ascaris lumbricoides

ascaris lumbricoides

1. most common human helminthic infection

2. worldwide distribution

   • most prevalent in tropical and subtropical areas and areas with poor sanitation

3. largest nematode that can parasite the human body

   • adult females grow to 20-35 cm
   • adults males
     • 15-30 cm

4. female may produce 200,000 eggs per day

   • after fertilisation eggs embryonate and becomee infective after 18 days to several weeks

5. eggs

   • highly robust
   • they are swallowed
     • larvae hatch
       • invade the intestinal mucosa
         • they are carried by portal and circulation to lungs
           • larvae mature further in the lungs: 10-14 days
             • they then penetrate the alveolar walls
               • they then ascend the bronchial tree to the throat and are swallowed

6. between two and three months required between ingestion of the infective eggs and female oviposition

7. adult worms live 1-2 years

8. loafers syndrome

   • type 1 immune hypersensitivity
   • IgE antibody levels associated with natural immunity