Schistosomiasis
Neena Davisson
March 15, 2012
Schistosomiasis is a
parasitic infection
• Schistosomiasis is
caused by a
trematode helminth
Schistosomiasis is an ancient disease
Schistosome eggs have been recovered
from both Chinese and Egyptian mummies
Schistosomiasis is an ancient disease
Hieroglyphics also refer to the disease.
Schistosomiasis is prevalent in tropical
and sub-tropical areas
Schistosomiasis is commonly found in areas
without safe water and good sanitation. At-risk
groups include…
• Agricultural and fishing
populations
Schistosomiasis is commonly found in areas
without safe water and good sanitation. At-risk
groups include…
• Agricultural and fishing
populations
• Women performing
domestic chores
Schistosomiasis is commonly found in areas
without safe water and good sanitation. At-risk
groups include…
• Agricultural and fishing
populations
• Women performing
domestic chores
• Irrigation workers
Schistosomiasis is commonly found in areas
without safe water and good sanitation. At-risk
groups include…
• Agricultural and fishing
populations
• Women performing
domestic chores
• Irrigation workers
• Refugees
• “Off track” tourists
…but schistosomiasis is largely a disease
of children.
Urinary schistosomiasis
affects 66 million children
throughout 54 countries.
Schistosomiasis causes great morbidity and
mortality in the developing world
• > 200 million people
are infected worldwide,
600 million at risk
Schistosomiasis causes great morbidity and
mortality in the developing world
• > 200 million people
are infected worldwide,
600 million at risk
• 85% of infections in
sub-Saharan Africa
• About 280,000 die every
year from infection
Schistosomiasis causes great morbidity and
mortality in the developing world
• > 200 million people are
infected worldwide, 600
million at risk
• 85% of infections in subSaharan Africa
• About 280,000 die every
year from infection
• Morbidity – growth
stunting, cognitive
impairment, hepatic
fibrosis, urinary
obstruction, cancer
There are two forms of Schistosomiasis
Acute
• Rash (Swimmer’s itch)
• Fever
• Cough
• Chills
• Muscle aches
There are two forms of Schistosomiasis
Chronic
Acute
• Rash (Swimmer’s itch)
• Fever
• Cough
• Chills
• Muscle aches
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Abdominal pain
Ascites
Enlarged liver
Splenomegaly
Blood in stool
Diarrhea
Hematuria (blood in urine)
Dysuria (painful urination)
Varicose veins
Seizures
Paralysis
Biopsy is the primary method of
diagnosing schistosomiasis
• Use fecal smears and
urine tests to visualize
schistosome eggs
Children infected with schistosomiasis
show vials of blood-red urine.
Biopsy is the primary method of
diagnosing schistosomiasis
• Use fecal smears and
urine tests to visualize
schistosome eggs
• Blood in urine can be
detected using
chemical reagent strips
Children infected with schistosomiasis
show vials of blood-red urine.
Blood tests also help confirm diagnosis
but…
• Positive results may
only indicate past
exposure
Blood tests also help confirm diagnosis
but…
• Positive results may
only indicate past
exposure
• Tests are not positive
until the patient has
been infected for 6-8
weeks
Some other diagnostic methods
• For tissue biopsy in case no eggs are found in fecal or
urine samples:
• Colonoscopy
• Endoscopy
• Liver biopsy
Some other diagnostic methods
• For tissue biopsy in case no eggs are found in fecal or
urine samples:
• Colonoscopy
• Endoscopy
• Liver biopsy
• To measure extent of infection:
• MRI
• CT
• Ultrasound
• Chest x-rays
• Echocardiograms
How was schistosome parasite
discovered?
Theodor Bilharz
1825-1862
"After my attention had been drawn to the liver, I soon found a white long helminth in
the blood of the portal vein in quantity, which I assumed to be a nematode but which
I immediately recognised as something new. The microscope revealed a splendid
distomum with a flat body and a curving tail which exceeded the body about ten
times in length...”
