ASCARIS LUMBRICOIDES Flashcards
What is the common name of Ascaris Lumbricoides?
Round worm(largest intestinal)
approximately 1billion infected.
What’s the habitat for ascaris?
Adults= SMALL INTESTINES
Larvae= LUNGS
Describe the Morphology of ascaris
Flesh colored, whitish lateral line when freshly passed, large cylindrical worm!
①Male worm smaller than female: 15 - 30 cm, Tail curved ventrad
②Female worm larger than males: 20 - 40 cm, lay about 200,000 eggs per day.
* Posterior extremity of male worm is curved ventrally to form a hook
* Posterior extremity of female worm is straight and conical
③Eggs
* Fertilized eggs have an outer shell membrane which is heavily mammillated
* Unfertilized eggs often appear longer, and thinner shelled
How is ascaris lumbricoides transmitted?
Mainly through ingestion of water or food (raw vegetables or fruits in particular) or contaminated
soil with A. lumbricoides eggs
* Children playing in contaminated soil may acquire
the parasite from their hands
* Deliberate ingestion of soil or pica is a significant
risk factor for infection (children & pregnant &
lactating women)
What are the risk factors of ascaris lumbricoides transmission?
①The use of waste water for irrigation
②Overcrowding
③Poor education of mothers
④Inadequate water supply
⑤Not washing hands before eating
⑥Peak infections are seen in childhood or early adolescence
What are the hosts of ascaris?
man and pigs are definitive hosts with no intermediate hosts.
Occurs during rainy months, tropical & subtropical countries
Life Cycle of Ascaris lumbricoides;
Adult worms ①live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces
②Unfertilized eggs may be ingested but are not infective. Larvae develop to infectivity within fertile eggs after 18 days to several weeks
③depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed
④the larvae hatch
⑤invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs
⑥The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed
⑦Upon reaching the small intestine, they develop into adult worms.
Between 2 and 3 months are required from ingestion of the infective eggs to oviposition by the adult female. Adult worms can live 1 to 2 years
Pathogenesis of Ascaris lumbricoides；
Disease is called ascariasis
* Clinical manifestation caused by either migrating larvae or by
adultworm
How do adult worms contribute to Ascariasis?
light infections not serious
* Colic, anorexia, nervous, fretfulness,
protuberance of abdomen in children.
* Nutritional impairment, steatorrhoea
* shortening of villi
Ascariasis in febrile children;
In febrile children worms congregate, and cause obstruction of small bowel
How do migrating larvae contribute to Ascariasis?
First passage through liver without remarkable pathological changesSensitizing
· Later migrations causes Oesinophilic infiltration & periportal
granuloma
* Ascaris bronchospasm = Ascaris pneumonitis,
= Loeffler’s Syndrome, shifting mottling seen on lung X-ray,
dyspnea, wheezing.
· Sputum with larvae, oesinophils, CLCs
· Pulmonary Ascariasis occasionally fatal
Ectopic Ascariasis:
①Migrating males penetrate liver via billiary and pancreatic ducts, can become impacted, and cause liver abscesses obstructive jaundice
②lungs via trachea in comatose state,
③nasopharynx , exit through nares, asphyxia, anaphylaxis
④Appendix and peritoneal cavity: gangrene of the SI
⑤⑥⑦Heart, pulmonary arteries, ventricles, brain,kidney
Associated with whipworm
⑧Adult worms may rarely be
recovered from the anus, mouth, throat or nose.
What are most ascaris symptoms attributed to?
①Effects of larval migration
②Mechanical effects of adult worms
③Nutritional deficiencies due to adult worms
④Host immune response
* Intense infections are seen in children aged five to 15 years
* Infections tend to decline in adulthood
* Most infections - clinically asymptomatic
Infection due to larval migration in the lungs may cause:
*Haemorrhagic/eosinophilic pneumonia, cough
(Loeffler’s Syndrome)
* Breathing difficulties and fever
* Sputum may be blood tinged & may contain larvae (heavy infections)
* Complications caused by parasite proteins (ascarions)
that are highly allergenic – asthmatic attacks,
pulmonary infiltration and urticaria (hives)
Clinical symptoms normally manifest 5-6 days post-infection & may last for 10-12 days
Adults in the intestine may cause:
– Lactose intolerance
– Vitamin A malabsorption
– Intestinal obstruction or abdominal discomfort especially in children
– Nausea in mild cases
– Hepatic disease
– Severity of symptoms depends on number of infective
eggs ingested & history of previous infection
– Infarction & perforation of the intestines results in peritonitis
– Complications are rare
– If present in large numbers, worms can cause
– Abdominal distension and pain
– Nausea
– Vomiting
– Restless sleep
– Tooth grinding
– In adults, worms may block bile duct resulting in cholangitis,
cholecystitis, hepatic abscesses & pancreatitis
– In children, heavy infections have been associated with malnutrition & growth retardation
