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The estimations of the number of eggs in a gravid female pinworm ranges from about 11,000 [12] to 16,000. [18] The egg-laying process begins approximately five weeks after initial ingestion of pinworm eggs by the human host. [12] The gravid female pinworms migrate through the colon towards the rectum at a rate of 12 to 14 centimetres per hour. [12]
The adult male is considerably smaller, measuring 2 to 5 mm long and 0.2 mm thick, and has a curved posterior end. [18] The eggs are translucent [18] and have a surface that adheres to objects. [19] The eggs measure 50 to 60 μm by 20 to 30 μm, and have a thick shell flattened on one side. [18]
The entire process from skin penetration to adult development takes about 5–9 weeks. The female adult worms release eggs (N. americanus about 9,000–10,000 eggs/day and A. duodenale 25,000–30,000 eggs/day), which are passed in the feces of the human host. These eggs hatch in the environment within several days and the cycle starts anew.
Colonoscopy is a useful diagnostic tool, especially in patients infected with only a few male worms and with no eggs presenting in the stool sample. [19] Trichuriasis can be diagnosed when T. trichiura eggs are detected in stool examination. Eggs will appear barrel-shaped and unembryonated, having bipolar plugs and a smooth shell. [20]
Eggs are deposited from human feces to soil where, after two to three weeks, they become embryonated and enter the "infective" stage. These embryonated infective eggs are ingested by hand-mouth or through fomites and hatch in the human small intestine, exploiting the intestinal microflora as a stimulus to hatching. [4]
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Major groups of parasites include protozoans (organisms having only one cell) and parasitic worms (helminths). Of these, protozoans, including cryptosporidium, microsporidia, and isospora, are most common in HIV-infected persons. Each of these parasites can infect the digestive tract, and sometimes two or more can cause infection at the same time.
A 64-year-old Australian woman is the first documented human to be infected with a type of parasite normally found in carpet pythons. Doctors extracted a 3.1-inch living roundworm from her brain ...