Schistosomiasis Flashcards
What is the classification of Schistosomiasis?
Blood Fluke (Trematode)
What is the epidemiology of Schistosomiasis
221 million people affected
90% of cases are in Sub-Saharan Africa
17% of children under ten in endemic areas have a degree of liver fibrosis secondary to schisto
What are the three most clinically important trematodes associated with Schistosomiasis? What is there geographical presence?
Shistosoma mansoni - South America, Sub Saharan Africa
Schistosoma haematobium - Sub Saharan Africa
Schistosoma Japonicum - Asia
What snail is the host for S. Haematobium?
Bulinus Spp
What snail is the host for S. Mansoni?
Biomphalaria Spp.
What snail is the host for S. Japonicum
Oncomelania spp.
What is the life cycle of Schistosoma spp.?
- Egg from infected body fluids is deposited into fresh water, where it hatches and releases a miracdia
- Miracidia searches for a snail host and penetrates into the snail
- Within the snail the miracidia develops into a sporocyst
- The sporocyst within the snail develops and eventually releases a cercaria.
- The cercaria releases from the snail and swims freely until it encounters a suitable host
- When it finds a suitable host it burrows into the skin and enters into the blood vessels
- The Cercaria transforms into a schistosomula within the blood vessels of the host and migrates through the body, causing the clinical symptoms associated with schistosomiasis.
- After 4-12 weeks the schistosomula begins to produce eggs, which leads to the chronic stage of infection
How long do adult schistosomes live?
3-7 years (but cases of up to 30 years)
Which species of Schistosomiasis causes the most destruction
Schistosoma japonicum
What causes the most destruction in schistosomiasis? Eggs, Juveniles or adults?
Eggs
Are schistosoma dioeceous or hermaphroditic?
dioeceous. They ‘couple up’ (usually in the liver)
How does schistosomiasis cause destruction?
- Acutely –> damage tissues as adult worms migrate through tissues and blood vessels
- Chronically –> Eggs are meant to pass through and out of the body, but they very often get stuck in vessels or areas where they aren’t meant to; while in the process the release a huge amount of inflammatory secretions, which causes local inflammation –> granuloma formation –> fibrosis and scarring
What are the risk factors for schistosomiasis?
Contaminated water
Repeated exposure to contaminated water (meaning women, children and fishermen are most at risk)
High worm burden
Describe the general presentation of schistosomiasis?
- MIGRATORY PHASE:
- Cercarial Dermatitis (as schistosomula forms)
- Tiredness
- Itch - ACUTE PHASE (Katayama Fever):
- An immune modulated response
- Fever, urticaria, cough (schistosomulae migrate into lung tissue), abdominal pain, Loeffler’s syndrome, hepato-splenomegaly, diarrhoea - CHRONIC PHASE:
- Anaemia, faltered growth, fatigue
Which Schistosoma species are associated with genito-urinary disease?
S. Heamatobium
Which schistosoma are associated with hepato-splenic disease?
S. Mansoni
S. Japonicum
What are the symptoms and complications of Genito-urinary schistosomiasis?
SYMPTOMS
- Haematuria
- FGS –> discahrge, dysparenunia, itch, pelvic pain
-MGS –> change in ejaculate
COMPLICATIONS
- Increased risk of HPV and HIV
- Infertility
- SCC Bladder Ca.
- Obstructive uropathy if granulomas form near bladder outlets
What are the symptoms and complications of hepatosplenic schistosomiasis?
SYMPTOMS:
- Abdominal pain and distension
- hepatosplenomegaly
- ‘Pipe-stem’ Fibrosis
COMPLICATIONS:
- Portal hypertension
- Fulminant liver failure
- GI Haemorrhage from oesophageal varices (usually better outcome than other causes of liver failure, because LFTs remain mostly intact)
- Weight loss
- Failure to thrive
- Reduced cognition
What is Schistosoma Cor Pulmonale?
A complication of S. Haematobium infection
Eggs from the pelvic circulation re-enter into caval circulation and enter into the lungs via cardiac circulation. Here, granulomas form and cause large pockets of lung obstruction –> congestive cardiac disease and pulmonary hypertension
What are ‘common’ sites of uncommon ectopic infections?
