Ascaris Lumbricoides

1. Ascaris Lumbricoides

2. Ascaris Lumbricoides -Ascariasis is caused by the parasitic roundworm Ascaris lumbricoides. Perhaps as many as one quarter of the world's people are infected. It is the largest of the intestinal nematodes parasitizing humans. -It is the most common worm found in human ,and it is worldwide in distribution and most prevalent in tropic areas with more prevalent in the countryside than in the city

3. Adult worm of A. lumbricoides

4. Factors favoring the spread of the transmission: 1.Simple life cycle. 2. Enormous egg production ( 240,000 eggs/ day/ female). 3. These eggs are highly resistant to ordinary disinfectants.The eggs may remain viable for several years. 4. Social customs and living habits. 5. Disposal of feces is unsuitable.

5. Life Cycle 1.Site of inhabitation: small intestine 2. Infetive stage: embryonated eggs 3. Route of infection: by mouth 4. No intermediate and reservoir hosts 5. Life span of the adult worm: about 1 year-This worm lives in the lumen of small intestine, feeding on the intestinal contents, where the fertilized female lays eggs. An adult female can produce approximately 200,000 eggs per day, which are passed in feces. When passed, the eggs require outside development of about three weeks until a motile embryo is formed within the egg.

6. - After the ingestion of embryonated eggs (infective) 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 circulation to the liver,heart and finally to the lungs where they penetrate the capillaries into the alveoli in which they molt twice and stay for 10-14days. -Then they are carried, or migrate, up the bronchioles, bronchi, and trachea to the thorate. When swallowed, the larvae pass down into the small intestine where they develop into adults. -The time from the ingestion of embryonated eggs to oviposition by the females is about 60-75 days. The adult worms live for about one-two year.

8. 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.

9. 2. 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. -More serious manifestations have been observed. Adults worm may block the the common bile duct and even perforate the intestinal wall. -Thus complications of ascariasis, that may occur include intestinal obstruction, appendicitis, biliary ascariasis, perforation of the intestine, pancreatitis and peritonitis, enlargement of the liver or spleen, etc. -other complications, sometimes fatal, include obstruction of the bowel by a bolus of worms (observed particularly in children). More than 796 Ascaris lumbricoides worms weighing 550g [19 ounces] were recovered at autopsy from a 2-year-old South African girl. The worms had caused torsion and gangrene of the ileum, which was interpreted as the cause of death.

10. Source Ingestion of infective eggs from soil contaminated with human feces or transmission and contaminated vegetables and water is the primary route of infection. -Intimate contact with pets which have been in contact with contaminated soil may result in infection, while pets which are infested themselves by a different type of roundworm can cause infection with that type of worm. -Transmission also comes through municipal recycling of wastewater into crop fields. This is quite common in emerging industrial economies, and poses serious risks for not only local crop sales but also exports of contaminated vegetables. A 1986 outbreak of ascariasis in Italy was traced to irresponsible wastewater recycling used to grow vegetable exports . -Transmission from human to human by direct contact is impossible.

11. Diagnosis The confirmative diagnosis depends on the recovery and identification of the worm or its egg. 1. Ascaris pneumonitis: examination of sputum for Ascaris larvae is sometimes successful. 2. Intestinal ascariasis: feces are examined for the ascaris eggs. (1) direct fecal film: 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. (3) On X-ray, 15–35 cm long filling defects, sometimes with whirled appearance (bolus of worms).

12. Treatment Drugs that are used to kill roundworms are called ascaricides and include: 1-Benzimidazole derivatives : a-Mebendazole Causes slow immobilization and death of the worms by selectively and irreversibly blocking uptake of glucose and other nutrients in susceptible adult intestine. Drug interactions -Carbamazepine and Phenytoin lowers serum levels of mebendazole. Cimetidine raises serum mebendazole levels, increasing its effectiveness. -Stevens-Johnson syndrome (toxic epidermal necrolysis) when Mebendazole is combined with high doses of Metronidazole.

13. b-Albendazole A broad-spectrum antihelminthic agent that decreases ATP production in the worm, causing energy depletion, immobilization, and finally death. -It causes degenerative alterations in the intestinal cells of the worm by binding to the colchicine-sensitive site of tubulin, thus inhibiting its polymerization or assembly into microtubules. The loss of the cytoplasmic microtubules leads to impaired uptake of glucose by the larval and adult stages of the susceptible parasites, and depletes their glycogen stores. Degenerative changes in the endoplasmic reticulum, the mitochondria of the germinal layer, and the subsequent release of lysosomes result in decreased production of adenosine triphosphate (ATP), which is the energy required for the survival of the helminth. Due to diminished energy production, the parasite is immobilized and eventually dies. -Contraindicated during pregnancy and children under 2 years.

14. Albendazole may cause dizziness, headache, fever, nausea, vomiting, or temporary hair loss. In rare cases it may cause persistent sore throat, severe headache, seizures, vision problems, yellowing eyes or skin, dark urine, stomach pain, easy bruising, mental/mood changes, very stiff neck, change in amount of urine. Allergic reactions are also possible. -CBC and hepatic functions have to be obtained regularly in patients receiving Albendazole.

15. c-Thiabendazole This may cause migration of the worm into the esophagus, so it is usually combined with piperazine.

16. 2-Piperazine -Piperazines were originally named because of their chemical similarity with piperidine, a constituent of piperine in the black pepper plant -Generally it acts by paralysing parasites, which allows the host body to easily remove or expel the invading organism. This action is mediated by its agonist effects upon the inhibitory GABA receptor. Its selectivity for helminths is because vertebrates only use GABA in the CNS and the helminths' GABA receptor is a different isoform to the vertebrate's one. -(i.e) It is a flaccid paralyzing agent that causes a blocking response of ascaris muscle to acetylcholine. The narcotizing effect immobilizes the worm, which prevents migration when treatment is accomplished with other drugs such as albendazole. If used by itself it causes the worm to be passed out in the feces.

17. 3-Pyrantel pamoate It is a combination of pyrantel and pamoic acid. -Pyrantel pamoate acts as a depolarizing neuromuscular blocking agent, thereby causing sudden contraction, followed by paralysis, of the helminths. This has the result of causing the worm to "lose its grip" on the intestinal wall and be passed out of the system by natural process. Since Pyrantel is poorly absorbed by the hosts intestine, the small dosage of medication used is completely ineffective to the host. -Spastic (tetanic) paralyzing agents, in particular pyrantel pamoate, may induce complete intestinal obstruction in a heavy worm load. -Worms usually pass in normal stool or with diarrhea, straining, and occasional vomiting. -P.S. : Pyrantel pamoate is considered a Pregnancy category C drug for use during pregnancy for humans