PARA-Class-Nematoda-2024

The Nematodes

Overview

  • Nematodes, also known as roundworms, are a diverse group of worms classified under the phylum Nematoda.

Classification

A. Intestinal Nematodes

  • Ascaris lumbricoides

  • Trichuris trichiura

  • Hook worms

    1. Ancylostoma duodenale

    2. Ancylostoma caninum

    3. Ancylostoma braziliensis

    4. Necator americanus

  • Strongyloides stercoralis

  • Enterobius vermicularis

  • Capillaria philippinensis

B. Tissue Nematodes

  • Trichinella spiralis

  • Dracunculus medinensis

  • Angiostrongylus cantonensis

C. Filarial worms

  • Wuchereria bancrofti

  • Brugia malayi

  • Onchocerca volvulus

  • Loa Loa

General Characteristics of Nematodes

  • Body Structure: Unsegmented and cylindrical, tapered at both ends.

  • Cuticle: Bodies are covered with a protective cuticle.

  • Digestive System: Complete digestive tract observed.

  • Sexual Dimorphism: Separate sexes; females are larger than males (females have straight tails while males have curved tails with spicules for copulation).

  • Color: Generally light cream to white.

  • Life Cycle Stages: Include egg, larvae, and adults with dioecious reproduction.

Focus on Ascaris lumbricoides

General Information

  • Common Name: Giant Intestinal Roundworm.

  • Disease: Ascariasis; may cause pneumonia and intestinal blockage ("worm ball").

  • Habitat: Small intestine.

Transmission and Lifecycle

  • Mode of Transmission (MOT): Ingestion of embryonated eggs via fecal-oral route.

  • Infective Stage: Embryonated ova.

  • Diagnosis: Detection of ova/adult worms in stool or through x-ray.

  • Treatment: Anthelmintics such as Albendazole and Mebendazole.

  • Control: Educational awareness, drug therapy, and addressing the disease as a poverty-related condition.

Morphology

Adult Structure

  • Male Size: 150-200 mm long (up to 30 cm).

  • Female Size: 200-300 mm long (20-35 cm). Anterior with tri-lips.

Egg Description
Fertilized Ova

  • Broadly oval (45-75 µm x 35-50 µm) with an albumen coat; typically stained golden brown in fresh stool.

  • Three layers of eggshell:

    1. Inner vitelline membrane (non-permeable)

    2. Thick transparent glycogen membrane (middle)

    3. Outer albuminoid layer.

Unfertilized Ova

  • Longer (90 x 40 µm) with thin inner shell and albuminous coat containing lecithin granules.

Lifecycle Steps

  1. Egg Ingestion: Eggs are ingested by the host, hatch in the small intestine.

  2. Larvae Migration: Larvae invade the intestinal mucosa and travel via bloodstream to lungs.

  3. Adult Development: Adult worms mature in the small intestine, laying eggs excreted in feces.

Other Notable Nematodes

Trichuris trichiura

  • Common Name: Whipworm.

  • Disease: Rectal prolapse, bloody diarrhea.

  • MOT: Ingestion of embryonated eggs; diagnosed via stool examination.

  • Treatment: Albendazole and Mebendazole.

Hookworms

  • Genera: Necator and Ancylostoma.

  • Disease: Ground itch, iron deficiency anemia, affecting the small intestine via skin penetration of larvae.

  • Treatment: Similar to Ascaris, with additional iron supplements for anemia.

Enterobius vermicularis

  • Common Name: Pinworm.

  • Symptoms: Perianal itching.

  • MOT: Ingestion of embryonated eggs or retroinfection.

  • Diagnosis: Scotch-tape method for eggs.

  • Treatment: Albendazole, Pyrantel pamoate.

Capillaria philippinensis

  • Disease: Capillariasis, primarily affecting the small intestine.

  • MOT: Ingestion of contaminated fish, diagnosed by stool examination.

  • Treatment: Similar to Ascaris.

Trichinella spiralis

  • Common Name: Trichina worm.

  • Disease: Muscle migration causing pain.

  • MOT: Ingestion of undercooked pork.

  • Diagnosis: Muscle biopsy or serological tests.

Filarial Worms

General Characteristics

  • Parasitic worms affecting lymphatic and subcutaneous tissues, transmitted by mosquitoes or flies.

  • Key Examples: Wuchereria bancrofti (Filariasis), Brugia malayi, Loa loa (African eye worm).

Transmission and Diagnosis

  • Diagnosis typically through detection of microfilariae in blood or other tissue samples.

Conclusion

  • Nematodes exhibit a variety of species, life cycles, and pathogenic effects, making them a significant concern in both public health and clinical settings.