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Ascaris lumbricoides

Ascaris lumbricoides. Ascaris lumbricoides also called common round worm Most common intestinal nematode of the human Habitat : adult worm lives in small intestine, particularly jejunum and middle part of ileum.

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Ascaris lumbricoides

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  1. Ascarislumbricoides

  2. Ascarislumbricoides also called common round worm • Most common intestinal nematode of the human • Habitat: adult worm lives in small intestine, particularly jejunum and middle part of ileum

  3. Ascarislumbricoides , commonsaying “round worm of man”, is the largest of the intestinal nematodes parasitizing humans. • It is the most common worm found in human. • It is worldwide in distribution and most prevalent through out the tropics, sub-tropics and more prevalent in the countryside than in the city.

  4. Adult worm: • Freshly passed adult worms in the stool are pink in colour and look like earth worms • Large and cylindrical with tapering ends • Anterior end is thinner and more attenuated than the posterior end • The worm has a small mouth surrounded by 3 lips, dorsal and 2 ventral • Digestive and reproductive organs float in the fluid present inside the body cavity • Adult worms live in the small intestine for 6 months or little more

  5. Adult worm of A. lumbricoides

  6. Ascaris lumbricoides Female Male

  7. Adult males are relatively smaller than the females ( 15cm to 30cm in length) • Female worms are larger measuring 20cm to 40cm in length • The tail of the male worm is curved ventrally to form a hook-like structure with a conical tip • The tail of the female worm is straight and conical but not curved or pointed

  8. Male genitalia consists of a single coiled tubule comprising of testes, vas deferens and ejaculatory duct • This opens at the cloaca, a pair of copulatoryspicules of equal size arises from the cloaca • Female worm has a minute vulva opening at the junction of anterior and middle third of the body on the mid-ventral part of the worm • This is the narrowest part of the worm called as waist • A single gravid female produces as many as 240,000 eggs per day and as many as 65 million in its lifetime

  9. Ascaris lumbricoides cont. Female gut oviduct genital pore uterus vagina

  10. Ascaris lumbricoides cont. Male sperm duct seminal vesicle testes gut

  11. Egg: There are three kinds of the eggs. They are fertilized eggs, unfertilized eggs and decorticated eggs. • We usually describe an egg in 5 aspects: size, color, shape, shell and content.

  12. Infective form: Embryonated eggs • Egg: both fertilised and unfertilised eggs are present in faeces • Fertilised egg: • Produced by fertilised females • These are oval to subspherical in shape and measure 45um to 70um in length and 35 μm to 50 μm in breadth • They are bile-stained and golden brown in colour • It is surrounded by thick shell with a light brown albuminous outer coat • In some eggs this outer coat is lost and are called as decorticated eggs

  13. Fertilized Ascaris Egg A fertilized Ascaris egg, still at the unicellular stage, as they are when passed in stool. 

  14. Each egg contains a large unsegmented ovum with a clear crescentric area at each pole • The eggs characteristically float in the saturated salt solution • Unfertilised egg: • Are brown thin-shelled measure 78μm to 105 μm in length and 38 μm to 55 μm in breadth • These are heaviest of all the helminthic eggs hence donot float in saturated salt solution

  15. Unfertilized egg: Longer and slender than a fertilized egg. • The chitinous layer and albuminous coat are thinner than those of the fertilized eggs without ascaroside and fertilizing membrane. • The content is made of many refractable granules various in size.

  16. Decorticated eggs: Both fertilized and unfertilized eggs sometimes may lack their outer albuminous coats and are colorless.

