Biology Reference
In-Depth Information
BOX 13.1
ASCARIS LUMBRICOIDES
AND ASCARIASIS
Ascariasis refers to the spectrum of disease manifestations caused by
infection with Ascaris lumbricoides. The pathology caused by infection
corresponds to the life-cycle stage and the intensity of infection. Acute
disease can arise due to larval migrations or adult worms causing
intestinal obstruction, whereas chronic disease is due to the insidious
effects of infection on nutrition and cognition and is most common
among children, due to age-related intensity patterns. The main features
of ascariasis include:
IMPACT OF
Pulmonary migration induces hypersensitivity, which can manifest as
asthma (see Chapter 2). The reaction to migration can be severe
resulting in cough, hypersecretion of mucus, and bronchiolar
inflammation, which is usually subclinical.
The intestinal phase of infection is generally asymptomatic, but heavy
infection can cause physiological abnormalities in the small intestine
resulting in malabsorption of nutrients, vitamin A and other
micronutrients, nutritional deficiency and growth failure, especially
in children.
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Moderate and heavy infection in children may also adversely affect
cognitive development.
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e
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Heavy infection can cause serious complications, the most common of
which is small bowel obstruction by a bolus of worm, leading to
gastrointestinal discomfort, vomiting, and occasionally
intussusception and death.
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Ascaris-related intestinal obstruction
most commonly occurs in the ileum of young children.
Female A. lumbricoides worms can migrate up the common bile duct
into the liver where they can cause bile duct obstruction leading to
cholangiitis or pancreatitis.
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The worms can also die, releasing
eggs. Granulomatous reactions around the dead worm can result in
liver abscess and acute upper abdominal pain, sometimes with fever
and jaundice.
Liver abscesses can be caused by female A. lumbricoides worms
migrating up the common bile duct into the liver where they die,
releasing eggs. Histologically there is a granulomatous reaction round
the dead worm with release of the eggs.