- Neuroschistomiasis
- CNS infection in paravertebral venous plexus (Spinal cord compression or CES) or cerebral cortical veins (present as SOL) - Skin
- Peritoneum
- Bone
What are the symptoms and complications of hepatosplenic schistosomiasis?
SYMPTOMS:
- Abdominal pain and distension
- hepatosplenomegaly
- ‘Pipe-stem’ Fibrosis
COMPLICATIONS:
- Portal hypertension
- Fulminant liver failure
- GI Haemorrhage from oesophageal varices (usually better outcome than other causes of liver failure, because LFTs remain mostly intact)
- Weight loss
- Failure to thrive
- Reduced cognition
How is Schistosomiasis diagnosed?
Hepatosplenic:
- Stool Microscopy (Kato-Katz)
- FOB
- RDT faecal calprotectin
- Liver USS
- Colonoscopy
- POCT RDT
Genitourinary
- Urinary reagent strip for haematuria and proteinuria (serum leaks through damaged bladder walls)
- Urine filtration
- Bladder X-ray: Ring-like calcification of bladder (almost pathognomic)
- haematuria questionnaire
- Urine Microscopy
- Urinary CCA/CAA antigen
- Cystoscopy –> calcified bladder walls (from calcified eggs)
What are the challenges with diagnosing schistosomiasis in the acute phase?
- Egg production has only just started, so rarely found on direct examination
- eosinophilia may not be prominent in acute infection
- Serology is only useful after 3 months
What is the best time of day for Schisto Urine Collection
Midday, 10-2pm
Most active time of bladder wall activity apparently
How do you diagnose Schisto in the returning traveller?
- Asymptomatic or symptoms of chronic infection:
After 3 months of return from endemic area
- Eosinophilia
- MSU for RBCs and ova
- Stool for ova
- Serology for schiso antibodies - Symptomatic ACUTE –> rule out malaria and refer to specialist
Can serum antigen tests be used as a test of cure?
No - not reliably reduced once an infection is cleared
How is schisto managed?
- Praziquantal 40mg/kg STAT
- Repeat dose 2-8 weeks after initial dose (re: prazi only kills adult worms)
How can you prevent Schisto?
- MDA –> Praziquantal in all people under 2, including pregnant women >1st trimester
- the most effective preventative measure - Improve water filtration and sanitation (WASH)
- Health education
- Prevent access to transmission sites
- Water chlorination and filtration - Snail Control:
- Niclosamide and other mulloscicides (can negatively affect the rest of the ecology)
- biological snail competitors (expensive and usually insufficient on its own)
- drain lakes
Who does the WHO recommend receive MDA of praziquantal for schistosomiasis?
- If >10% of the population are affected in a given area, provide MDA annually
If >10% of the population are affected in a given area and the incidence is RISING despite adequate MDA coverage consider biannual MDA - If <10% then healthcare facilities should follow a ‘test and treat’ policy
How does the WHO recommend monitoring for schisto in classically endemic areas if there are no reported cases for at least 5 years?
- Test people regularly, regardless of symptoms
- Test local snail populations
- Test random samples of at-risk other mammals
How much of the population must be treated for MDA to be effective?
75%
What might you see on Cystoscopy in S. Haematobium?
On cystoscopy a hyperaemic mucosa with ‘sandy patches’ may be seen
Sandy patches are raised, yellowish mucosal irregularities associated with heavy egg deposition surrounded by fibrous tissue pathognomonic for schistosomiasis.
What are complications of S. Haematobium?
Bladder SCC
Hydronephrosis –> Cardiac failure and LVH
How does Katayama Fever present?
How does Katayama Fever present?
Katayama syndrome usually occurs 2 to 12 weeks after Schistosoma infection.
It is characterized by fever, urticaria and a dry cough sometimes accompanied by a wheeze.
Patchy pulmonary infiltrates or micronodular changes in the lower lung zones may be present on chest radiograph.
Full blood count in the majority of cases shows eosinophilia, but of note, eosinophilia can occur with a delay of several weeks after the onset of symptoms and may be missed.
Most patients recover spontaneously after 2 to 10 weeks.
Rarely, neurological complications can occur, e.g. transverse myelitis, conus medullaris or cauda equina syndrome.
