HUMAN DISEASES: ASCARIASIS (ROUNDWORM INFECTION)

Introduction: Common Intestinal infection caused by adult nematode Ascaris lumbricoides (Roundworm)

Occurrence/Distribution:

· Cosmopolitan (worldwide), More prevalent in Nepal, India China, Korea, Philippines and South Pacific Islands.

· It is very common in Nepal, especially in those persons with poor hygienic habits.

· Children are more susceptible to ascariasis because they play in the contaminated soil and likely to have it without washing their hands.

· It is the most common worm in Hostel students and children.

· 1/6th of the total population is estimated to be infected with Ascariasis.

Causative organism:
· Ascaris lumbricoides, show sexual dimorphism.
· Male size: up to 20 cm (length), 2-4 mm (diameter), curved tail, shorter.
· Female size: 20-40 cm (length), 4-6 mm (diameter), straight tail, longer.

· Helminth parasite Ascaris lumbricoides that lives in the jejunum of the small intestine.

· After copulation of adult males and females, female Ascaris lays about 200,000 fertilized eggs daily that pass out with the host’s faeces.

· Man acquires infection by directly ingesting the second stage Rhabditoid Larva or Rahbditiform Larva (Develops after 3 weeks) through contaminated food, vegetables and drinks (water).

· They hatch out in the intestine and bore the epithelium of the intestine and reach the liver through the hepatic portal vein.

· From the liver, they reach the heart through the postcaval vein.

· From the heart, they are transported to Lung through the pulmonary artery.

· They moult twice in the lungs and become 4th stage larva.

· They reach the pharynx through the trachea from where they are coughed up and swallowed for the second time reach the gut and become adults.

· Second stage Rhabditoid Larva — Second stage larvae hatching in the intestine — Reach liver through a hepatic-portal vein — Reach heart through a postcaval vein —Reach lung through the pulmonary artery (3rd and 4th stage larvae) — in the intestine through the trachea (4th stage larva) — Young Ascaris — Intestine (Adult male and female Ascaris) — Egg capsules in faeces — 1st stage larva.

Sources of Infection:
· The infected man by ascariasis discharges the embryonated eggs in the faeces. Soil, water and vegetables contaminated by embryonated eggs.

Mode of Transmission:
· Direct or indirect ingestion of embryonated eggs through contaminated food, vegetables, drinks etc, but in children, it is transmitted while playing and ingestion of contaminated soil.

Incubation period: About 60-75 days (average 2 months)

Symptoms:

· Following symptoms are seen in infected persons:
1) Abdominal discomfort, nausea, and colicky abdominal pain.
2) Fever, diarrhoea, indigestion, sometimes vomiting.
3) Heavy infestation of parasites in the intestine causes abdominal distension or mechanical obstruction & may also cause appendicitis.
4) Cough and Pneumonia due to irritation by larvae in the lungs.

· Loffler’s syndrome- Eosinophils accumulate in lungs in response to parasitic infection
5) Liver abscess (swollen due to accumulation of pus) and blockage of bile which crawls. Loss of weight, anaemia, weakness, malnutrition

Diagnosis: Microscopic examination of stool to find the fertilized eggs of Ascaris lumbricoides

Treatment: By using anti-helminthic drugs like Albendazole, Thiabendazole, Mebendazole, Piperazine and Pyrantel pamoate, Oil of Chenopodium, Alcopar, Bendex, Dewormis, Zental etc.

Prophylaxis (Prevention):

· Proper sanitary methods are important to prevent the transmission of disease.
1) Sanitary disposal of human stool to prevent the contamination of soil and no defecation in open areas.
2) Health education regarding the use of sanitary latrines, personal sanitation and encouraging the children to wash their hands with soap water after the toilet and before meals.
3) To avoid contaminated food and drinks.
4) Protection of water sources from contamination by sewage.
5) Improvement in personal hygiene.
6) Government of Nepal has launched deworming programme at places where parasite and protein-energy malnutrition are highly prevalent. In the programme, the mass treatment of children aged 1-5 years is done. They are given Albendazole along with a Vitamin A capsule.

Also, Read our other Notes related to HUMAN DISEASES:

• Human Diseases: Introduction
• Typhoid: Enteric Fever
• Ascariasis: Common Roundworm
• AIDS
• Tuberculosis
• Cancer
• Kalazar
• Hepatitis
• Socially Significant Diseases