The Life Cycle of the Schistosome
relies on two hosts
The Life Cycle of the Schistosome relies
on two hosts
• Intermediate host: snail
• Definitive host: human
• Adult stages have two
sexes
There are many forms of schistosomes
that cause disease in humans
• S. mansoni – causes intestinal schistosomiasis and is
prevalent in 52 countries of Africa, the Caribbean, the
Eastern Mediterranean and South America
There are many forms of schistosomes
that cause disease in humans
• S. mansoni – causes intestinal schistosomiasis and is
prevalent in 52 countries of Africa, the Caribbean, the
Eastern Mediterranean and South America
• S. haematobium – causes urinary schistosomiasis and
affects 54 countries in Africa and Eastern Mediterranean
There are many forms of schistosomes
that cause disease in humans
• S. mansoni – causes intestinal schistosomiasis and is
prevalent in 52 countries of Africa, the Caribbean, the
Eastern Mediterranean and South America
• S. haematobium – causes urinary schistosomiasis and
affects 54 countries in Africa and Eastern Mediterranean
• S. japonicum – causes intestinal schistosomiasis in the
Pacific region (aka ‘Katayama’ disease)
There are many forms of schistosomes
that cause disease in humans
• S. mansoni – causes intestinal schistosomiasis and is
prevalent in 52 countries of Africa, the Caribbean, the
Eastern Mediterranean and South America
• S. haematobium – causes urinary schistosomiasis and
affects 54 countries in Africa and Eastern Mediterranean
• S. japonicum – causes intestinal schistosomiasis in the
Pacific region (aka ‘Katayama’ disease)
• S. mekongi – causes intestinal schistosomiasis in 7
African countries
There are many forms of schistosomes
that cause disease in humans
• S. mansoni – causes intestinal schistosomiasis and is
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prevalent in 52 countries of Africa, the Caribbean, the
Eastern Mediterranean and South America
S. haematobium – causes urinary schistosomiasis and
affects 54 countries in Africa and Eastern Mediterranean
S. japonicum – causes intestinal schistosomiasis in the
Pacific region (aka ‘Katayama’ disease)
S. mekongi – causes intestinal schistosomiasis in 7
African countries
S. intercalatum - found in 10 African countries
Infection induces T-cell response
• Increase in TNF, IL-1
and IL-6
• Granuloma formation
How do we treat schistosomiasis?
• First line drug:
Praziquantel
• Treats all forms of
schistosomiasis
• No side effects
How do we treat schistosomiasis?
• First line drug:
Praziquantel
• Treats all forms of
schistosomiasis
• No side effects
• Oxamniquine
• Intestinal
schistosomiasis
How do we treat schistosomiasis?
• First line drug:
Praziquantel
• Treats all forms of
schistosomiasis
• No side effects
• Oxamniquine
• Intestinal
schistosomiasis
• Metrifonate
• Urinary schistosomiasis
Praziquantel may target the parasite’s
calcium ion channels
• Mechanism and target
is unknown
Praziquantel may target the parasite’s
calcium ion channels
• Mechanism and target
is unknown
• Causes severe
spasms and paralysis
of worms’ muscles
caused by influx of
Ca2+ ions
Praziquantel may target the parasite’s
calcium ion channels
• Mechanism and target
is unknown
• Causes severe
spasms and paralysis
of worms’ muscles
caused by influx of
Ca2+ ions
• Metabolized through
cytochrome p450
pathway via CYP3A4
Praziquantel has many limitations
• Ineffective against
juvenile schistosomes
Praziquantel has many limitations
• Ineffective against
juvenile schistosomes
• Develops resistance
• Resistant strains in
Egypt and Senegal
Resistance to S. japonicum
Praziquantel has many limitations
• Ineffective against
juvenile schistosomes
• Develops resistance
• Resistant strains in
Egypt and Senegal
• High rates of
reinfection
Resistance to S. japonicum
Praziquantel has many limitations
• Ineffective against
juvenile schistosomes
• Develops resistance
• Resistant strains in
Egypt and Senegal
• High rates of
reinfection
• Cannot be taken by
HIV/AIDS patients on
Rifampin (inhibits
CYP3A4)
Part of the treatment plan needs to
include prevention strategies
• Health
education/hygiene
• Installation of safe
water supply
Part of the treatment plan needs to
include prevention strategies
• Health
education/hygiene
• Installation of safe
water supply
• Treatment of water
supply with
molluscicides
Part of the treatment plan needs to
include prevention strategies
• Health
education/hygiene
• Installation of safe
water supply
• Treatment of water
supply with
molluscicides
• Vaccine – not yet
developed
Works Cited
• Griffiths, Jeffrey. "MPH/CEE241 Biology of Water and Health, Fall
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2007 - Tufts OpenCourseWare." Tufts University, 2008. Web. 2 Mar.
2012. http://ocw.tufts.edu/Content/55/lecturenotes/703050/703095
"Parasites - Schistosomiasis." Centers for Disease Control and
Prevention, 02 Nov. 2010. Web. 2 Mar. 2012.
http://www.cdc.gov/parasites/schistosomiasis/biology.html
Pearce, Edward J., and Andrew S. MacDonald. "The Immunobiology
of Schistosomiasis."Nature Reviews 2 (2002): 499-511. 2002. Web. 2
Mar. 2012.
"Schistosomiasis." MicrobiologyBytes, 28 Jan. 2007. Web. 2 Mar.
2012. http://www.microbiologybytes.com/introduction/Schisto.html
"Schistosomiasis." World Health Organization, Jan. 2012. Web. 2
Mar. 2012. http://www.who.int/mediacentre/factsheets/fs115/en/
Stewart, Terry. "SRG Introduction to Schistosomiasis." University of
Cambridge: Department of Pathology, 2010. Web. 2 Mar. 2012.
http://www.path.cam.ac.uk/~schisto/schistosoma/index.html