Ascariasis

CASES/YEAR
400 (US); 807,000,000 (Global)
CATEGORY
Intestinal Nematodes
AGENT TYPE
Helminths
OTHER NAMES
Ascaris lumbricoides infection;
ACUITY
Subacute/Chronic
INCUBATION
2-8 weeks; 2-24 months
INITIAL SYMPTOMS
Most patients are asymptomatic. Patients may pass live worms (15 to 35 cm long and white or pink colored); [PPID, p. 3200]
PRECAUTIONS
"Not transmitted from person to person." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
Complications include nutritional disorders, bowel or bile duct obstruction, appendicitis, and pancreatitis. Infection occurs after eating soil or produce contaminated with human feces containing the eggs of this intestinal nematode. The eggs take about 2 weeks in the soil before becoming infective, so direct fecal-oral transmission does not occur. [CCDM, p. 54-5] Patients may have allergic symptoms during the pulmonary phase to include wheezing, cough, hemoptysis, chest pain, and cyanosis. Outbreaks of pneumonitis (sudden onset of wheezing, dry cough, and high fever) occur in some areas following the rainy season. [Cecil, p. 992-3] Jaundice from biliary obstruction is uncommon. [Merck Manual, p. 1669] Eosinophilic pneumonitis (Loffler's syndrome) occurs about 9-12 days after egg ingestion. [Harrison ID, p. 1131] Ascaris pneumonia is diagnosed by detecting larvae in respiratory secretions, not in the stool. "At least 40 days must elapse before the larvae responsible for pulmonary infiltrates have matured sufficiently to produce eggs detectable in the stool." Marked eosinophilia is associated with larval migration, but not with adult worms. Urticaria may occur. [Guerrant, p. 939-46] Heavy infections in children can contribute to malnutrition and growth retardation. [ID, p. 2357] Acararis lumbricoides can cause hepatic abscesses and hepatomegaly. [Guerrant, p. 1260-2, 1538] Many patients are asymptomatic or have mild abdominal pain or nausea. The larvae reach the lung 4 days after ingestion. Unless reinfection occurs, Ascariasis lasts only 1-2 years, the lifespan of the worms. In tropical areas, ascariasis is a common cause of surgery for "acute abdomen." In a series of cases of biliary and pancreatic ascariasis, patients had biliary colic (46%), acute cholangitis (24%), cholecystitis (13%), acute pancreatitis (6%), and liver abscesses (1%). [PPID, p. 3200-2]
DIAGNOSTIC
Identify eggs (light microscopy) or adult worms; Larvae in sputum or gastric washings proves pulmonary involvement; Visualize intestinal worms by x-ray or sonography; [CCDM] Eggs produced in large numbers: easy to find in fecal exam; [PPID]
SCOPE
Most common in wet tropical regions where prevalence of infection often exceeds 50%; [CCDM]
SIGNS & SYMPTOMS
  • >fever
  • G abdominal mass
  • G abdominal pain
  • G constipation
  • G diarrhea
  • G hepatomegaly
  • G jaundice
  • G liver function test, abnormal
  • G nausea, vomiting
  • H eosinophilia
  • R chest pain
  • R cough
  • R dyspnea
  • R hemoptysis
  • R wheezing
  • S urticaria
  • X lung infiltrates
  • *bowel obstruction
  • *erythema nodosum
  • *pancreatitis
  • *pneumonia
  • *pneumonitis
  • *weight loss
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
Ingestion
SOURCE
Fecally Contaminated Soil, Soil or Dust (Ingesting or Inhaling), Eating Contaminated Food, Eating Contaminated Produce
RESERVOIR
Human
RISK FACTORS
  • Eat soil containing infective eggs
  • Ingest infectious agents in food/water
TREATMENT
Albendazole 400 mg X 1 dose; Pulmonary ascariasis is self-limited. Some cases of biliary obstruction can be treated with endoscopic retrograde cholangiopancreatogram (ERCP). [Cecil, p. 2129]
REFERENCES FOR CASES/YEAR
1. (US) Prevalent in SE US; [Gorbach, p. 346] Now rare in the US, although about 4 million people were infected several decades ago, mainly in the rural Southeast. [ID, p. 2357] Global cases/yr is about 800 million; 4 million is 1/200 of 800 million; Now rare in US; Guesstimate of 400 cases/year;
2. (Global) 1.5 billion (Ascariasis, Trichuriasis, and hookworm infections (N. americanus & A. duodenale); [Fact sheets from WHO 2013] Global prevalence 807 million; [Harrison ID, p. 1132t]