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==Pathophysiology==
==Pathophysiology==
===Life cycle===
===Life cycle===
[[Image:Ascariasis LifeCycle - CDC Division of Parasitic Diseases.gif|thumb|left|260px|Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4), the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs . The larvae mature further in the lungs (6) (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). 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.]]First appearance of eggs in stools is 60-70 days. In larval ascariasis, symptoms occur 4-16 days after infection.  The final symptoms are gastrointestinal discomfort, colic and vomiting, fever; observation of live worms in stools. Some patients may have pulmonary symptoms or neurological disorders during migration of the larvae. However there are generally few or no symptoms. A bolus of worms may obstruct the intestine; migrating larvae may cause pneumonitis and [[eosinophilia]].
[[Image:Ascariasis LifeCycle - CDC Division of Parasitic Diseases.gif|thumb|left|260px|Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4), the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs . The larvae mature further in the lungs (6) (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). 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.]]
===Source===
The source of transmission is from soil and vegetation on which fecal matter containing eggs has been deposited. Ingestion of infective eggs from soil contaminated with human feces or transmission and contaminated vegetables and water is the primary route of infection. Intimate contact with pets which have been in contact with contaminated soil may result in infection, while pets which are infested themselves by a different type of roundworm can cause infection with that type of worm (Toxocara canis, etc) as occasionally occurs with groomers.


Transmission also comes through municipal recycling of wastewater into crop fields. This is quite common in emerging industrial economies, and poses serious risks for not only local crop sales but also exports of contaminated vegetables. A 1986 outbreak of ascariasis in Italy was traced to irresponsible wastewater recycling used to grow Balkan vegetable exports.
{| align="center" class="wikitable" border="2" cellspacing="0" cellpadding="5"
 
Transmission from human to human by direct contact is impossible.[http://www.cdc.gov/ncidod/dpd/parasites/ascaris/factsht_ascaris.htm#contagious]
===Animal models for Ascaris infestation===
 
There are two animal models for studying Ascaris infection:
* Mouse-''Ascaris suum'' test model. (Howes HL Jr. J Parasitol. 1971 Jun; 57(3): 487-93.)
* ''Ascaris suum'' in experimentally infected pigs. (Lichtensteiger CA et al; 1999)
 
===Trivia===
*Ascariasis may result in allergies to shrimp and dustmites due to the shared [[antigen]], [[tropomyosin]].
*Ascaris have an aversion to some general anesthetics and may exit the body, sometimes through the mouth.[http://arpa.allenpress.com/arpaonline/?request=get-document&doi=10.1043%2F0003-9985(2000)124%3C0174:AL%3E2.0.CO%3B2]
 
