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Ascaris lumbricoides (large intestinal roundworm)

Diagnostic Form:

The diagnostic form is the egg found in the feces of the host. There are generally two types of eggs that can be seen, corticated and de-corticated. The de-corticated form has a relatively smooth shell while the corticated has a very rough and bumpy shell. The eggs generally take up the lugols stain heavily and thus are generally dark in color.

 

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On occassion the adult worms will migrate outward from the host. In these cases the worms may travel up the espohagus and migrate out the host's mouth and or nose.

 

shell operculum knob interior ascaris_adult_worm

Geographic Prevalence:

Generally this parasite has a worldwide distribution, however it is most prevalent in warm moist areas.

 

Disease And Clinical Symptoms:

Ascariasis. Clinical symptoms include cough (Loffler syndrome), dyspnea, fever, and wheezing due to larval migration through the lungs. The examination of sputum may in many cases show an eosinophilia and Charco-Leyden crystals. A peripheral eosinophilia may also be induced.The adult worms in heavy infections can cause obstruction of the small bowel due to a worm bolus. In such cases it may be necessary for the surgical removal of the bolus to prevent medical complications.

It is not unusall for adult worms to migrate up the esophagus into the mouth and/or through the nose.

The author cites a case where a young female, who had recently returned from a one month vacation in Portugal, brought to the Microbiology Laboratory a covered jar with what she described as worms that had been coughed up and/or were pulled from her nose. The jar was half full of Ascaris worms!

 

Location In The Host:

Lumen of the small intestine predominantly but also found in the liver, appendix, pancreas, lungs (to cause Loffler's syndrome). Most live for up to 12 months but there are cases of them living for up to 2 years.

 

Primary Vector:

None. Humans are the resevoir.

 

Life Cycle:

 

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Test Recommended For Detection/Diagnosis:

The recommended test for the detection/diagnosis of Ascaris infections in the ova and parasite examination.

On occassion a patient will bring in a worm that may have migrated out of the host. These worms can eaily be identified and used to make a definitive diagnosis. The worms are cylindrical and elongated, tapered at both ends. The adult male worm is 12 to 31 cm in length and 2 to 4 mm in diameter. The adult female worm is 20 to 35 cm in length and 3 to 6 mm in diameter.

 

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