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Questions and Answers
What is the largest reported geographical distribution of any helminth?
Which age group has the highest prevalence of Enterobiasis?
What is the main mode of transmission for Enterobius vermicularis?
Which part of the body is infected by Enterobius vermicularis?
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Where do adult Ascaris worms primarily reside in the human body?
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What facilitates the infection of Enterobius vermicularis in humans?
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How are Ascaris eggs primarily transmitted to humans?
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How do Enterobius vermicularis eggs typically enter the human body?
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How do Ascaris worms protect themselves from being digested by the host?
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What is a potential consequence of high numbers of adult Ascaris worms in the human body?
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Which treatment is effective against adult Ascaris worms but not larval stages?
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Where do adult female Enterobius vermicularis worms primarily settle in the human body?
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How many eggs can an adult female Enterobius vermicularis produce approximately?
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What symptom is commonly associated with Enterobius vermicularis infection?
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What is the most common complication of Enterobius vermicularis infection?
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Which anthelmintic therapy is mentioned as effective against Enterobius vermicularis?
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What is the most common human helminthic infection according to the text?
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For how long can Ascaris lumbricoides eggs survive in favorable conditions of moist, sandy soil?
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Study Notes
Enterobius Vermicularis (Pinworm)
- Habitat: Upper small intestine, mature in 5-6 weeks without migration
- Size: Males 2-5 mm long, 0.3 mm in diameter; females 8-13 mm long, up to 0.6 mm in diameter
- Inhabit: Caecum, appendix, and adjacent portions of the ascending colon
- Female worms migrate out of the anus to lay eggs, usually at night, due to drop in host body temperature
- Eggs embryonate and become infective within 6 hours of deposition
- Infectivity: Up to 2 weeks in cool, humid climates; 2 days in warm, dry conditions
Pathology and Pathogenesis
- Migration of worms out of the GIT to the anus causes local perianal irritation and pruritus
- Scratching leads to contamination of fingers, especially under fingernails, contributing to autoinfection
- Finger sucking and nail biting may be sources of recurrent infection in children
- Spread within families is common
- Most cases are asymptomatic; common symptom is perianal pruritus, especially at night
- Irritability and fatigue from loss of sleep occur, but the infection is relatively benign
Diagnosis and Treatment
- Diagnosis: Recognition of dead adult worms or characteristic ova in a stool O&P test
- Scotch tape or cellophane tape method is the most successful diagnostic method
- Treatment: Mebendazole (100 mg), albendazole (400 mg), repeated after 14 days, with a cure rate of >90%
Ascaris Lumbricoides (Ascariasis)
- Largest nematode infecting humans, with females 25-40 cm long and males 15-30 cm long
- Soil-transmitted infection, with over 1.4 billion people infected worldwide
- Most infections are subclinical; more severe complications occur in children who tend to suffer from the highest worm burdens
- Eggs can survive in the absence of oxygen, live for 2 years at 5-10º C, and be unaffected by desiccation for 2-3 weeks
Life Cycle
- No intermediate host is required
- Intestinal nematodes have cylindrical bodies covered with a tough, acellular cuticle
- The sexes are separate; the male worm is generally smaller than the female, which can produce thousands of eggs
- Female worms produce 200,000 eggs per day, which are passed in the feces and are infectious after about 1 month in the soil
Pathology and Pathogenesis
- Adult worms affect the nutrition status of the host, leading to malnutrition
- Digestive and respiratory organs of the worm float inside the body cavity, possessing a toxic fluid known as ascaron
- Allergic reactions seen in infected individuals are due to this toxin
- If present in high numbers, adult worms may cause mechanical obstruction of the bowel and bile and pancreatic ducts
- Larvae migrating through lungs induce an inflammatory response (pneumonitis)
Diagnosis and Treatment
- Diagnosis: Microscopic examination of stool specimens, recognizing fertilized and unfertilized eggs
- Occasionally, an adult worm is passed via rectum
- Larvae may be detected in sputum
- Eosinophilia may be present, especially during the larval migration through the lungs
- Plain X-ray of the abdomen may reveal a mass of worms
- Serology: Useful for diagnosis
- Treatment: Albendazole and mebendazole are effective therapies for ascariasis; reevaluation of infected individuals is recommended following therapy
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Description
Explore the anatomy of intestinal nematodes, focusing on their cylindrical bodies, tough cuticle, muscle layers, nerve trunks, alimentary tract, and reproductive systems. Learn about the unique features of Enterobius vermicularis.
