Source: Centers for Disease Control and Prevention, National Center for Infectious Diseases, Division
of Parasitic Diseases
"An ascarid is a worm that lives in the small intestine... Ascarid eggs are found in the soil. Infection
occurs when a person accidentally ingests (swallows) infective ascarid eggs..."
Although infections may cause stunted growth, adult worms usually cause no acute symptoms. High
worm burdens may cause abdominal pain and intestinal obstruction. Migrating adult worms may
cause symptomatic occlusion of the biliary tract or oral expulsion. During the lung phase of larval
migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis -
More than a billion people worldwide are infected with one or more species of intestinal nematodes.
The ascariasis is one of the roundworm parasites more common seen of human being and it is
calculated that the world population's fourth part is infected. Although that the clinical pictures of this
illness courses mostly with silent form or chronic symptomatology, the massive infestation in children
can give place to serious complications that require surgical urgency attention for experts.
Every year, 60.000 deaths are attributed directly to this infection. This helmintic infection is acquired
by the ingestion of eggs; the larvae during their migration go by the lung to complete their
maturation, they ascend for the respiratory tree and then continuing go up for later to be swallowed
and arrive to the small intestine where they become adults.
Migrating larvae may transmit other organisms, causing bacterial pneumonia. Rare cases of airway
obstruction have also been reported. Other much less common presentations include lacrimal
drainage obstruction, acute interstitial nephritis, and encephalopathy.
Intestinal nematode infections affect one fourth to one third of the world's population. Of these, the
intestinal roundworm Ascaris lumbricoides is the most common. While the vast majority of these
cases are asymptomatic, infected persons may present with pulmonary or gastrointestinal complaints.
Ascariasis predominates in areas of poor sanitation and is associated with malnutrition, iron-
deficiency anemia, and impairments of growth and cognition.
Once ingested, eggs hatch, releasing small larvae that penetrate the intestinal wall. Larvae migrate to
the pulmonary bed via the portal veins, during which time they may cause pulmonary symptoms (eg,
cough, wheezing). After migrating up the respiratory tract and being swallowed, they mature,
copulate, and lay eggs in the intestines. Adult worms may live in the gut for 6-24 months, where they
can cause partial or complete bowel obstruction in large numbers, or they can migrate into the
appendix, hepatobiliary system, or pancreatic ducts.
In the United States, approximately 4 million people are believed to be infected.
The rate of complications secondary to ascariasis ranges from 11-67%, with intestinal and biliary tract
obstruction representing the most common serious sequelae. Although infection with A lumbricoides
is rarely fatal, it is responsible for an estimated 8,000-100,000 deaths annually, mainly in children
PATHOGENICITY: Helminthic infection of small intestine; pulmonary manifestations may occur; serious
complications, including bowel obstruction or obstruction of bile duct, pancreatic duct and appendix;
may be fatal
EPIDEMIOLOGY: Worldwide; commonly occurring in tropical countries; greatest in children aged 3-8
HOST RANGE: Varies with species (A. lumbricoides - humans, occasionally swine; A. suum - swine)
INFECTIOUS DOSE: Unknown
MODE OF TRANSMISSION: By ingestion of infective eggs from soil contaminated with human faeces or
from uncooked food contaminated with soil containing infective eggs; transmission of infection by
dust is also possible; fresh faeces do not contain infective eggs