Ascariasis
Parasite cycle
Understanding the life cycle of'Ascaris lumbricoides is essential to understand the diversity of clinical manifestations and the appropriate therapeutic windows. The cycle comprises a migratory larval phase and an intestinal adult phase.
| Step | Description | Delay |
|---|---|---|
| Ingestion of eggs | Embryonated eggs ingested via food, water or hands contaminated with faecal matter | Day 0 |
| Intestinal hatching | L2 larvae hatch in the small intestine and cross the intestinal wall | Days 1 to 3 |
| Larval migration | The larvae reach the liver via the portal vein, then the lungs via the bloodstream. | Weeks 1 to 2 |
| Lung phase | Larvae ascend the respiratory tract, are deglutinated and return to the small intestine | Weeks 2 to 3 |
| Intestinal maturation | Larvae develop into adult male and female worms in the small intestine | Weeks 4 to 8 |
| Ponte | The female lays up to 200,000 eggs per day, excreted in the feces. | From 2 months |
| Adult worm lifespan | 12 to 18 months in the absence of treatment | Variable duration |
Clinical manifestations
The symptoms of ascariasis vary according to the parasite load and the phase of the cycle. There is a larval invasion phase, often respiratory, and an intestinal state phase, the expression of which depends closely on the number of worms present.
| Phase | Events | Mechanism |
|---|---|---|
| Pulmonary larval phase (Löffler syndrome) | Dry or productive cough, dyspnea, sibilance, moderate fever, transient pulmonary infiltrates | Larvae migration into pulmonary alveoli, eosinophilic reaction |
| Light intestinal phase | Often asymptomatic or vague abdominal pain, nausea, digestive discomfort | Low number of adult worms, minimal mucosal irritation |
| Moderate to severe intestinal phase | Crampy abdominal pain, abdominal distension, diarrhea, vomiting, anorexia | Heavy infestation, nutritional competition, mechanical irritation |
| Nutritional impairment | Protein-energy malnutrition, stunted growth, anemia, vitamin A deficiency | Subtraction of nutrients by parasites, intestinal malabsorption |
| Obstructive complications | Intestinal obstruction, cholangitis, pancreatitis, appendicitis | Mass of worms obstructing the intestinal lumen or migrating into the bile ducts |
Intestinal obstruction due to ascariasis is a surgical emergency. If you experience severe abdominal pain, fecal vomiting, cessation of feces and gas, or a rigid abdomen, go immediately to the emergency room or call 911.
Risk factors and exposure contexts
- Prolonged stay or residence in a tropical or subtropical region with low sanitation levels
- Consumption of fruit, vegetables or water potentially contaminated with faecal matter
- Contact with contaminated soil, especially for children playing on the ground
- International adoption of children from endemic areas
- Use of man-made organic fertilizers (farming practice in some regions)
- Poor socio-economic conditions with limited access to drinking water and sanitary facilities
- Immunosuppression may favour more severe infestation
Diagnostic approach
Diagnosis of ascariasis is based primarily on the detection of parasite eggs in the stool. Other tests may be useful, depending on the clinical context and the stage of the disease.
- Parasitological stool examination (PSE): identification of characteristic eggs of'Ascaris lumbricoides, repeat on three samples on different days to increase sensitivity
- Blood count: frank eosinophilia (hypereosinophilia) in larval migratory phase
- Parasite serology: little used in current practice, useful in atypical cases
- Abdominal X-ray or ultrasound: possible visualization of a mass of worms in the event of massive infestation
- Chest X-ray: labile pulmonary infiltrates and eosinophilia in Löffler phase
- Upper GI endoscopy or colonoscopy: direct visualization of worms in cases of atypical migration
- Nutritional assessment in children: evaluation of associated deficiencies (iron, vitamin A, protein)
Anti-parasite treatment
Treatment of ascariasis is based on the administration of anthelmintic agents effective against adult intestinal worms. Management of mechanical complications may require endoscopic or surgical intervention.
| Drug | Usual dosage | Remarks |
|---|---|---|
| Albendazole | 400 mg single oral dose | First-line treatment, efficacy greater than 95 %; avoid in the first trimester of pregnancy |
| Mebendazole | 100 mg twice a day for 3 days, or 500 mg as a single dose | First-line alternative, good general tolerance |
| Ivermectin | 150 to 200 µg/kg single dose | Useful alternative in case of co-infestation with other nematodes |
| Pyrantel pamoate | 11 mg/kg as a single dose (maximum 1 g) | Can be used during pregnancy after the first trimester |
Prevention and hygiene measures
The prevention of ascariasis relies on rigorous hygiene measures and improved sanitary conditions. In endemic areas, public health authorities set up collective deworming programs.
- Hand washing with soap and water before meals and after contact with soil or faeces
- Consumption of drinking or previously boiled water during stays in endemic areas
- Careful washing of fruit and vegetables, and proper cooking of high-risk foods
- Wear shoes to avoid direct contact with potentially contaminated soil
- Avoid children's contact with soil contaminated by human faeces
- Consult a doctor before and after any trip to a tropical zone for an appropriate parasitological check-up.
Ascariasis in children: special features
Children between the ages of 2 and 10 represent the most vulnerable population to ascariasis, due to their high-risk behaviors (playing in the soil, less rigorous hand hygiene) and greater susceptibility to nutritional complications. Chronic infestation can compromise a child's physical and cognitive development. School deworming programs in endemic areas are specifically designed to reduce the parasite load in this age group.
Consult at Clinique Omicron
Have you just returned from a trip to a tropical zone, are you experiencing unexplained abdominal pain, a persistent cough accompanied by eosinophilia, or would you like a parasitological check-up on your return from a trip? Clinique Omicron's physicians, available at our points of service in Quebec, can prescribe and interpret a parasitological stool examination, recommend the appropriate antiparasitic treatment and provide post-treatment follow-up. A post-travel check-up is available at one of our points of service on the South Shore or at our branches in Quebec, with or without appointment, depending on availability.
The content of this page is provided for informational purposes only and is not intended to replace the advice of a qualified healthcare professional. Consult a physician for any symptoms, questions or decisions you may have regarding your health.
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