----
 
{| class="wikitable" border="2" cellpadding="5" cellspacing="0" align="center"
|-
|-
! '''Genus and Species'''
! '''Genus and Species'''
! '''Ascaris lumbricoides'''
! '''Ascaris lumbricoides'''
|-
|-
|width="200pt" align="center"| '''Common Name'''  
| width="200" align="center" | '''Common Name'''  
|width="400pt" align="center"| Giant Intestinal Roundworm
| width="400" align="center" | Giant Intestinal Roundworm
|-
|-
|width="200pt" align="center"| '''Etiologic Agent of:'''  
| width="200" align="center" | '''Etiologic Agent of:'''  
|width="400pt" align="center"| Ascariasis
| width="400" align="center" | Ascariasis
|-
|-
|width="200pt" align="center"| '''Infective stage'''  
| width="200" align="center" | '''Infective stage'''  
|width="400pt" align="center"| Embryonated Egg
| width="400" align="center" | Embryonated Egg
|-
|-
|width="200pt" align="center"| '''Definitive Host'''  
| width="200" align="center" | '''Definitive Host'''  
|width="400pt" align="center"| Man
| width="400" align="center" | Man
|-
|-
|width="200pt" align="center"| '''Portal of Entry'''  
| width="200" align="center" | '''Portal of Entry'''  
|width="400pt" align="center"| Mouth
| width="400" align="center" | Mouth
|-
|-
|width="200pt" align="center"| '''Mode of Transmission'''  
| width="200" align="center" | '''Mode of Transmission'''  
|width="400pt" align="center"| Ingestion of Embryonated egg through contaminated food or water
| width="400" align="center" | Ingestion of Embryonated egg through contaminated food or water
|-
|-
|width="200pt" align="center"| '''Habitat'''
| width="200" align="center" | '''Habitat'''
|width="400pt" align="center"| Small Intestine
| width="400" align="center" | Small Intestine
|-
|-
|width="200pt" align="center"| '''Pathogenic Stage'''  
| width="200" align="center" | '''Pathogenic Stage'''  
|width="400pt" align="center"| Adult Larva
| width="400" align="center" | Adult Larva
|-
|-
|width="200pt" align="center"| '''Mode of Attachment'''  
| width="200" align="center" | '''Mode of Attachment'''  
|width="400pt" align="center"| Retention in the mucosal folds using pressure
| width="400" align="center" | Retention in the mucosal folds using pressure
|-
|-
|width="200pt" align="center"| '''Mode of Nutrition'''  
| width="200" align="center" | '''Mode of Nutrition'''  
|width="400pt" align="center"| Feeding of [[Chyme]]
| width="400" align="center" | Feeding of [[Chyme]]
|-
|-
|width="200pt" align="center"| '''Pathogenesis'''  
| width="200" align="center" | '''Pathogenesis'''  
|width="400pt" align="center"| Larva – pneumonitis, Loeffler’s syndrome;
| width="400" align="center" | Larva – pneumonitis, Loeffler’s syndrome;
Adult – Obstruction, Liver abscess, [[Appendicitis]]. With Blood-Lung Phase along with Hookworms and Strongyloides stercoralis.
Adult – Obstruction, Liver abscess, [[Appendicitis]]. With Blood-Lung Phase along with Hookworms and Strongyloides stercoralis.
|-
|-
|width="200pt" align="center"| '''Laboratory diagnosis'''  
| width="200" align="center" | '''Laboratory diagnosis'''  
|width="400pt" align="center"| Concentration methods and Direct Fecal Smear: Kato-Katz
| width="400" align="center" | Concentration methods and Direct Fecal Smear: Kato-Katz
|-
|-
|width="200pt" align="center"| '''Treatment'''  
| width="200" align="center" | '''Treatment'''  
|width="400pt" align="center"| [[Albendazole]], [[Mebendazole]], or Pyrantel Pamoate
| width="400" align="center" | [[Albendazole]], [[Mebendazole]], or Pyrantel Pamoate
|-
|-
|width="200pt" align="center"| '''Diagnostic Feature - Adult'''  
| width="200" align="center" | '''Diagnostic Feature - Adult'''  
|width="400pt" align="center"| Female - prominent genital girdle
| width="400" align="center" | Female - prominent genital girdle
|-
|-
|width="200pt" align="center"| '''Diagnostic Feature - Egg'''  
| width="200" align="center" | '''Diagnostic Feature - Egg'''  
|width="400pt" align="center"| Coarse mammilated albuminous coating
| width="400" align="center" | Coarse mammilated albuminous coating
|-
|-
|}  
|}  


==References==
==References==

Revision as of 20:41, 17 February 2017

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Imtiaz Ahmed Wani, M.B.B.S

Overview

Pathophysiology

Life cycle

Adult worms (1) live in the lumen of the small intestine. A female may produce approximately 200,000 eggs per day, which are passed with the feces (2). Unfertilized eggs may be ingested but are not infective. Fertile eggs embryonate and become infective after 18 days to several weeks (3), depending on the environmental conditions (optimum: moist, warm, shaded soil). After infective eggs are swallowed (4), the larvae hatch (5), invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs . The larvae mature further in the lungs (6) (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed (7). Upon reaching the small intestine, they develop into adult worms (8). 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.
Genus and Species Ascaris lumbricoides
Common Name Giant Intestinal Roundworm
Etiologic Agent of: Ascariasis
Infective stage Embryonated Egg
Definitive Host Man
Portal of Entry Mouth
Mode of Transmission Ingestion of Embryonated egg through contaminated food or water
Habitat Small Intestine
Pathogenic Stage Adult Larva
Mode of Attachment Retention in the mucosal folds using pressure
Mode of Nutrition Feeding of Chyme
Pathogenesis Larva – pneumonitis, Loeffler’s syndrome;

Adult – Obstruction, Liver abscess, Appendicitis. With Blood-Lung Phase along with Hookworms and Strongyloides stercoralis.

Laboratory diagnosis Concentration methods and Direct Fecal Smear: Kato-Katz
Treatment Albendazole, Mebendazole, or Pyrantel Pamoate
Diagnostic Feature - Adult Female - prominent genital girdle
Diagnostic Feature - Egg Coarse mammilated albuminous coating

References


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