restrictive respiratory insufficiency and pericarditis are important findings
in this phase.
Слайд 23CLINICAL MANIFESTATIONS
( Acute schistosomiasis )
Acute disease is not observed
in individuals living in endemic areas of schistosomiasis because of
the downmodulation of the immune response by antigens or idiotypes transferred from mother to child.
Acute schistosomiasis is becoming a frequent and major clinical problem in nonimmune individuals from urban regions who are exposed for the first time to a heavy infection in an endemic area.
Слайд 24CLINICAL MANIFESTATIONS
(chronic schistosomiasis)
Abdominal pain, irregular bowel movements and blood in
the stool are the main symptoms of intestinal involvement.
Слайд 25CLINICAL MANIFESTATIONS
Patients may remain asymptomatic until the manifestation of hepatic
fibrosis and portal hypertension develops.
Слайд 26CLINICAL MANIFESTATIONS
Hepatic fibrosis is caused by a granulomatous reaction to
Schistosoma eggs that have been carried to the liver.
Hematemesis
from bleeding esophageal or gastric varices may occur. In such cases, anemia and decreasing levels of serum albumin are observed.
Слайд 27CLINICAL MANIFESTATIONS
Portal hypertension: severe hepatosplenic disease with decompensated liver disease.
Jaundice, ascites, and liver failure are then observed.
Слайд 28CLINICAL MANIFESTATIONS
In hospitalized adult patients with S. japonicum infection, cerebral
schistosomiasis occurs in 1.7 to 4.3%.
It may occur as
early as 6 weeks after infection.
Слайд 29CLINICAL MANIFESTATIONS
In S. haematobium infection, the main organ system involved
is the urinary tract.
The acute granulomatous response to parasite
eggs in the early stages causes urinary tract disease, such as urethral ulceration and bladder polyposis.
Слайд 30CLINICAL MANIFESTATIONS
In chronic disease, usually in older patients, granulomas at
the lower end of the ureters obstruct urinary flow and
may cause hydroureter and hydronephrosis.
Bladder fibrosis and calcification are also seen in this phase. Up to 70% of infected individuals have hematuria, dysuria, or urinary frequency.
Слайд 31CLINICAL MANIFESTATIONS
An increased incidence of squamous cell carcinoma of
the bladder has been reported in endemic areas of S.
haematobium infection, but the mechanism of carcinogenesis is unknown.
S. haematobium eggs have occasionally been found in the lungs, with subsequent focal pulmonary arteritis and pulmonary hypertension.
Слайд 32Basis for DIAGNOSIS
History of epidemiology: infested water contanct
Clinical manifestation
Laboratory
tests
Differentiation diagnosis
Слайд 33DIAGNOSIS
Blood routine examination
Liver function test
Liver ultrasonic
CT
Antibodies detection: Several serologic tests
for detection of IgM, IgG, and IgA antibodies to Schistosoma
antigens are available.
Examination of feces-the eggs
Rectum tissue biopsy
Слайд 34Schistosomiasis is diagnosed through the detection of parasite eggs in
stool or urine specimens.
Antibodies and/or antigens detected in blood
or urine samples are also indications of infection.
DIAGNOSIS
Слайд 35For urogenital schistosomiasis, a filtration technique using nylon, paper or
polycarbonate filters is the standard diagnostic technique. Children with S. haematobium almost
always have microscopic blood in their urine which can be detected by chemical reagent strips.
The eggs of intestinal schistosomiasis can be detected in faecal specimens through a technique using methylene blue-stained cellophane soaked in glycerine or glass slides, known as the Kato-Katz technique.
DIAGNOSIS
Слайд 36TREATMENT
Three compounds are in use metrifonate, oxamniquine, and praziquantel, and
all three are included in the World Health Organization’s list
of essential drugs.
Слайд 37Praziquantel
A pyrazinoisoquinoline derivative, is the drug of choice for the treatment
of schistosomiasis for four reasons:
high efficacy against all schistosome
species and against cestodes,
lack of serious short-term and long-term side effects,
administration as a single oral dose
competitive cost is cheap.
Слайд 38TREATMENT
The standard recommended treatment consists of a single dose of praziquantel, 40 mg/kg, for S. mansoni, S. haematobium and S. intercalatum infection.
In S.japonicum infection, a total dose of 60 mg/kg is recommended, split into two or three doses in a single day.
S. mekongi may require two treatments at 60 mg/kg body weight.
Слайд 39TREATMENT
With these dosages of praziquantel, recorded cure rates are:
75 to 85% for S.haematobium,
63 to 85% for S. mansoni,
80 to 90% for S. japonicum,
89% for S.intercalatum,
60 to 80% for double infections
with S. mansoni and S. haematobium.
Слайд 40TREATMENT
The most common side effects observed with
praziquantel or oxamniquine are related to the gastrointestinal tract: abdominal pain or discomfort, nausea, vomiting, anorexia, and diarrhea.
Слайд 41TREATMENT
These symptoms can be observed in up to 50% of patients but are usually well tolerated.
Other side effects are related to the central nervous system (e.g., headache, dizziness, drowsiness) and the skin (e.g., pruritus, eruptions) or may be nonspecific (e.g., fever, fatigue).
Слайд 42TREATMENT
Although a reduction in the intensity of infection and morbidity has been documented after mass chemotherapy, provision of clean water, use of molluscicides (kill the snail), and
adequate sanitation should also be implemented to control the disease.
Слайд 43TREATMENT
The mortality rate is 0.05% for severe S. mansoni infection and 1.8% for severe S.japonicum infection.
Bleeding from esophageal varices is the most
serious complication.
Chronic infection can lead to hepatocellular
carcinoma.
Слайд 44Summary of schistosomiasis (1)
Schistosomiasis occurs mainly in rural agricultural and
periurban areas in the developing world.
Five major species of
Schistosoma affect humans.
The intermediate hosts is snail.
Eggs, causing the portal hypertension and liver fibrosis, is very important in pathobiology and diagnosis.
Слайд 45Summary of schistosomiasis(2)
Metrifonate, oxamniquine, and praziquantel are included in the
WHO’s list of essential drugs.
Praziquantel is well tolerated and effective for different clinical forms of schistosomiasis.
