Hydatid disease - Echinococcus granulosus

Hydatid disease - Echinococcus granulosus

1. Background

   • tapeworms
     • 3 segments
     • uterus - 500-1500 eggs
   • v small - 2-7mm
   • DEFINITIVE HOST = DOG
     • high levels of tapeworm
     • can survive a long time in environment
   • INT. HOST = BROAD RANGE
   • zoonotic disease

2. life cycle

   • irregular dispersion and contamination of areas
   • additional dispersion through vectors and other factors
   • highly resistant eggs
   • susceptible for dryness
   • metacestodes
     • burrow through intestinal wall
     • migrate through host
     • form hydatid cysts in int host only
       • incubation time - month to a year
         • sheep - liver and lung
         • cattle - lungs
         • horses - liver
         • humans - liver 70%, lungs 10-20%, other <10%
     • asexual reproduction
       • hydatid sand
         • protoscoleces = grains
           • attaches to intestine - protoscolex evagination
   • PPP - 6 WEEKS
     • PATENCY - 6 MONTHS

3. prevalence

   • UK - Wales
     • <98% sheep
     • humans - low numbers
     • high levels of infection

4. control

   • boundaries between dogs and sheep
   • wormer treatment
   • education
   • investigate epidemiology
   • regular screening

5. strains

   • diverse strains
     • different infectivity
     • common = DOG IS DEF HOST
     • most zoonotic except horse strain
   • sheep strain is classic strain
     • sheep = main int host
       • eggs can infect cattle and humans