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1. Schistosomes

2. STRUCTURE
• Electron microscope studies by Ford and
Blankespoor (1979) showed the different egg
morphologies.
• The eggs produced by adult female worms
are characteristic for each species.
• Eggs have distinct morphological features,
including spines.
• S. mansoni egg shows a prominent lateral
spine.
• S. haematobium presents a terminal spine.
• S. japonicum eggs present only a
rudimentary spine/absence.

3. STRUCTURE
• S. haematobium, S. japonicum, and S. mansoni are all parasitic flatworms
known as blood flukes.
• The adult worms of all three species: Elongated and flattened in shape
Bilaterally symmetrical
Dioecious - with separate male and
female individuals.

4. STRUCTURE
• Schistosomes have a rudimentary digestive system, as they primarily absorb
nutrients through their tegument (outer covering) from the host's blood.
• The life cycle involves stages in both an intermediate host (freshwater
snails) and the definitive host (humans).

5. PROPERTIES
• Host Specificity: Each Schistosoma species
has a specific range of hosts.
• Schistosoma haematobium primarily infects
the urinary system.
• Schistosoma japonicum and Schistosoma
mansoni typically infect the intestinal system.
• Immunoevasion Mechanisms: Schistosomes
have evolved various mechanisms to evade
the host immune response, including
antigenic variation and modulation of host
immune cells.

6. PROPERTIES
• Variability in Clinical Manifestations: The clinical manifestations vary between
species, with each causing different patterns of disease.
• Geographic Distribution: The distribution of each species is influenced by
environmental factors, including the presence of suitable freshwater snail
hosts.
• Drug Susceptibility: Praziquantel is the primary drug used for the treatment of
schistosomiasis caused by these species, but variations in drug susceptibility
may exist.

7. EPIDEMOLOGY
• Schistosoma species are flatworms
and underlying etiology of
schistosomiasis, which is a parasitic
disease that, after MALARIA.
• The prevalence of the illness is
approximated to be over 200 million
cases and 100000 deaths yearly.
• The 2 major forms of schistosomiasis
- Intestinal (S. mansoni and S.
japonicum) Urogenital (S.
haematobium).

8. EPIDEMOLOGY
• S. mansoni - Geographical distribution –
Africa, Brazil, Venezuela and The Caribbean.
• S. japonicum - Geographical distribution -
China, Indonesia, Philippines.
• S. haematobium - Geographical distribution -
Africa, the Middle East, Corsica (France).

9. Schistosoma
haematobium
• Primarily found in the venous plexus of the
urinary bladder.
• Eggs are characterized by a terminal spine.
• The presence of these spines is a key
diagnostic feature.
• Intermediate Host: Freshwater snails of the
genus ‘Bulinus’ serve as the intermediate host.
• Infection occurs through direct contact with
contaminated freshwater, usually during
activities such as swimming, bathing, or
washing.

10. Schistosoma japonicum
• Found in the mesenteric veins of the
intestine.
• Eggs have a more lateral spine (off-
center spine).
• Freshwater snails of the genus
‘Oncomelania’ serve as the
intermediate host.
• Human infection occurs through contact
with contaminated freshwater, and
activities like agriculture, fishing, or
washing in infested water sources

11. Schistosoma mansoni
• Resides in the mesenteric veins of the intestine, particularly the large
intestine.
• Eggs have a lateral spine similar with S. japonicum, but it is more pronounced
and larger.
• Freshwater snails of the genus ‘Biomphalaria’ serve as the intermediate host.
• Infection occurs through contact with freshwater contaminated with cercariae,
the larval stage of the parasite. Activities such as bathing, swimming, or
washing in contaminated water can lead to transmission.

13. Pathogenesis
• The cercariae penetrate the skin of humans.
• The larvae then migrate through the bloodstream to the liver, where they
mature into adult worms.
• The adult worm mate and produce eggs, which are then released into the
environment through human urine or feces.
• The eggs hatch in water, and the resulting larvae (cercariae) infect snails,
completing the life cycle.

14. Pathogenesis
• Schistosome infection presents the host with a complex challenge.
• Adult worms do not replicate in the host but produce hundreds of thousands of
eggs over a life span of 4–7 years. Eggs retained in the host tissue survive for
up to 6 weeks.
• Granulomatous response against ova of Schistosoma that are entrapped
within the host's liver contributes to fibrosis.
• Host reactions are therefore complicated by these overlapping parasite
factors, which result in a myriad of immunologic and nonimmunologic
responses.

15. IMMUNITY
• Innate Immune Response:
Skin Penetration: The innate immune system is activated.
Macrophages and Neutrophils: Attempting to engulf the
parasites.
Inflammatory Response: The process induces an
inflammatory response.
• Adaptive Immune Response:
Th1/Th2 Response - T Cells - Antibody Production –
Eosinophils.

16. IMMUNITY
• Central to the cause of disease is the cell-mediated granuloma formation and
multiple humoral and cellular regulatory responses.
• Resistance to infection with any schistosome species is both innate and
acquired.
• The role of each in regulating parasite populations is still being examined.
Population-based studies suggest strongly that acquired immunity exists in
humans.

17. • Schistosoma haematobium (Urogenital
Schistosomiasis):
• Blood in the urine is a hallmark symptom. It
occurs when adult worms reside in the blood
vessels surrounding the bladder and ureters,
leading to irritation and damage to these tissues.
• Dysuria: Painful urination may occur.
• Urinary Tract Damage: Chronic infection can
lead to fibrosis, scarring, and calcification of the
bladder and ureters.
• Hydronephrosis: Severe cases may result in the
dilation of the kidneys due to obstruction.

18. Clinical manifestations
• Schistosoma japonicum (Intestinal Schistosomiasis):
• Abdominal Pain: Pain in the abdominal region is
common.
• Diarrhea: Chronic infection can lead to chronic diarrhea.
• Hepatosplenic Disease: In advanced cases, the liver and
spleen may become enlarged, leading to hepatosplenic
schistosomiasis.
• Portal Hypertension: Severe cases can result in portal
hypertension, with potential complications like ascites
and esophageal varices.

19. Clinical manifestations
• Schistosoma mansoni (Intestinal
Schistosomiasis):
• Abdominal Pain: Pain in the abdominal region,
especially around the liver and Intestines.
• Diarrhea: Chronic infection can lead to chronic
diarrhea.
• Hepatosplenic Disease: Similar as S.
japonicum, chronic infection may result in
hepatosplenic involvement.
• Portal Hypertension: Severe cases can lead to
portal hypertension, with potential
complications.