Sometimes referred to as bilharzias, bilharziasis,
or snail fever,
is a parasitic disease caused by
trematode(flukes) flatworms of the genus
Schistosoma.
Belong to Phylum Platyhelminthes
History
schistosomiasis was discovered by Theodore
Bilharz, a German surgeon working in Cairo, who
first identified the etiological agent Schistosoma
hematobium in 1851
The first doctor who described the entire
disease cycle was Pirajá da Silva in 1908.
It was a common cause of death for Ancient
Egyptians in the Greco-Roman Period.
classification
Schistosoma mansoni
Schistosoma hematobium
Schistosoma japonicum
S. intercalatum
S. mekongi
***Trichobilharzia ocellata (cause swimmers
itch)
Four species routinely infect the human host, and
several others rarely do so.
Schistosoma eggs (haematobium with terminal stings mansoni with lateral stings)
Epidemiology
It is endemic to at least 76 tropical and subtropical countries.
more than 200 million people are infected
worldwide. In terms of impact this disease is
second only to malaria as the most devastating
parasitic disease. Schistosomiasis is considered
one of the Neglected Tropical Diseases (NTDs)
The disease is found in tropical countries in
Africa, the Caribbean, eastern South America,
Southeast Asia and in the Middle East.
Schistosoma mansoni is found in parts of South
America and the Caribbean, Africa, and the
Middle East;
S. haematobium in Africa and the Middle East;
and S. japonicum in the Far East.
S. mekongi and S. intercalatum are found locally
in Southeast Asia and central West Africa,
respectively
Transmission
Risk Factor- Wading and swimming in fresh
water in tropical regions
You get a schistosoma infection through contact
with contaminated water. The parasite in its
infective stages is called a cercaria. It swims
freely in open bodies of water.
cercaria
Skin vesicles on the forearm, created by the penetration of
Schistosoma
Schistosomiasis is due to immunologic
reactions to Schistosoma eggs trapped in
tissues. Antigens released from the egg
stimulate a granulomatous reaction
involving T cells, macrophages, and
eosinophils that results in clinical disease
Initially, the inflammatory reaction is
readily reversible. In the latter stages of
the disease, the pathology is associated
with collagen deposition and fibrosis,
resulting in organ damage that may be
only partially reversible.
Photomicrography of bladder in S. hematobium infection,
showing clusters of the parasite eggs with intense
eosinophilia
Host
All snail species susceptible to infection with
Schistosoma mansoni and S. haematobium
belong to the family Planorbidae in the subclass
Pulmonata.
Schistosoma mansoni infects snails in the genus
Biomphalaria, and these can also become
infected with S. mansoni-S. intercalatum
hybrids, S. rodhaini and S. eduardiense.
Schistosoma haematobium infects pulmonate
snails of the genus Bulinus.
Oncomelania for S japonicum
Tricula (Neotricula aperta) for S mekongi
Clinical Presentation
Symptoms and signs depend on the number and
location of eggs trapped in the tissues.
Eggs can end up in the skin, brain,
muscle, adrenal glands, and eyes. As the
eggs penetrate the urinary system, they
can find their way to the female genital
region and form granulomas in the uterus,
fallopian tube, and ovaries.
Central nervous system (CNS)
involvement occurs because of
embolization of eggs from the portal
mesenteric system to the brain and spinal
cord via the paravertebral venous plexus.
location
Intestinal
S. mansoni
S. japonicum
S. intercalatum
S. mekongi
Urinary
S. hematobium
S. japonicum eggs in hepatic portal tract
Acute schistosomiasis
Katayama syndrome- is a systemic, serum
sickness-like illness that develops after several
weeks in some, but not most, individuals with
new schistosomal infections.
is associated with marked peripheral
eosinophilia and circulating immune complexes
most common with S japonicum and S mansoni
infections
is most likely to occur in heavily infected
individuals after primary infection
present usually 4-8 weeks after(exposure to S
japonicum or S mansoni) contact with infested
water
Fever, lethargy, malaise, and myalgia are the
most common symptoms
Less common symptoms
 cough,
 headache, anorexia
 rash (urticarial or papular)
 Right upper quadrant pain and
bloody diarrhea may also occur
 patients may present with focal
neurological deficits.
