Schistosoma

Schistosoma

1. Infection caused by infection parasite trematode helminthes of genus schistosoma

   • Schistosoma haematobium
     • Africa
       • invades basement membrane of bladder
         • excreted in urine
     • BULINUS
     • no animal reservoirs
   • schistosoma japanicum
     • japan
     • Oncomelania
       • basement membrane of intestine
         • excreted in feces
     • can reside in dogs and cats
   • schistosoma.mansoni
     • rural areas of Brazil and Africa
     • BIOLAMPHALARIA
     • no other vertebrate host
   • human infection-swimming or bathing with cercariae
     • slow moving bodies of water
     • contain the intermeadiate host snail
   • Epidemiology
     • 200 million at risk
     • 120 symptomatic
     • mortality 280,00 per anum
     • WHO
     • endemic in over 70 countries
   • simple life cycle from intermediate host(snail) to human host
     • excretion of feces/urine into slow bodies of water
     • 2 conditions
       • snail/ humanmoving through same body of water
       • Humans must wee/poo in water
         • sometimes same villages use same water source
           • spread of infection
           • downstream effect
           • because of demand transmission increased
       • conditions essential to maintain lifecycle
     • Life cycle
       • defication/urination/pump feces/urine into water
         • eggs develop miracidia
           • seek out intermediate snail host
             • penetrate snail tissue
               • asexual reporduction occurs in snail
                 • mircidia develop into circariae
                   • swim seek out human host
                     • infect human by penetration
                       • lose forked end convert anerobic resp
                         • schistosomula develop and migrate portal system
                           • trasnform to adult worms
                             • need to seek out a mate
                               • female attaches to male
                                 • release eggs
                                   • eggs released burrown endothelium
                                     • migrate to venules of bladder
                                       • penetrate basment membrane
                                       • migrate to large intestine
                                       • excreted in feces or urine
                             • deecious
                               • male worms much smaller than female
                                 • gynecophoral canal ridge
                                   • female locates in here
                                     • produce eggs
                   • long thin and have forked end
     • Pathology
       • initially swimmers itch
       • may get fever, puritis, localised odema
       • dependent on phase infestion
       • immunity of individual
       • large invasions fever, chills, spleen, liver enlargement
       • Months pass and individual is fine
         • asymptomatic
         • acute phase steps up
           • mature flukes lay eggs
             • mesenteric venules
               • fever, abdominal pain
               • hypertension
             • graulomas
               • eggs lodge in small vesicles
             • hepatospelnomagly
             • lymphadenopathy
       • bowell cancer

2. Treatment

   • antihelmniths
     • prevents growth of worms in body
     • Praziquantal
       • effective for all schistosoma
     • Oxammiquine
       • cheaper
       • used on mass
       • targets adult worms