Ascariasis (roundworm infection)

Notification requirement for ascariasis

Notification is not required.

Primary school and children’s services centre exclusion for ascariasis

If diarrhoea is present, exclude until there has not been a loose bowel motion for 24 hours.

Infectious agent of ascariasis

The infective agents are Ascaris lumbricoides, a large intestinal roundworm (the female can be up to 30 cm long), and A. suum, a similar parasite primarily affecting pigs and occasionally humans. Infection occurs worldwide and is most common in tropical and subtropical areas where sanitation and hygiene are poor.

Ascaris lives in the intestine, and its eggs are passed in the faeces of infected people. If the infected person defecates outside or if the faeces of an infected person are used as fertiliser, the eggs can be deposited in the soil.

Depending on environmental conditions, the eggs can mature into an infective form after 18 days, but may take several weeks to do so. Under favourable conditions, eggs can remain viable for many years.

Mature (infective) eggs can be ingested from hands that have come into contact with contaminated soil, or can be consumed with vegetables or fruits that have not been properly washed, peeled and cooked.

Once ingested, the mature eggs hatch into larvae, invade the intestinal mucosa and are carried via the portal, then systemic, circulation to the lungs.

The larvae mature in the lungs for 10–14 days, penetrate the alveolar walls, ascend the bronchial tree to the throat and are swallowed. When they reach the intestine they develop into adult worms.

The life cycle can take 2–3 months, and adult worms can live for 1–2 years. A female may produce approximately 200,000 eggs per day. The eggs are then passed in the faeces of the infected person.

Identification of ascariasis

Clinical features

Many people have few or no symptoms. Often the first symptom is live worms being passed in the stool or occasionally from the mouth, anus or nose.

In mild or moderate ascariasis, the intestinal infestation can cause vague abdominal pain, nausea, vomiting, diarrhoea or bloody stools.

In heavy intestinal infestations, patients may experience severe abdominal pain, fatigue, vomiting, weight loss and a worm or worms in vomit or stool.

Heavy infestation may aggravate nutritional deficiencies and impair growth in children or cause intestinal blockage by a bolus of worms. Obstruction of the bile duct, pancreatic duct or appendix by one or more adult worms can occur.

Patients with pulmonary conditions caused by larval migration are characterised by wheezing, cough, fever, eosinophilia and pulmonary infiltration.

Diagnosis

Diagnosis can be made by the identification of eggs or the presence of adult worms passed in faeces or from the anus, mouth or nose.

Intestinal worms can be seen using radiological or sonographic techniques or more rarely in sputum or gastric washings.

Incubation period of Ascaris

The life cycle usually takes 4–8 weeks.

Public health significance and occurrence of ascariasis

Ascaris infects an estimated 1 billion people around the world. This is more than any other parasitic worm infection.

Roundworm infections are common in temperate or tropical regions. In communities where poor sanitary conditions exist, prevalence can exceed 50 per cent of the population.

Ascariasis acquired in Australia is rare.

The prevalence and intensity of infection are usually highest in children aged 3–8 years.

Reservoir of Ascaris

Ascaris eggs in soil or infected humans act as reservoirs.

Mode of transmission of Ascaris

Transmission occurs when eggs are swallowed from soil contaminated with human faeces or consumed with produce contaminated with soil containing infective eggs.

Transmission does not occur from direct person-to-person contact or from fresh faeces.

Period of communicability of ascariasis

Ascariasis is communicable as long as the mature fertilised female worm lives in the intestine. The usual lifespan is 12 months, but it has been reported to be as long as 24 months.

Susceptibility and resistance to ascariasis

All people are susceptible, and infection does not confer immunity.

Control measures for ascariasis

Preventive measures

Avoid contact with soil that may be contaminated with human faeces and avoid using manure fertiliser potentially containing human faeces.

Promote effective hand hygiene, particularly before preparing or consuming food or feeding children.

Wash, peel or cook all raw vegetables and fruits before eating.

Teach children the importance of hand hygiene to prevent infection.

Control of case

The usual treatment is albendazole, mebendazole or pyrantel. Ivermectin is also effective. Consult the current version of Therapeutic guidelines: gastrointestinal.

Nutritional supplements may be necessary in children.

When worms obstruct the pancreatic duct or migrate up the biliary tree, surgical or endoscopic removal of the worms may be necessary.

Control of contacts

Consider faecal screening of household members to determine whether they also require treatment.

Control of environment

Environmental sources of infection should be investigated.

Outbreak measures for ascariasis

Not applicable.