  17. Freshly passed fertilised eggs are not infective to man • They require 10 to 40 days for development into embryonated eggs • Only embryonated eggs are infective to man

  18. Life Cycle • 1.Site of inhabitation: small intestine 2. Infective stage: embryonated eggs 3. Route of infection: by mouth 4. No intermediate and reservoir hosts 5. Life span of the adult: about 1 year

  19. Man acquires infection by ingestion of embryonated eggs in contaminated food or drink or from contaminated fingers • Host digestive juices acts on the egg shell and liberate the larva into the small intestine. • These larvae penetrate the intestinal mucosa and enter lymphatics and mesenteric vessels. • They are carried by portal circulation to the liver where they live for 3-4 days • Then taken to right heart and finally to the lungs where they penetrate the pulmonary capillaries into the alveoli in which they moult twice and becomes 4the stage larva

  20. The larva then breaks out of the capillaries and reach alveoli • From there they migrate up the bronchioles, bronchi, and trachea to the epiglottis. • When swallowed, the larvae pass down into the small intestine where they develop into adults. • Moulting takes place again and larva grows to become adult and matures sexually in 6-10 weeks of infection • The time from the ingestion of embryonated eggs to oviposition by the females is about 60-75 days.

  21. The eggs containing unsegmented ovum passed in the faeces are not infective to man • In moist soil with a temperature of 20-400C and humidity over 40%, a 1st stage rhabditiform larva develops inside the egg in 10-15 days • This undergoes moulting to become 2nd stage larva • The embryonated eggs containing these 2nd stage rhabditiform larvae are infective to man if consumed with food

  22. Ascarislumbricoidesworms have a reputation for wandering, and often do so if the body they are in-the host-is ill or taking certain medications. • Adult roundworms sometimes spontaneously exit the host through the anus, mouth, or nose. • They are found in the bathtub, toilet bowl, in diapers, or even on the pillow upon waking.

  23. Pathogenesis There are two phase in ascariasis: 1. The blood-lung migration phase of the larvae: • During the migration through the lungs, the larvae may cause a pneumonia. • The symptoms of the pneumonia are low fever, cough, blood-tinged sputum, asthma. • Large numbers of worms may give rise to allergic symptoms. • Eosionophilia is generally present. • These clinical manifestation is also called Loeffler’s syndrome.

  24. The intestinal phase of the adults. • The presence of a few adult worms in the lumen of the small intestine usually produces no symptoms, but may give rise to vague abdominal pains or intermittent colic, especially in children. • A heavy worm burden can result in malnutrition. • Wandering adults may block the appendical lumen or the common bile duct and even perforate the intestinal wall • Intestinal obstruction

  25. Thus complications of ascariasis, such as intestinal obstruction, appendicitis, biliaryascariasis, perforation of the intestine, cholecystitis, pancreatitis and peritonitis, etc., may occur, in which biliaryascariasis is the most common complication.

  26. Diagnosis • The symptoms and signs are for reference only. • The confirmative diagnosis depends on the recovery and identification of the worm or its egg. 1. Ascarispneumonitis: examination of sputum for Ascaris larvae is sometimes successful. 2. Intestinal ascariasis: feces are examined for the ascaris eggs.

  27. 1. Stool examination: it is simple and effective. The eggs are easily found using this way due to a large number of the female oviposition, approximately 240,000 eggs per worm per day. So this method is the first choice. 2. Recovery of adult worms: when adults or adolescents are found in feces or vomit and tissues and organs from the human infected with ascarids , the diagnosis may be defined.

  28. Ascaris Worms in Intestine

  29. Epidemiology • World wide distribution, very common in China, especially in the countryside. Factors favoring the spread of the transmission: 1.Simple life cycle. 2. Enormous egg production ( 240,000 eggs/ day/ female ).

  30. 3. These eggs are highly resistant to ordinary disinfectants( due to the ascroside). The eggs may remain viable for several years. 4. Social customs and living habits. 5. Disposal of feces is unsuitable.

  31. Prevention and Treatment • 1.Treatment to ascariasis:Mebendazole, Albendazole and Levamizole are effective. • 2.Sanitary disposal of feces. • 3.Hygienic habits such as cleaning of hands before meals. • 4.Health education.

  32. Prevent the following: • Drinking or eating raw vegetables contaminated by the infective eggs • Eating soil frequently seen in children • Putting soiled fingers and toys contaminated with eggs, in the mouth

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