Chronic Intestinal Schistosomiasis
disease onset is insidious- Patients with
symptomatic chronic schistosomiasis may
present months to years after primary exposure
portal hypertension with splenomegaly
oesophagial varices, hypersplenism, ascitis,
dyspepsia, flatulence, and pain are present in
the left hypochondrium
pulmonary hypertension
CNS lesions: spine - transverse myelitis cerebral
– seizures (S. japonicum) -Dizziness, nausea,
and increased intracranial pressure, Visual
scintillation from occipital mass
intestinal polyposis: intestinal granulomatosis:
contractures of colon, intusseception, melena,
Generalized lymphadenopathy
Female genital schistosomiasis- Postcoital
bleeding, Genital ulceration, Irregular
menstruation, Pelvic pain
Cardiopulmonary schistosomiasis - larval
pneumonitis with a cough, mild wheezing, and a
low-grade fever, while in schistosomal cor
pulmonale, easy fatigability, palpitations,
dyspnea on exertion, and hemoptysis
Splenomegaly due to
bilharziosis:
a drawing of the contour
before ablation and the spleen
after excision
Tortuous Varicosities in Chronic Schistosomiasis
Cercarial dermatitis of
humans ("swimmer's itch",
"Badedermatitis",
"Weiherhippel")
Trichobilharzia ocellata
Schistosoma near urethra
Presentation
hematuria (terminal)
urinary frequency
pyuria
pyelonephritis
obstructive uropathy
cancer of bladder (squamous cell)
distant metastases (spinal column)
(pulmonary hypertension)
symptoms mimic any acute viral, bacterial, or
malarial illness.
Obtaining a careful travel history, including
drinking water sources and recreational
activities, is important. Symptoms are likely
secondary to immune complex formation
following egg deposition in tissues; the illness
resembles serum sickness.
Diagnosis: intestinal schistosomiasis
1. History of freshwater exposure
2. Stool for O&P (egg counts and viability)
3. Serology-- Elisa and Western Blot
4. Antigen capture
5. Eosinophilia
6. Rectal snips or biopsies
7. Liver biopsy
8. Ultrasound or CT of abdomen
Laboratory
debris in urine
eggs in urine (overnight-millipore)
I.V.P. abnormalities
cystoscopy
serology
Schistosoma Mansoni in the Cecum ( Magnification Colonoscope.)
This 34 year-old male, a routine colonoscopy was
performed a Schistosoma Mansoni was found at the cecum.
Management strategies:
A. Treatment of local irritation (swimmers itch)
B. Treatment of allergic reaction to cercarial
entry (fever, rash, myalgia, pneumonitis Katayama fever)
C. Control of egg laying to prevent complications
D. Treatment of complications
Swimmers itch & Katayama fever:
Anti-allergic (chlopheniramine),
paracetamol, steroids (prednisone or
hydrocortisone)
Control of egg laying & complications:
Praziquantel: Effective against all 3 forms
↑ entry of Ca++ to cell memb, paralyze, detach &
kill
Taken after meal without chewing (bitter)
May increase symptoms of Katayama fever
(↑ allergic reaction due to dead cestodes)
Oxamniquine: Effective only for S. mansoni
Metrifonate: Only for S. haematobium
Outlook (Prognosis
Treatment before significant damage or severe
complications occur usually produces good
results.
Hemospermia
Squamous cell bladder cancer
Sepsis (Salmonella)
Pulmonary hypertension
Cor pulmonale
Neuroschistosomiasis - Transverse myelitis,
paralysis, and cerebral microinfarcts
Infertility
Severe anemia
Low ̶ birth-weight babies
Spontaneous abortion
Higher risk for ectopic pregnancies
End-organ disease
Portal hypertension
Obstructive uropathy
Pregnancy complications from vulvar or
fallopian granuloma
Carcinoma of the liver, bladder, or gallbladder
Prevention
Avoid swimming or bathing in contaminated or
potentially contaminated water
Avoid bodies of water of unknown safety
Snails are an intermediate host for the parasite.
Getting rid of snails in bodies of water used by
humans would help prevent infection.