Ascariasis

Ascariasis (roundworm infection) is the most common helminthic infection. It occurs worldwide but is most common in tropical areas with poor sanitation and in areas where farmers use human stool as fertilizer. In the United States, it's more prevalent in the South, particularly among children younger than age 12.

Causes

Ascariasis is caused by Ascaris lumbricoides, a large roundworm that resembles an earthworm. It's transmitted to humans by ingestion of soil contaminated with human stool that harbor A. lumbricoides ova. Ingestion may occur directly (by eating contaminated soil) or indirectly (by eating poorly washed raw vegetables grown in contaminated soil).

After ingestion, A.lumbricoides ova hatch and release larvae, which penetrate the intestinal wall and reach the lungs through the bloodstream. After about 10 days in pulmonary capillaries and alveoli, the larvae migrate to the bronchioles, bronchi, trachea, and epiglottis. There they are swallowed and returned to the intestine to mature into worms.

Signs and Symptoms

The following symptoms may be seen with mild infestation:

• Passing worms in stool
• coughing up worms
• loss of appetite
• fever
• Skin rash
• wheezing

More severe infestations can result in more serious signs and symptoms, including:

• Vomiting
• shortness of breath
• abdominal distention
• severe stomach or abdominal pain
• intestinal blockage
• biliary tract blockage (includes the liver and gallbladder)

Diagnostic tests 

The key to diagnosis is identifying ova in the stools, or adult worms, which may be passed rectally or by mouth.

Treatment

Anthelmintic therapy, the primary treatment, uses mebendazole or albendazole. These are contraindicated in pregnancy and in heavy infections, in which ectopic migration can occur. Pyrantel pamoate and piperazine are safe in pregnancy.

In intestinal obstruction, nasogastric (NG) suctioning controls vomiting. When suctioning can be discontinued, instill piperazine and clamp the nasogastric tube. If this is ineffective, surgery is probably needed. Endoscopic retrograde cholangiopancreatography and papillectomy may be required for helminth removal.

Prevention

Improved sanitation and hygiene in developing countries will reduce the risk in those areas. In areas where this disorder is common, routine or preventive (prophylactic) treatment with deworming medications may be advised.