Ascariasis (Ascaris lumbricoides)

                     

Ascariasis (Ascaris lumbricoides)

most prevalent human helminthiasis,

most common in children of preschool or early school age.

ETIOLOGY.

infective stage = mature larva-containing egg.

oval, has a thick shell

Eggs are passed in the feces of infected individuals

mature in 5–10 days under favorable conditions

become infective.

Each female has a life span of 1–2 yr

capable of producing 200,000 eggs/24 hr.

PATHOGENESIS.

eggs ingested by a human host à larvae released from the eggs à  penetrate the intestinal à  to the lungs via the venous circulation. à break through the pulmonary tissues into the alveolar spaces à  ascend the bronchial tree and trachea, à  reswallowed.

On their arrival in the small intestine, the larvae develop into mature adult worms.

pathogenesis of pulmonary ascariasis not known,

a hypersensitivity phenomenon may be involved.

Adult worms may cause gastrointestinal (GI) disease by obstructing the gut or biliary tree and by affecting host nutrition.

CLINICAL MANIFESTATIONS.

manifested during migration of the larvae through the lungs

may be because  of adult worms in the small intestine.

nutritional status of children with ascariasis may be affected

Pulmonary ascariasis = cough blood-stained sputum, and eosinophilia.

Löffler's-like syndrome

DD = visceral larva migrans

abdominal symptoms or signs are rare in pulmonary ascariasis.

adult worms in the small intestine

vague complaints such as abdominal pain and distention.

Intestinal obstruction = due to a mass of worms in heavily infected children

age 1–6 yr.

onset is sudden,

severe colicky abdominal pain and vomiting,

may be bile stained;

Migration of Ascaris worms into the biliary tract = acute, colicky abdominal pain, nausea, vomiting, and fever. Jaundice rare

Steatorrhea and diminished vitamin A absorption

DIAGNOSIS.

eggs =detected by direct fecal smear examination

Diagnosis of pulmonary ascariasis or GI ascariasis = on clinical symptoms and a high index of suspicion.

TREATMENT.

uncomplicated GI ascariasis is albendazole (400 mg PO as a single dose).

Alternatives

            mebendazole (100 mg bid for 3 days

            pyrantel pamoate (11 mg/kg once; maximum, 1 g) orally.

Piperazine salts cause neuromuscular paralysis of the parasite and rapid expulsion of the worms and are the treatment of choice for ascariasis complicated by intestinal or biliary obstruction.

Piperazine is administered orally in a daily dose of 50–75 mg/kg for 2 days.

hypersensitivity and neurotoxic reactions have been reported with piperazine derivatives. surgical treatment may be needed in severe obstructive cases.

PREVENTION.

mass chemotherapy -repeated at 3–6-mo intervals.

Sanitary practices = treating human feces before it is used as fertilizer

hygienic sewage disposal facilities