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Schistosomiasis : Exploring Genomic Information for Control Stephen Gikuru Egerton University-Kenya Irish Forum for Global Health Conference 30 th Nov 2010, NUIM. A public health problem. Neglected parasitic disease that ranks 2 nd to malaria in morbidity.

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Schistosomiasis: Exploring Genomic Information for Control Stephen GikuruEgerton University-KenyaIrish Forum for Global Health Conference 30th Nov 2010, NUIM

a public health problem
A public health problem

Neglected parasitic disease that ranks 2nd to malaria in morbidity.

Despite 50 years of concerted control efforts.

Over 210 million people in 76 countries still infected worldwide.

80% of affected population from Sub- Saharan Africa.

poverty related disease
Poverty related disease
  • Prevalent in tropical and sub-tropical areas.
  • Affects poor communities lacking potable water and adequate sanitation.
  • Children and at higher risk in endemic areas due to play habits.
occupational hazard
Occupational hazard
  • Affects women doing domestic chores in infested water - washing clothes.
  • Also people in occupations in contact with infested water such as fishermen, farmers and irrigation workers.
schistosomiasis parasites
Schistosomiasis parasites
  • Caused by blood flukes of the genus Schistosoma (phylum Platyhelminthes).
  • 3 major human species
    • S. mansoni hepatic & intestinal schistosomiasis
    • S. japonicum
    • S. hematobium urinary schistosomiasis
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S. mansoni- Hepatic/intestinal Schistosomiasis- Africa, Middle East, Caribbean, Brazil, Venuzuela, SurinameS. Japonicum – Hepatic/intestinal Schistosomiasis- China, Indonesia, Philippines.S. haematobium- Urinary Schistosomiasis- Africa, Middle East

Global epidemiology of schistosomiasis(Adapted from CDC)

life cycle of schistosome adapted from cdc
Life Cycle of SchistosomeAdapted fromCDC

Life cyle is Complex – Involves intermediate Snail host and definitive human host.

disease pathology
Disease pathology
  • Schistosome worms can live in vertebrate host for long time without severe manifestations of disease.
  • Female worms live in human portal veins depositing eggs in the intestines or bladder walls.
  • Eggs pass to the gut or bladder lumen and are voided in the faeces or urine.
  • Some eggs are trapped in the liver, intestines, bladder and other tissue sites of host.
disease pathology1
Disease pathology
  • Schistosomiasis pathology due to granulomatous response to eggs trapped in host tissues .
  • Pathology caused by egg-derived antigens.
    • Liver - S. mansoni & S. japonicum
    • Intestine – (hepatic and intestinal schistosomiasis)
    • Bladder - S. haematobium(urinary schistosomisis)
egg in trapped hepatic cells
Egg in trapped hepatic cells

Aggregation of mononuclear cells, neutrophils, basophils, macrophages, lymphocytes.

Adapted from Parasitology Atlas

hepatic granuloma
Hepatic Granuloma

Granuloma formation around the schistosome egg in hepatic cells

Adapted from Parasitology Atlas

hepatic granuloma1
Hepatic Granuloma

Advanced hepatic Granuloma around the parasite egg.

urinary granuloma
Urinary Granuloma

Granulomas around eggs lodged in urinary tract.

slide15

World Health Assembly resolutions WHA54.19 (2001)

Required that by year 2010 regular treatment at appropriate intervals be offered to 75-100% of all school-age children living where schistosomisis, ascariasis, hookworm disease and trichuriasis have public health consequences.

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To control schistosomiasis, there is need for;

  • New drugs
  • Vaccines
  • New diagnostics
  • Snail Vector control
schistosome genomics
Schistosome genomics
  • 1994 WHO established Schistosoma genome sequencing project partnering with TIGR (S. mansoni) and CHGC (S. japonicum).
  • Project aims
    • To promote chemotherapeutic targets
    • and vaccine candidates.
  • 2009 draft sequences of the two parasite have been published.
examples of potential drugs identified using drug repositioning approach berriman et al nature 2009
Examples of potential drugs identified using drug repositioning approach (Berriman et al., Nature ,2009)
benefits of drug repositioning
Benefits of drug repositioning
  • Offers shortened development timelines.
  • Decreased risk as compounds already passed regulatory clinical trials with full toxicological & pharmacokinetic profiles.
  • Significant potential cost savings – important in the context of neglected diseases afflicting the poor
vaccine targets discovery
Vaccine targets discovery
  • Development and deployment of a vaccine is important for control of schistosomiasis.
  • Vaccine candidate must be accessible to host immune system.
  • Surface-exposed or exported.
  • i.e. membrane proteins, e.g. Receptors, some enzymes, ion-binding proteins, immuno-modulatory molecules.
  • Example- tegumental proteins in parasite.
examples of potential vaccine candidates
Examples of potential vaccine candidates
  • Tetraspanins in the outer tegument- function as receptors of for host molecules.
  • Membrane proteins -calpin, annexin, Sm29
biomarkers discovery using metabolomic approach
Biomarkers discovery using metabolomic approach
  • Control of schistosomiasisis relies upon continued surveillance of the disease.
  • Need for a robust diagnostic/prognostic technologies.
  • Use of metabolomics approaches using gene micro-array data.
  • Used identify patterns of biomarkers in parasite genes, proteins, and metabolites.
slide31

Metabolomic approach in diagnostic biomarkers discovery for neglected infectious diseases. (Deneryet al., 2010 )

slide32

This technique has been used successfully to identify 14 diagnostic biomarkers for filariasis (ochorcerciasis)- a neglected parasitic disease.

  • Including - fatty acid/sterol lipid, Protein, hexacosenoic acid, pentacosenoic acid, fatty alcohol/aldehyde .
conclusion
Conclusion
  • Genomic information plays a critical role in offering global insights in pathogenesis of schistosomiasis.
  • It also invaluable in accelerating discovery of new control targets such as drugs, vaccines and diagnostic biomarkers especially for neglected diseases such as schistosomiasis with limited funding.
  • Important tool for scientists in developing world, who need to set the pace in seeking control strategies to these diseases.
acknowledgements
Acknowledgements
  • Combat Diseases of Poverty Consortium (CDPC).
  • Egerton University, Department of Biochemistry & Molecular Biology.

Prof Moses Limo & Dr Paul Mireji

  • Dr Dorcas Yole

Institute of Primate Research, National Museums of Kenya.