Ascaris

Ascaris
Adult female
Scientific classification
Kingdom:	Animalia
Phylum:	Nematoda
Class:	Secernentea
Order:	Ascaridida
Family:	Ascarididae
Genus:	Ascaris Linnaeus, 1758
Species
Ascaris lumbricoides Ascaris suum

Ascaris is a genus of parasitic nematode worms known as the "giant intestinal roundworms". One species, A. suum, typically infects pigs, while another, A. lumbricoides, affects human populations, typically in sub-tropical and tropical areas with poor sanitation. A. lumbricoides is the largest intestinal roundworm and is the most common helminth infection of humans worldwide, an infection known as ascariasis. Infestation can cause morbidity, and sometimes death, by compromising nutritional status, affecting cognitive processes, inducing tissue reactions, such as granuloma, and provoking intestinal obstruction or rectal prolapse.

Morphology

• Adult: cylindrical shape, creamy white or pinkish in color.
• Male: average 15–31 cm and is more slender than female.
• Female: average 20–35 cm in length..

Symptoms

• Bloody sputum
• Cough
• Low-grade fever
• Vomiting worms
• Passing of worm in stool
• Gallstone formation
• Liver abscesses
• Pancreatitis
• Pulmonary eosinophilia

Examination

• Abdominal X-ray
• Complete blood count
• Stool ova and parasite exam

Pathology

Lung phase

A.lumbricoides is known as Ascaris pneumonitis. In the lung it causes hemorrhage, inflammation, bacterial infection. It also causes allergy in areas with seasonal transmission. Typically occurs at 6–15 days after initial exposure.

Intestinal phase

The intestinal phase causes malnourishment, intestinal blockage, verminous intoxication. A.lumbricoides will move around in the body in response to chemotherapy or fever. Typically occurs at 6 to 8 weeks after initial exposure.

Management

Early diagnosis can be performed by examination of stool for the worm eggs. The spread or infection of A.lumbricoides can be controlled by proper disposal of faeces and proper washing of food. Control of helminthiasis is based on drug treatment, improved sanitation and health education.

Defense Mechanism

As part of the parasite defense strategy, Ascaris roundworms secrete a series of inhibitors to target digestive and immune-related host proteases, which include pepsin, trypsin, chymotrypsin/elastase, cathepsins, and metallocarboxypeptidases (MCPs). Ascaris inhibits MCPs by releasing a enzyme known as Ascaris carboxypeptidase inhibitor (ACI). This enzyme binds to the active site of MCP and blocks the cleavage of its own proteins by the host MCP (Sanglas et al., 2008)

Treatment

Infections with A.lumbricoides are easily treated with a number of anthelmintic drugs:

• pyrantel pamoate given as a single dose of 10 mg/kg
• levamisole given as a single dose of 2.5 mg/kg
• mebendazole given as a single dose of 500 mg
• albendazole given as a single dose of 400 mg.sup

The drugs' main target is the absorbing cells of the worm. The drugs prevent the worm from absorbing sugar in the intestine which is essential for its survival. This process leads to depletion of energy in worm and its eventual death within few days. The dead worm is then excreted from the gut in the stool. Albendazole is not well absorbed by the intestines and a high fat food or meal should be consumed with each dose.

Many parasitic disease specialists are seeing increased initial incidence and recurrence of roundworm in the U.S. and are thereby increasingly recommending follow up courses of medication to treat internal eggs which have not yet hatched, in addition to the initial treatment period as above. This consists of sporadic treatment with albendazole or similar for a period of three days each month for up to five months after the initial treatment period.

More severe cases, blockage of intestine or pancreatic ducts require surgical removal of worms.

Some, including parasitologist Dr. Hulda Clark have advocaated a diet high in Jalepeno peppers, citing the low incidence of Ascaris infection in Mexicanos.

See ascariasis for more information.

References

• Sanglas, Laura; Aviles, Francesc X.; Huber, Robert; Gomis-Ruth, F. Xavior; Arolas, Joan L. 2008. Mammalian metallopeptidase inhibition at the defense barrier of Ascaris parasite. University of Barcelona, Spain.
• http://health.dir.groups.yahoo.com/group/DrClark/message/19422?var=1

• 

  Esophagus of an Ascaris worm.

• 

  Ascaris Cross Section 40X

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  Ascaris Cross Section 40X

• 

  antivaisa Cross Section 400X

See also

• List of parasites (human)