Ascariasis

Question 1

Ascaris Lumbricoides

Answer 1

• one of most common nematode (roundworm) diseases worldwide
• takes place in the small intestine
• pepsin inhibitor to avoid digestion
• uses muscle contractions to avoid excretion

Question 2

3 egg layers

Answer 2

outer layer: made of protein
Middle layer: made of chitin
inner: protect embryo from digestive enzymes

Question 3

how does it resist digestive enzymes

Answer 3

• body protected by protective epidermis that is enzyme resistant

Question 4

males vs females

Answer 4

males smaller and have curved tail

Question 5

where do they reside

Answer 5

• subcuticular layer of muscle, resistant to muscle contraction forces (peristaltic waves) that push food through GI tract
• feeds on digestive food of host

Question 6

ascaris lumbricoide life cycle

Answer 6

• unfertilized eggs are not infective
• fertilized eggs become infective few weeks after being swallowed
• larvae hatch and are carried to small intestine
• through hepatic portal, transferred towards the lungs where they penetrate alveolar walls, ascend bronchial tree to the throat
• swallowed and enter small intestine again where they mature as adults and mate
• can live in host for 1-2 years
• 2-3 months from infective ingestion to adults in small intestine
• if fever is high in rare cases, adult worms climb up the stomach

Question 7

early phase

Answer 7

• 4-16 days
• blood lung migration phase
• coughing
  fever
• may cause asthma
• high eosinophil count in blood sample

Question 8

late phase

Answer 8

6-8 weeks
- intestinal phase for adults
- abdominal pain and obstruction
diarrhea 
can enter bile duct
mortality

Question 9

Diagnosis

Answer 9

stool test: identify as eggs and larvae in stool sample
- may only appear after few weeks of ingestion

blood test: screen for increased eosinophils

imaging tests

Question 10

ascariasis and the immune response

Answer 10

t helper cells (TH2) release cytokines (interleukins) (IL 4,5,9 etc)

• triggers increase in eosinophil levels and mast cell/basophil activity
• increased smooth muscle cell contractility , elevated globet cell function, increased permeability
• weep and sweep response (decrease fertility?)
• induce iGe production

Question 11

surgery

Answer 11

cut open small intestine, take many worms out

Question 12

menbendazole/albendazole

Answer 12

• interrupts cytoplasmic microtubules in intestinal cells of worms
• inhibits polymerization prevents the from moving
• prevents worm from absorbing glucose
• starvation

Question 13

pyrantel

Answer 13

• nicotinic acetocholine receptor agonist
• spastic muscle paralysis in worms
• poorly absorbed in digestive tract
• worms removed through stool