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21 Cards in this Set

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Enterobius Vermicularis - Clinical Manifestations.
Enterobiasis is most common in children, who usually manifest pruritus ani and sometimes insomnia, abdominal pain, anorexia, and pallor. Genitourinary infection may occur in females.
Enterobius Vermicularis - Structure
Worms are white and spindle-shaped with a large, bulbar esophagus. Males are smaller and have a curved posterior. Eggs are ovoid, thin-shelled, and flat on one side.
Enterobius Vermicularis - Multiplication and Life Cycle
Females usually migrate out the anus at night and depositeggs on the perianal skin. The eggs embryonate quickly and, if ingested, hatch and mature in the intestines.
Enterobius Vermicularis - Pathogenesis
Intestinal lesions are rare; extraintestinal infection may lead to complications.
Enterobius Vermicularis - Host Defenses
The defenses are little known. Most infections occur in children.
Enterobius Vermicularis - Epidemiology
Enterobius vermicularis is the most common helminth in the United States. Household and institutional epidemics occur, usually in children. Transmission is usually by hand to mouth transfer of infective eggs.
Enterobius Vermicularis - Diagnosis
Eggs are rare in feces but are readily collected by Scotch-tape perianal swabs.
Enterobius Vermicularis - Control
Control is by anthelmintic treatment and by improved personal hygiene, including washing the perianal region and changing nightclothes.
Enterobius Vermicularis - Clinical Manifestations
Enterobiasis, or pinworm infection, usually causes little disease. The most common symptom is pruritus ani, which disturbs sleep and which, in children, may be responsible for loss of appetite. abdominal pain, irritability, and pallor may also be signs of enterobiasis. The parasite has been suspected as a cause of appendicitis, and gravid female worms have been known to migrate up the vagina and fallopian tubes and into the peritoneal cavity, where they become encapsulated with granulomatous tissue. Recurrent urinary tract infections have been attributed to ectopic pinworm infections.
Enterobius Vermicularis - Structure
The whitish, spindle-shaped worms have characteristic cephalic swellings (alae) and a large muscular esophagus with a large posterior bulb. Females are approximately 1 cm long and males are half that size. The curved posterior end of male worms has a single copulatory spicule. The males are rarely seen because they die shortly after copulation and are expelled. The eggs are thin-shelled, ovoid, flattened on one side, and measure 50 to 60 μm by 20 to 30 μm.
Enterobius Vermicularis - Anterior part of pin worm
Enterobius Vermicularis - Showing esophageal bulb and swollen cuticle at the head end
Posterior end of a male . Arrow shows single spicule
Posterior end of a female E. Vermicularis Eggs of E. vermicularis 50-60 micro m
Enterobius vermicularis - Multiplication and Life Cycle
The parasites mature in the large intestine. When gravid, female worms migrate out of the anus at night when the anal sphincter is relaxed and lay eggs that adhere to the perianal skin. The female essentially ruptures, releasing as many as 10,000 eggs. The eggs embryonate and become infective within a few hours after being deposited onto the skin. Infection is transmitted hand-to-mouth. The ingested eggs hatch in the small intestine, each releasing an infective stage larva. The parasite moves to the cecum and matures into an adult 2 to 4 weeks after infecting the host). Infections are self-limited; reinfection can occur.
Life cycle of Enterobius vermicularis..
Enterobius vermicularis - Pathogenesis
Intestinal lesions are reported, but the worms usually cause little intestinal pathology. The parasite has been found in diseased appendices but is not necessarily the cause of the pathology. Pinworms can make their way to extraintestinal locations and cause complications. For example, the parasites may carry bacteria into other organs, resulting in abscess formation.
Enterobius vermicularis - Diagnosis
Children suffering sleepless nights because of perianal itching often have pinworms. Eggs are rarely found in the feces, and the diagnosis is made by finding eggs on perianal swabs made of Scotch tape. The tape is pressed first onto the perianal region and then onto a microscope slide, and is examined microscopically. Perianal specimens are best obtained in the morning before bathing or defecation. Three specimens should be taken on consecutive days before pinworm infection is ruled out.
Host Defenses
Little is known about immune responses to pinworm infection. Infections are more common in children than in adults, suggesting that acquired immunity or some other type of age-related resistance develops. IgE immunoglobulin serum levels in patients are reported to be within normal limits.
Epidemiology
It is safe to say that everyone, at one time or another, has pinworms. It is a cosmopolitan parasite found most often in families and in institutionalized children. The parasite is transmitted hand-to-mouth after scratching the perianal region, by handling contaminated bedding and night clothing, or by inhaling eggs in airborne dust. Eggs will not embryonate at temperatures below 23°C, but embryonated eggs remain viable for several weeks under moist and cool conditions.
Prevalence rates for E vermicularis are highest in temperate regions. It is estimated that more than 200 million persons are infected. In the United States, pinworm is considered the most common helminthic infection. No animal reservoir exists for E vermcularis,although dogs and cats have been incriminated erroneously.
Enterobius vermicularis - Control
When an infection is recognized, efforts should be made to improve personal hygiene. Fingernails should be cut short, the perianal region washed in the morning, and bedding and sleeping garments washed daily. Other members of a patient's family should be checked; the entire family may need treatment to eliminate infection. Although several anthelmintics are effective in treating enterobiasis, the drugs presently recommended are pyrvinium pamoate, pyrantel pamoate, and mebendazole. It is advisable to re-treat the patient one month later.