Ascariasis
Ascariasis is a type of roundworm infection.
Ascaris is parasitic worm infection causes ascariasis in humans. it is the most common parasitic worm infection in humans, type of roundworm of genus ascaris.
These parasitic worm use body as a host to mature from larvae or eggs to adult worms.
Ascaris lumbricoides parasite is roundworm causes ascariasis in human.
Ascariasis cause in human due to ingesting worm eggs that infects human small intestine and getting nutrients from human’s intestinal tract.
Etiology
1. Contaminated hands or fingers put in the mouth
2. By eating contaminated vegetables or fruits that not carefully peeled, washed, or cooked.
3. Human contract ascariasis by eating or drinking contaminated food or water.
4. Human feces can cause contamination if an infected person defecates near a farming field or water source,
5. Using contaminated feces as fertilizer for crops.
Symptoms
1. Abdominal discomfort or pain
2. Slow growth in children
3. Loss of appetite
4. Worms visible in stool
5. Vomiting
6. worms visible in stool
7. Diarrhea
8. Nausea
9. Malnutrition
10. Intestinal obstruction.
In advanced infestations, the worms can travel to the lungs.
Symptoms
1. Fever
2. Discomfort in chest
3. Bloody mucus
4. Coughing
Pathogenesis
Larvae lodge in the alveolar capillaries, penetrate alveolar walls, and ascend the bronchial tree into the oropharynx.
They are swallowed and return to the small bowel, where they develop into adult worms, which mate and release eggs into the stool.
Symptomatic ascariasis; two types
1. Intestinal Ascariasis
2. Pulmonary Ascariasis
Life Cycle of Ascariasis
Stage I; Eggs in faeces
If an individua ingests the eggs of Ascaris lumbricoides.
Sexually mature female produces as many as 200,000 eggs per day, which are shed along with faeces in unembryonated form. They are non infective.
Stage II; Development in soil
Embryonation occurs in soil as optimum temperature of 20-25C with sufficient moisture and O2
Infective larva develops within egg in about 3-6 weeks.
Stage III; Human infection and liberation of larvae
Human get infection with ingestion of embryonated egg contaminated food and water.
After infective eggs are swallowed, larvae hatch and invade the intestinal mucosa.
Within embryonated state inside egg, first stage larvae develops into second stage larvae. This second stage larvae is known as Rhabtitiform larvae.
Second stage larve is stimulated to hatch out by the presence of alkaline pH in small intestine and solubilization of its outer layer by bile.
Worm invade the intestinal mucosa, and are carried via the portal, then systemic circulation to the lungs and larvae mature further in the lungs and penetrate.
Stage IV; Migration of larvae through lungs
Hatched out larvae penetrates the intestinal wall and carried to liver through portal circulation
It then travels via blood to heart and to lungs by pulmonary circulation within 4-7 days of infection.
The larvae in lungs develop twice, enlarge and breaks into alveoli.
Stage V; Re-entry to stomach and small intestine
From alveoli, the Larvae then pass up through bronchi and into trachea and then swallowed.
The larvae passes down the oesophagus to the stomach and reached into small intestine once again.
Adult worms live in the lumen of the small intestine.
Small intestine is the normal habitat of Ascaris and it colonises here.
Within intestine parasite molds twice and mature into adult worm.
Sexual maturation occurs with 6-10 weeks and the mature female discharges its eggs in intestinal lumen and excreted along with faeces, continuing the life cycle.
The life span of parasite is 12-18 months.
Laboratory Investigation
1. Specimen; Stool, sputum
2. X-ray
3. Ultrasonography and CT scan
4. Serodiagnosis
a. Indirect haemagglutination test
b. Immuno-fluorescence assay
5. Blood count; shown peripheral eosinophilia
Prevention
1. Avoid to put contaminated hand in mouth
2. Wash thoroughly vegetables
3. Waging hand before food handling
4. Filter and boil water before drinking
5. Avoid playing children with contaminated soil
6. Properly cook the raw vegetables
Treatment and Prophylaxis
Mebendazole (100mg)
Albendazole (400mg)
Complication
Once inside the lungs, larvae pass into air sacs (alveoli) in the lungs, move up the respiratory tract and into the throat, and are swallowed.
