Nematodes and Parasitic Roundworms

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Questions and Answers

What is the characteristic feature of the anterior and posterior ends of Trichuris trichiura?

Presence of phasmids

Presence of amphids (correct)

Absence of sensory organs

Presence of sensory organs

What is the mode of transmission of Capillaria philippinensis?

Ingestion of freshwater fish (correct)

Oro-fecal transmission

Skin penetration

Vector transmission

What is the diagnostic stage of Strongyloides stercoralis?

Rhabditiform larvae (correct)

Adults

Filariform larvae

Embryonated eggs

What is the common name of Enterobius vermicularis?

Pinworm Signup and view all the answers

Which parasitic infection is most common in developed nations?

Enterobiasis Signup and view all the answers

What is the risk factor associated with Enterobius vermicularis infection?

UTI Signup and view all the answers

What is the mode of transmission of Wuchereria bancrofti?

Vector transmission Signup and view all the answers

What is the diagnostic stage of Trichinella spiralis?

Encysted larvae Signup and view all the answers

What is the characteristic feature of the posterior end of Trichuris trichiura?

Presence of phasmids Signup and view all the answers

What is the mode of transmission of Ascaris lumbricoides?

Oro-fecal transmission Signup and view all the answers

What is the characteristic shape of nematode bodies?

Elongated and cylindrical Signup and view all the answers

Which of the following is a characteristic of male nematodes?

Presence of spicules Signup and view all the answers

What is the function of the muscular pharynx in nematodes?

Not specified in the text Signup and view all the answers

What is the characteristic color of nematode bodies?

Light cream-white Signup and view all the answers

What is the characteristic of the body wall of nematodes?

Outer, hyaline noncellular cuticle Signup and view all the answers

What is the characteristic of the digestive system of nematodes?

Complete digestive system Signup and view all the answers

What is the primary mechanism by which Trichinella spiralis is liberated from pork?

Through the action of gastric juices Signup and view all the answers

During which phase of Trichinella infection does larval migration occur?

Invasion phase Signup and view all the answers

What is the primary cell type involved in the encystment of Trichinella spiralis in striated skeletal muscle?

Host-derived cells (nurse cells) Signup and view all the answers

What is the primary diagnostic test for Trichinella infection?

Muscle biopsy Signup and view all the answers

What is the primary treatment for Trichinella infection?

Albendazole Signup and view all the answers

What is a common laboratory finding in Trichinella infection?

Eosinophilia Signup and view all the answers

What is the shape of the eggs of E. Vermicularis?

D-shaped Signup and view all the answers

What is the time interval from ingestion of infective eggs to oviposition by the adult females of E. Vermicularis?

One month Signup and view all the answers

What is the life span of adult E. Vermicularis?

Two months Signup and view all the answers

What is the habitat of adult E. Vermicularis?

Cecum Signup and view all the answers

What is the treatment for E. Vermicularis infection?

Mebendazole or Albendazole or Pyrantel pamoate Signup and view all the answers

What is the characteristic feature of E. Vermicularis eggs?

Inner lipoidal membrane Signup and view all the answers

What is the common presentation of E. Vermicularis infection?

Pruritus ani Signup and view all the answers

How do the larvae of E. Vermicularis infect the host?

Through ingestion of infective eggs Signup and view all the answers

What is the primary diagnostic method for Trichiura?

Direct fecal smear Signup and view all the answers

What is the natural definitive host of Capillaria philippinensis?

Fish-eating birds Signup and view all the answers

What is the characteristic feature of the esophagus in Capillaria philippinensis?

Has rows of secretory cells Signup and view all the answers

What is the treatment of choice for Capillaria philippinensis?

Albendazole Signup and view all the answers

What is the characteristic feature of the larva of Trichinella spiralis?

Spear-like burrowing anterior tip Signup and view all the answers

What is the intermediate host of Trichinella spiralis?

Pigs Signup and view all the answers

What is the characteristic feature of the male Trichinella spiralis?

Has a single testis Signup and view all the answers

What is the characteristic feature of the female Trichinella spiralis?

Has an oviduct, seminal receptacle, coiled uterus, vagina, and vulva Signup and view all the answers

Study Notes

Nematodes (Roundworms)

Intestinal Nematodes

Capillaria philippinensis: also known as Pudoc's worm or mystery worm; only nematode whose life cycle involves a migratory bird; natural definitive hosts are fish-eating birds, and incidental definitive hosts are humans; intermediate hosts are freshwater or brackish water fish.
Ascaris lumbricoides: also known as giant intestinal roundworm, lumbricus teres, or eeworm; largest nematode of man; most common nematode infecting man; soil-transmitted helminth (STH); has heart-lung larval migration.
Trichuris trichiura: also known as whipworm; eggs are "D-shaped" and have a triple albuminous covering, an inner lipoidal membrane, and no glycogen layer; eggs become infective outside the host for 4-6 hours.

Extra-Intestinal Nematodes

Filarial Nematodes: includes Wuchereria bancrofti, Brugia malayi, and Loa loa; transmitted by mosquitoes or flies; infective stage is L3 larvae; diagnostic stage is microfilariae in blood or skin.
Trichinella spiralis: also known as Trichina worm, Muscle worm, or Garbage worm; has three subspecies: T. spiralis spiralis, T. spiralis nativa, and T. spiralis nelsoni; hosts serve as both final and intermediate hosts; intermediate hosts are pigs.

General Characteristics

Body structure: elongated, unsegmented bodies with cylindrical shape and bilateral symmetry; complete digestive tract; no circulatory system; light cream-white color; separate sexes, some are pathenogenetic.
Muscular pharynx: triradiate.
Supporting body wall: outer, hyaline noncellular cuticle; subcuticular epithelium; layer of muscle cells.
Sensory organs: amphids in anterior ends and phasmids in posterior ends.

Diagnostic Tools

Basic diagnostic tool: agents, modes of transmission, infective stages, and diagnostic stages.
Eggs: morphology and characteristics vary depending on the species.
Larvae: morphology and characteristics vary depending on the species.

Salient Features and Presentation

Enterobius vermicularis: most common helminth infection in developed nations; most common cause of pruritus ani among school-aged children; increases the risk for UTI; can be transmitted via inhalation of eggs or ingestion of embryonated eggs.
Ascaris lumbricoides: largest nematode of man; most common nematode infecting man; soil-transmitted helminth (STH); has heart-lung larval migration.
Capillaria philippinensis: only nematode whose life cycle involves a migratory bird; natural definitive hosts are fish-eating birds, and incidental definitive hosts are humans; intermediate hosts are freshwater or brackish water fish.
Trichinella spiralis: host serves as both final and intermediate host; intermediate hosts are pigs; three subspecies: T. spiralis spiralis, T. spiralis nativa, and T. spiralis nelsoni.

Diagnosis and Management

Diagnosis: varies depending on the species, but may include direct fecal smear, Kato Thick smear, Kato Katz smear, Scotch tape test, or muscle biopsy.
Treatment: varies depending on the species, but may include Albendazole, Mebendazole, or Pyrantel pamoate.

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Description

This quiz covers different types of nematodes, including intestinal and extra-intestinal parasites, such as hookworms, filarial nematodes, and trichinella spiralis.