Schistosomiasis

Question 1

Global burden of disease

Answer 1

Estimated 200 million people infected worldwide

600 million people at risk

85% of people infected live in the african continent

Morbidity and mortality estimates vary

GBD update 2019 estimated schistosomiasis attributable deaths at 11,500 and DALYS at 1.64 million

Question 2

Geographic distribution

Answer 2

S. mansoni (intestinal schistosomiasis) in sub-
Saharan Africa, South America (Brazil, Venezuela,
Suriname), Caribbean & Arabian Peninsula

S. haematobium (urinary schistosomiasis) in Africa &
Middle East

S. japonicum in China, Philippines, Sulawesi
(eliminated from Japan)

S. mekongi in parts of Cambodia and Laos.

S. intercalatum in DRC

S. guineensis in West Africa

Question 3

Who is at risk of schistosomiasis?

Answer 3

Contact with contaminated freshwater sources
- All ages
- Fishing populations/people living and working along rivers and lakes
- Gender patterns vary
- Travelers

Question 4

Reservoir hosts for schistosomiasis

Answer 4

Humans

S.mansoni: rodents, baboons

S.japonicum: horse, dogs, cattle, rodents, goats, pigs

Question 5

Acute pathology

Answer 5

Swimmers itch, urticarial rash at sites where schists have entered
Katayama fever (S.japonicum, tourists)
- Fever, fatigue, myalgia, malaise, cough
- Eosinophilia, patch infiltrates on CXR

weeks to months after exposure
spontaneous recovery
may developw ith abdominal symptoms - weight loss, diarrhoea, diffuse abdominal toxaemia, dysponea, hepatosplenomegaly, rash

Question 6

Chronic patholgy

Answer 6

Pathology related to eggs in tissue
- Perivesical/ peri-intestinal migration
- Liver, spleen, lungs, cerebrospinal system
- Eosinophilic inflammatory / granulomatous reactions

Question 7

Urogenital schistosomiasis

Answer 7

S. haematobium, Bulinus snail vector
Primarily affecting vesical and ureteral walls
Dysuria, proteinuria, haematuria- blood in urine (months)
Bacterial infections, bladder stones
Fibrosis, calcification of bladder wall
Hydroureter, hydronephrosis
Kidney disease
Squamous bladder cancer (chronic)

Genital schistosomiasis (female)
- Complications can lead to infertility and preganancy loss, associated with increased risk of HIV transmission

Question 8

Intestinal schistosomiasis

Answer 8

S. mansoni, Biomphalaria snail

Also S. japonicum (Oncomelania snail, S.
mekongi, S. intercalatum

Affecting intestinal wall
- S. mansoni in inferior mesenteric veins
(large bowel, rectum)
S. japonicum in superior mesenteric
veins (small intestine)
S. intercalatum/ S. guineensis inferior
mesenteric plexus

Mucosal granulomatous inflammation,
pseudopolyposis, micro-ulcerations, bleeding

Question 9

Hepatic schistosomiasis

Answer 9

S. mansoni, S. japonicum, S. mekongi
- Early reaction: inflammatory
- Eggs in periportal spaces of liver

Causes hepatomegaly (80% of infected children)
Chronic (years): fibrotic
- Long-standing infections/re-infections
- Young/ middle-aged adults
- Periportal collagen deposits àfibrosis à
occlusion of portal veins
Portal hypertension, splenomegaly, collateral
venous circulatory, portocaval shunting,
gastrointestinal varices

Question 10

Neuroschistosomiasis

Answer 10

• Involvement of CNS
• Rare
• S.mansoni, haematobium, japonicum
• Spinal cord – s.mansoni and s.haematobium
• Acute schistosomal encephalopathy, pseduotumoral encephalic schistosomiasis (s.japonicum)
• Usually in non-immune people

Question 11

Clinical features of S.haematobium

Answer 11

Haematuria

Pseudopapillomas/ tumours in bladder mucosa

Can develop squamous cell bladder carcinomas

Bladder calcification (XR) as a result of chronic haematobium infection

Obstructive uropathy (granulomas near/ in ureters)
- Hydrourete

Genital schistosomiasis
- Urethral papillomatous lesions
- Female genital schistosomiasis

Cor pulmonale
- Obstruction in pulmonary arterioles
- Pulmonary hypertension, right ventricular hypertrophy, congestive heart failure.

Question 12

Clinical features of S.mansoni

Answer 12

Often few/no symptoms
Anaemia
Pseudopolyposis of the colon
- Papilloma-like, may ulcerate/bleed

Liver fibrosis
- Portal hypertension
- Hepatosplenomegaly
- Bleeding oesophageal varicies
- Liver function maintianed until late stages
- Ascites not common until later stages (albumin maintained)

Question 13

Clinical features of S.japonicum

Answer 13

More similar to S.mansoni

More severe

Katyama fever

Question 14

Direct diagnostics

Answer 14

S.haematobium
- Urine (10am to 2pm)
- Sedimentation/filtration

S.mansoni/ S.japonicum
- Stool
- Concentration – Kato Katz smear

Rectal biopsy
- Histology

Question 15

Indirect diagnosis

Answer 15

Circulating antibodies/antigens in blood/urine
- S.mansoni, CCA (circulating cathodic antigen) test

S.haematobium
- Haematuria (frank, dipstick)
- XR: ring like calcification of bladder
- Ultrasonography: obstructive uropathy

S.mansoni/S.japonicum
- Ultrasonography of liver
- Pipestem fibrosis

Neuroschistosomiasis
- Brain imaging: MRI

Question 16

Treatment of schistosomiasis

Answer 16

Praziquantel (acts on adult worm)
- BNF, unlicensed

S.haematobium and S.mansoni worm infections
- Adult, oral, 20mg/kg, followed by 20mg/kg after 4-6 hours

Schistosoma japonicum worm infections
- Adult, oral, 20mg/kg 3 times a day for 1 day

Artemisinin derivatives (malaria) act on juvenile stages of worms
- Nb. Co-endemicity malaria – schistosomiasis

Management of complications

Question 17

What is primary, secondary and tertiary prevention?

Answer 17

Primary prevention – prevent onset of
disease/ill-health

Secondary prevention – early diagnosis and
treatment to prevent development of disease

Tertiary prevention – prevent complications

Question 18

Preventative measures

Answer 18

Safe water and sanitation associated with lower
odds of schistosomiasis (Grimes et al 2014)

Snail control (Sokolow et al, 2016, 2018)
- Molluscicide
- Biological control

Access to treatment
- Vertical programmes
- Health system strengthening

Question 19

Mass drug administration

Answer 19

To reduce burden of disease

School children in endemic areas (75%), and adults in at risk communities (fishing)

Praziquantel (schistosomiasis) and
Albendazole (STH), once a year, free administered through Ministry of Health

Administered by voluntary community
distributors

Question 20

Mass drug administration challenges

Answer 20

Logistics
Resistance to vertical interventions
- Lymphatic Filariasis mda in Tanzania (Parker
et al 2008)

Local perspectives
- Biomedical understandings of disease and the rationale for control programme
- Local perceptions and understandings of the disease and rationale for control
programme