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Ascaris Lumbricoides

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Ascaris Lumbricoides Ascaris Lumbricoides -Ascariasis is caused by the parasitic roundworm Ascaris lumbricoides. Perhaps as many as one quarter of the world's people ... – PowerPoint PPT presentation

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Title: 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.

7
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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 Loefflers 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 550 g 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, 1535 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
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