Chinese Lantern OVA Nematodes Life Cycle Stages Quiz and Flashcards

Study Notes

Intestinal Nematodes

Larval stages of hookworms and Strongyloides: considered as feeding stage, larvae with an open mouth, shorter and robust than filariform larva, not infective.
Filariform larva: esophagus is uniform throughout, considered as the non-feeding stage, larvae with a closed mouth, longer and slender than rhabditiform larva, infective stage.

Intestinal Parasites

Ascaris Lumbricoides (roundworms): largest intestinal nematode, common name: giant intestinal roundworm, disease: ascariasis, habitat: intestinal tract, infective stage: ingestion of embryonated ova (fertilized or unfertilized eggs).
Ancylostoma Duodenale & Necator Americanus (hookworms): disease: hookworm infection, habitat: large intestine, infective stage: ingestion of embryonated ova.
Trichuris Trichiura (whipworms): disease: trichuriasis, habitat: large intestine, infective stage: ingestion of embryonated ova.

Diagnostic Stage

Necator Americanus: diagnostic stage: filariform larva, mode of transmission: skin penetration.
Trichuris Trichiura: diagnostic stage: adult worm, mode of transmission: ingestion of embryonated ova.
Capillaria Philippinensis: diagnostic stage: adult worm, mode of transmission: ingestion of raw or undercooked fish.

Zoonotic/Non-Human Infection

Ascaris of dogs: can infect humans, called ascaris.
Toxocara Canis: can infect humans, disease: visceral larva migrans, transmission: accidental ingestion of embryonated eggs.
Ancylostoma Caninum: can infect humans, disease: cutaneous larva migrans, transmission: skin penetration.
Dirofilaria Immitis: can infect humans, disease: produce peripheral nodules in the lungs, transmission: mosquito bite.

Extra-Intestinal Mode of Transmission

Trichinella Spiralis: transmission: consumption of raw or undercooked meat, especially pork.
Dracunculus Medinensis: transmission: ingestion of contaminated water.

Ascaris Lumbricoides

Largest intestinal worm: soil-transmitted helminth, ova: regularly ovoid, with thick shell, cytoplasm contains organized germ cells.
Adult: lives primarily in jejunum, female: contains egg in its body, body is divided into two parts: anterior and posterior, two types: typical and atypical female.
Male: has caudal alae, single spicule and unspined sheath, slender than female, stichosome: esophageal structure with rows of secretory cells.

Hookworms

Necator Americanus, Ancylostoma Duodenale, Ancylostoma Caninum, Ancylostoma Braziliense: blood-sucking nematodes causing anemia, attached to intestinal mucosa, soil-transmitted helminths, capable of heart-lung migration.
Ova: all hookworm eggs are alike, ovoid, with thin hyaline transparent shell, contains 2-8 germ cells.
Adult: has a mouth/buccal cavity with dental pattern, Necator americanus: with semilunar cutting plates, Ancylostoma duodenale: with 2 pairs of teeth, Ancylostoma caninum: with 3 pairs of teeth, Ancylostoma braziliense: with 1 pair of teeth.
Copulatory bursa: structure found among male nematode used for copulation, parts: copulatory spicules and dorsal rays.

Strongyloides Stercoralis

Smallest nematode of a man: capable of heart-lung migration, mode of living: facultative (free-living/parasitic), parthogenic: can produce eggs even without male.
Ova: similar to those of hookworms, eggs smaller than those of hookworms, contains larva, referred to as “Chinese Lantern Ova”.
Larval stages: L1: Rhabditiform (feeding stage), L3: Filariform (infective stage).

Dracunculus Medinensis

Named by Galen: not a true filaria, larva: have a well-developed digestive tract, never found in blood or tissues of the host, discharged directly into the water.
Female: ovoviviparous parasite, blister to form, male: inconspicuous.

Trichinella Spiralis

Parasite of carnivorous mammals: common in rats and in swine fed uncooked garbage, may occur in humans who consume uncooked pork.
Larva: encysted larva is the diagnostic and infective stage, fully developed, coiled in a spiral and gradually become surrounded by a sheath drive from muscle fibers.
Adult female: larger, straight, pointed tail, viviparous, single club-shaped uterus containing larva, single ovary.
Male: curved posteriorly, possesses two pairs of conical papillae, single testis, cloaca found at the caudal end, absent spicule.

Angiostrongylus Cantonensis

Other name: parastrongylus cantonensis: final/definitive host: Rattus Norvegicus, Rattus Rattus, accidental host: humans, intermediate host: mollusk/snail, paratenic host: prawn, crab, vegetation.
Infective stage: L3 larva to rats, L1 larva to slugs and land snails.
Adult: equipped with a uterus with barber’s pole appearance.

Description

Test your knowledge on the different life cycle stages of nematodes such as hookworms, Strongyloides, and Ascaris Lumbricoides. Identify characteristics of feeding and infective larval stages in this quiz.