schistosomiasis bilharzia

schistosomiasis bilharzia

1. cercarie penetrates skin

   • cercaria is the free swimming infective stage
   • tail is lost during penetration
     • gercariae migrate via the blood circulation to the liver of the host and mature
       • adult female with adult male inside
         • adults migrate t blood vessels of intestine or bladder
           • eggs are laid and appear in faces or urine
             • different subspecies have different shape of eggs
               • eggs enter fresh water
                 • miracidium hatches from eggs
                   • penetrates into snail tissue
                     • snail portion of life cycle
                     • sporocyst in snail: 2 generations
                       • developing carcariae

2. egg-fences or urine > miracidium-water > sporocyst- snail > cercariae > schistosomulum- skin > adult -ceins of intestine or bladder

3. S. japonica infers many domestic animals

   • eggs and granuloma in liver causes portal hypertension

4. S haematobium

   • adults also found in veins of vagina
   • eggs and granulomata cause sandy grainy patches noticeable to clinicians
     • extensive granulomata leads to vein friability and changes in vaginal mucosa
       • this results in increased suceptabilitto HIV

5. control

   • control intermediate hosts
     • water content: damns and irrigation canals
   • few drugs available
     • best: praziquantel
   • natural resistance to IgE antibodies and Th2
   • parasitic population are highlypolymorphic

6. trichobilharzia sp: causes swimmers itch