Schistosomiasis

Question 1

What is schistosomiasis?

Answer 1

Caused by blood-flukes (trematode worms) of the genus Schistosoma.

Disease develops after contact with contaminated freshwater such as swimming and washing.

Symptoms are due to an immune complex response to the migrating parasite (Katayama syndrome) or deposition of parasite eggs in body tissues.

Question 2

Explain the schistosomiasis life cycle.

Answer 2

Snails releases infectious schistosome cercariae into fresh water.

Cercariae penetrate human skin.

Immature schistosomes migrate through body.

Schistosome maturation

Adult worms mate and produce eggs

Eggs released in urine or stool

Eggs hatch in fresh water

Snails are infected

And it goes on.

Question 3

Presentation of schistosomiasis.

Answer 3

50% are asymptomatic or have unspecific symptoms.

Question 4

What are the clinical syndromes of schistosomiasis?

Answer 4

Larval penetration

Migration of schistosomules

Host response to egg deposition

Question 5

Explain clinical presentation of larval penetration.

Answer 5

Pruritic papular rash also called swimmer’s itch.

Question 6

Clinical presentation of migration of schistosomules.

Answer 6

Leads to Katayama syndrome 2-8 weeks after exposure.

Fever, urticaria, diarrhoea, cough, wheeze, hepatosplenomegaly, eosinophilia.

Question 7

Clinical presentation of host reponse to egg deposition.

Answer 7

Intestinal = Pain, diarrhoea, blood in stool, granulomatous hepatomegaly, splenomegly, bower perforation, hyperplasia, polyposis, liver fibrosis, portal HTN, varices.

Urogenital disease = haematuria, dysuria, ureteric fibrosis, hydronephrosis, CKD, bladder fibrosis/cancer, genital lesions, vaginal bleeding, dyspareunia, vulval nodules, haemospermia, prostatitis.

Lung disease = Pulmonary HTN and cor pulmonale

CNS disease = Rare, acute lower limb paraplegia, transverse myelitis.

Question 8

Diagnosis of schistosomiasis.

Answer 8

Ova in urine or faeces

Serology for egg antigen however will be negative in Katayama’s.

Bowel/bladder histology

Bladder calcifications on AXR

Renal obstruction

Hydronephrosis on USS

Question 9

Treatment of schistosomiasis.

Answer 9

Two doses of praziquantel 20mg/kg PO seperated by 4h.

Steroids for Katayam fever.

If eosinophilic after 3 months after treatment look for other helminths.