SchistosomiasisNeena DavissonMarch 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 diseaseHieroglyphics 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 sub-Saharan 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

Acute

• Rash (Swimmer’s itch)• Fever• Cough• Chills • Muscle aches

Chronic

• 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 Schistosomerelies 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 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 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