L17: Secernetea 2 Flashcards
What is the causal agent of Ascariasis
Ascaris lumbricoides is the largest and most common nematode (roundworm) parasitizing the human intestine.
Adult females: 20 to 35 cm; adult male: 15 to 30 cm
Worms possess a 3-lipped mouth
What is the geographic distribution of A. lumbricoides
The most common human helminthic infection
1200M infections worldwide
DALY = 10.5M years (2nd most important intestinal nematode infection after hookworms
HW + Trichuris + Ascaris have a combined DALY of 39.0M years (approaching malaria)
Highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation.
Occurs in Jamaica (<10%)
Describe the lifecycle of A.lumbricoides
https://www.youtube.com/watch?v=lZHUR8XxoZw&ab_channel=MedicalMicrobiologyGuide
List the clinical features of Ascaris
Although infections may cause stunted growth, adult worms usually cause no acute symptoms.
During the lung phase of larval migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis i.e. Loeffler’s syndrome).
High worm burdens may cause abdominal pain and intestinal obstruction.
Migrating adult worms may cause symptomatic occlusion of the biliary tract or oral expulsion.
Explain why the ascaris egg is able to survive harsh conditions
Due to its mammilated shell
How may we diagnose ascaris
Microscopic identification of eggs in the stool is the most common method for diagnosing intestinal ascariasis.
Demonstration of larvae in sputum?
Describe the ways in which A lumbricoides may be transmitted
Similar to Trichuris trichiura
Highest prevalences and intensities in children (indicator of control strategy?)
Indiscriminate defecation seeds ground with eggs (remain viable for years)
Uncooked, night-soil propagated vegetables
Wind-borne dust may also carry eggs
Treat with albendazole
A. lumbricoides suum – zoonotic in man?
Which age group is most at risk for Ascariasis and has the highest worm burden
Children 0-12
What is Toxocaris canis
A
