Ascaris Lumbricodes Flashcards
Describe the adult morphology of ascaris
Cylindrical and tapered at both ends
Tail curved into a semicircle( males ) or straight in females.
Pale yellow or brown with white longitudinal lines
Describe the egg morphology of ascaris lumbricoides Fertilized egg:
Fertilized egg: rounded thick shell with an external mamilated layer that normally stains brown by the bile pigment, egg can be decorticated, 4-75um in length
Unfertilized egg morphology:
Elongated, larger than fertilized egg( UpTo 90um)
Thinner shell
Mamilated layer is more variable
Describe the difference between male and female ascaris
Male Female
1.Body smaller, short and
thin
2. Tail end coiled Tail end straight
3. Anus and genital pore separate
are common
4. Penile specules and papilae absent
are near post opening
5.absent Reproductive
pore - post1/3
6. Rep organ- one straight Rep organ 2
tube tubes in Y structure
Describe the life cycle of of ascaris lumbricoides
Infection begins with ingestion of embryonated infection> eggs hatch in the small intestine and larvae migrate through the gut wall> pass through circulation and migrate to the lungs > larvae further mature in the lungs, penetrate the alveoli walls and ascend the bronchial tree where they are swallowed> Live in the intestinal lumen but do not attach to the wall and derive their sustenance from food , they develop into adults > female produces eggs > passed into faeces
The largest intestinal nematodes are ?
Ascaris lumbricoides
Giant round worms ( ascaris) migrate to?
Lungs
Appendix
hepatobiliary system
Pancreatic ducts
Rarely kidneys and brain
Egg ingestion and passage takes approx how many weeks?
9
During the time of pulmonary symptoms eggs are not shed. Explain relevance.
This makes diagnosis via still OVAs and parasites not possible
Mode of transmission of ascaris
Fecal oral transmission
Taking contaminated food and water
In children- eat dirt
Failure to wash hands.
Adult worm live in the intestines for how long? Relevance.
6-24 months
They can cause bowel obstruction in large numbers- surgery
The pathogenesis of ascaris is attributed to :
Host immune response
Effects of larval migration
Obstruction and mechanical disruption by adult worms
Nutritional deficiency associated with worm burden
Pathology of ascaris lumbricoides
Early phase- respiratory system result from larval migration
loeffler syndrome
Late phase - GIT symptoms may occur and are more related to mechanical effects of high parasitic loads
Early phase and late phase timelines :
EP: 4-16 days after egg ingestion
LP: 6-8weeks after ingestion of egg
Describe Loeffler syndrome
Caused by migration of larva through the lungs.
Symptoms occur in settings of eosinophilic pneumonia
Fever
Non productive cough
Dyspnea- laboured breathing
Wheezing
