Ascariasis

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Ascaris lumbricoides has a worldwide distribution. It is estimated that >250 million people worldwide are infected by this parasite. The highest prevalence is in malnourished people residing in developing countries.
Ascaris lumbricoides is the largest nematode parasitizing the human intestine causing ascariasis.

LIFE CYCLE OF ASCARIS LUMBRICOIDES
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The adult worm inhibits the small intestine usually the jejunum. They have a lifespan of 10 months to 2 years and then are passed out in stool.
When both male and female worm are present in the intestine, each female worm produces 200,000 fertile ova per day. When infection with only female worm occur, infertile eggs that do not develop into the infectious stage are produced. When infected with only male worm, no egg is produced.
The ova are pased out in the faeces and their embryo develop into infective second stage larva in the environment in 2 to 4 weeks depending on the environmental condition.
Man acquires infection by ingestion of food, water and raw vegetables contaminated with the embryonated eggs. In the small intestine, the ingested eggs hatch to liberate the larvae. These larvae burrow their way through the mucous membrane of the small intestine and are carried by the portal circulation to the liver, where they reside for 3 days to 4 days. They then pass via hepatic vein, inferior vena cava, right heart and pulmonary artery and reach the lung. here they grow in size and moult twice ( first on the 5th and second on the 10th day). The larvae then break through the capillary wall and reach the lung alveoli.
From the alveoli, the larvae migrate up to the bronchi, trachea, and larynx, crawl over the epiglottis to the pharynx and are swallowed. They pass down the esophagus and stomach and localize in the upper part of the small intestine, their normal abode.
On 25th to 29th day of infection, the larvae undergo another moulting and transform into adult worms. In about 6 to 10 weeks, they become sexually mature and by 12 weeks the gravid female begins to discharge eggs in stool and the life cycle is repeated.

 CLINICAL PRESENTATIONS

Majority of the infection with Ascaris lumbricoides are asymtopmatic. However, symptomatic diseases worldwide is still relatively high. It may cause;
• Direct tissue damage.
• colicky cramps and loss of appetite.
• obstruction of the intestinal track.
• Nutritional in balance due to the worm.

       PREVENTION AND CONTROL 

• Personal hygiene
• Treatment of infected persons
• Public awareness
• Proper disposal of human faeces
• Avoidance of eating raw vegetables
• Periodic treatment with an effective anthelminthic drugs
• Provision of toilet facilities

          TREATMENT

Anthelminthic medications (drugs that rid the body of parasitic worms), such as albendazole and mebendazole, are the drugs of choice for treatment of Ascaris infections, regardless of the species of worm. Infections are generally treated for 1-3 days. The drugs are effective and appear to have few side effects.

          REFERENCE 

Medical parasitology, third edition by D.R Arora, Brij Bala Arora. Page 192 to 195