Ascaris Lumbricoides

University:
Franklin University
Course:
BIO-201 | Introductory Biology I
Academic year:

2021
Views:

333

Pages:

29
Author:

LunarLuminary

1- Ascaris lumbricoides 1- Ascaris lumbricoides  Soil-Transmitted Helminths (STH) or Geohelminths  Ascariasis or Ascariosis  Roundworm infection  Dedan (Arabic) Geographic distribution/epidemiology:  Cosmopolitan  Worldwide at least 1.5 billion humans are infected  One of the most common worms infecting humans (after Enterobius vemicularis) Location in host: • Adults are normally found in the lumen of the small intestine but do not attach to the mucosa • Parasitize mainly in the small intestine of humans, monkeys and apparently also in bears Biology, morphology:  Adult worms:  Adult yellowish-white  Length (males: 10–30 cm; females: 22–52 cm)  They are characterized by their anterior (mouth region) three-lipped head capsule with tiny teeth at the borders  Egg (Ovum):  The females can lay up to 200,000 eggs a day for a rather long period (up to 1 year, only rarely longer)  Eggs are: • Yellowish-brown, sculptured surface, broadly oval  Fertilized egg size: 45–70 μm × 35–50 μm Infection of humans: • The ova are unsegmented (unembryonated) when passed in the faeces • In outside of the body under influence of oxygen the formation of the larva 1 (L1) inside the ova is started, which moults into the infectious larva 2 (L2) (Rabditiform larva) • The infection of humans occurs by oral uptake of larva-containing eggs (L2 or rabditiform larva inside egg)  Fertile unembryonated egg  Infertile egg  Second-stage infective larva (L2) in egg after at least 10–15 days’ in soil Life cycle  The infection of humans occurs by oral uptake of larva-containing eggs (L2 or rabditiform larva inside egg) 1) 2) 3) Inside the intestine, the larva 2 is set free from the egg shell Enters the intestinal wall Reaches within blood vessels the liver, where another moult leads to the formation of larva 3 (the wandering stage) 4) L3 reach after heart passage the lungs (L4 in Lungs), where they stay for about 14 days 5) Then they migrate via trachea and esophagus into the small intestine, where they reach after two more moults within 45–60 days fertility. 6) The females start copulation with males and lay eggs for about 1 year. This seems short; however, they produce during this period about 60 million eggs.  In Ascaris: larva has lung migration  The infection of humans occurs by oral uptake of larva-containing eggs (L2 or rabditiform larva inside egg) Symptoms of the disease (Ascariasis):  This worm infection may remain harmless, but also introduce severe diseases or even death  In general, the following symptoms may occur: A) During passage of the lung (Larva):  Eosinophilic lung infiltrations (eventually visible during Xray examination), fever and finally pneumonia (Loeffler’s syndrome = pneumonitis with cough, dyspnoea, substernal pain, fever and sometimes bloodstained sputum) A) Intestinal phase (Adult worms):  The usual symptoms of heavy infections are digestive disorders, nausea, vomiting and colic and, in children, restless sleep and tooth grinding (restlessness and insomnia)  Intestinal obstruction is a serious complication of Ascaris infection (X-rays examination), which usually occurs in children, often as young as 2  Ectopic migration sites (moving adult worms from intestine to other organs):  the abdominal cavity and infrequently worms pass out through various orifices (mouth, nose, lachrymal duct, urethra, vagina) Homework Assignment: What is the cause of ectopic migration in ascaris? Diagnosis: Clinical:  Pneumonitis caused by the migrating larvae is often not diagnosed, but the accompanying high eosinophilia is suggestive  The adult worms with X-rays or computer assisted tomography (CT) scan Parasitological:  Eggs in the faeces (Microscopic examination) Immunodiagnosis:  Non-specific Prophylaxis (Prevention and control):  Washing of salad and plants before eating  Attention at potentially contaminated (handwashing is strongly recommended) toilets  Cleaning shoes after visit of unclean foreign/field toilets. Therapy (Treatment):  Drugs of choice are: 1. Mebendazole (2100 mg daily for 3 days) 2. Albendazole (1400 mg adults; children below 2 years: 115 mg/kg bodyweight)  Other anthelmintics: piperazine, levamisole, pyrantel or fenbendazole  In the case of intestinal obstruction by massive amounts of worms, a chirurgical intervention (surgery) is needed