Schistosomiasis Flashcards
What are the species that cause schistosomiasis and what is their geographical breakdown?
Schistosoma mansoni- subS African,a Yemen, Egypt, S. America
S. Japonicum- china and Philippines
S. Intercalatum- east and central Africa
S. Haematobium- subS Africa, Egypt, Yemen
How do y u get infected with schistosomiasis?
Cercariae in water penetrate skin
Where do the adult schistoma worms live and how do they get there?
Migrate and pair up in liver then live in venous plexuses of gut or bladder
What is the pathogenesis of schistosomiasis?
Eggs are released but don’t end up in stool or urine, granulomas form around them and become fibrotic
What are the non human stages of the schistoma life cycle?
Eggs in stool/ urine hatch into miracidia in the water and penetrate snails.
Cercariae are then released from snail
What species of snail is a vector for schistoma mansoni?
Biomphalaria
What species of snail is a vector for schistoma haematobium and intercalatum?
Bulinus
What species of snail is a vector for schistoma japonicum?
Oncomelania
Which species of schistoma have eggs in the stool?
Japonicum
Intercalatum
Mansoni
Which species of schistoma have eggs in the urine?
Haematobium
What are the dermal signs of schistosomiasis?
Cercarial dermatitis- itchy red spots where penetration has occurred
What are the features of schistosomiasis in children?
Impaired cognitive development
Stunted growth
Anaemia
Nephrotic syndrome
What is katayama fever?
4-6 wks after exposure to schistosomiasis
Fever, cough, diarrhoea, eosinophilia, hepatosplenomegaly
What are the intestinal sequelae of schistosomiasis and which species cause them?
Mansoni and japonicum
Bloody diarrhoea
Hepatomegaly
Liver fibrosis- PV hypertensionsion- splenomegaly
What causes pathology in schistosomiasis?
The eggs lead to granulomas and then fibrosis
What are the urogenital signs of schistosomiasis and which species causes them?
Haematobium Haematuria Cystitis Obstructive uropathy-> CKD Squamous cell carcinoma Haemospermia Cervix/vulva inflammation-> bleeding
What are the pulmonary sequelae of schistosomiasis?
Pulmonary hypertension-> RV heart failure
What are the neurological sequelae of schistosomiasis?
Japonicum - lesions in brain
Mansoni and haematobium -in spinal cord
Very rare
What does the mansoni egg look like?
Lateral spine
150microm
What does the japonicum egg look like?
Round and often can’t see small spine
90 microm
What does the haematobium egg look like?
Terminal spine
145 microm
What does the intercalatum egg look like?
Terminal spine, central bulge
100-200 microm
How do you diagnose schistosomiasis?
Stool and urine parasitology but low sensitivity
Urine POC circulating catholic antigen for mansoni
IgM/IgG antibody but can’t tell acute so not useful in endemic
Hatching- hatch eggs into miracidia, can use larger sample so more sensitive
PCR
How do you treat schistosomiasis?
Praziquantel single dose
No severe organ damage reversal
How do you prevent schistosomiasis?
Mass drug administration based on prevalence
Water sanitation, don’t stand in water to wash
Education
Chemicals to kill snails or release fish that eat them
