Veterinary Parasitology: Nemathelminthes

Veterinary Parasitology: Helminthology and Immune Parasitology

• Course Code: PAR314
• Instructor: Dr. Mohamed Abdelmoghny
• Contact Information: Provided on the title slide

Phylum: Nemathelminthes

• Includes rounded, unsegmented, bilaterally symmetrical worms (free-living or parasitic)
• Parasitic worms may have obligatory parasitic phases and free-living phases during their lifecycle.
• Nematodes are commonly called "roundworms" due to their appearance in cross-section

Class: Nematoda (Round Worms)

• General Characteristics:
  • Unsegmented and bilaterally symmetrical, elongated, cylindrical bodies tapering at both ends.
  • Flesh-colored bodies covered by a cuticle.
  • Varying lengths, from millimeters to over a meter.
  • Digestive system and body cavity (pseudocoelom).
  • Cuticle is smooth and finely striated, developed from the hypodermis.
  • Lack cilia, limbs, respiratory, or circulatory systems.
  • Possess structures (lips, teeth, hooks, plates, or papillae) for attachment to hosts.
  • Sexes separate; males are smaller, shorter, and thinner than females.
  • Males often have a tail with a bursa or copulatory spicules for grasping females during copulation.

General Morphology: External Structure

• Body Wall: Composed of three layers: cuticle, hypodermis, and muscular layer.
  • Cuticle: Colorless, translucent, elastic, secreted by the hypodermis. It protects internal organs and may shed multiple times during development. May have lateral expansions.
  • Hypodermis: Layer of hypodermal cells that project into the body cavity. Forms lateral, dorsal, and ventral cords. Contains excretory and nerve canals.
  • Muscular Layer: Consists of a single layer of longitudinal muscle cells, lying between the hypodermis and the body cavity. Enables locomotion through undulating waves of muscle contraction and relaxation.

General Morphology: Internal Structure

• Digestive System: A simple, straight tube extending from the mouth to the anus.

  • Mouth: Simple opening, may have lips or a leaf-like crown.
  • Buccal Capsule: A tubular structure for sucking purposes, may be present/absent and have teeth or cutting plates.
  • Esophagus: Can be simple, club-shaped, double-bulbed, rhabditiform, or filariform depending on the species.
  • Intestine: A tube-like structure. In females, typically ending in a distinct anus, in males often opening into a cloaca which also receives other reproductive ducts, and the posterior part is the tail.

• Excretory System: Two lateral excretory ducts that run within the lateral cords and open through an excretory pore near the esophagus. They function in osmoregulation.

• Nervous System: A ring of nerves surrounds the esophagus, with ganglia and nerve trunks running anteriorly and posteriorly.

• Vascular System: No circulatory system; fluid-filled body cavity (pseudocoelom) contains oxygen-carrying pigments like oxyhaemoglobin. This body cavity fluid maintains turgor.

• Reproductive System: Unisexual (separate sexes); female reproductive system has paired ovaries, oviducts, uterus, and a vagina that opens at the vulva. Male system has testes, vasa deferens, seminal vesicles, and ejaculatory ducts that open into a cloaca (sometimes with spicules and/or bursa).

Types of Oesophagus

• Simple Club/Bulb-shaped/Balloon Shaped
• Double-bulbed
• Rhabditiform
• Filariform
• Cylindrical/Muscular-glandular
• Cellular/Trichuroid

General Life Cycle and Developmental Stages of Nematodes

• Oviparous/Viviparous/Larviparous/Ovoviviparous: Reproductive strategies of egg producing in females.
• Lifecycle Direct/Indirect: A life cycle can be with or without an intermediate host during their development
• Larval Stages (L1-L5): Stages of development where the larvae undergo molting, typically in the free-living phase.
• Preparasitic Stages: Depending on species, different egg stages may be considered preparasitic and may contain developed/immature larvae

Parasitic Nematode of Veterinary Importance: Simplified Classification

(Extensive lists of nematode species with characteristics and various life cycles)

Ascarids of Pigs/Men/Equine/Ruminants/Dogs/Cats/Poultry

(Specific anatomy, lifecycle details, and clinical signs related to different species)

Visceral Larval Migrans (VLM)

(Information on pathogenesis, clinical symptoms, diagnosis, treatment, and control measures for human infections with nematode larvae)

This quiz covers the essential characteristics and life cycles of Nematodes, including their classification and physiological traits. Dive deep into the Phylum Nemathelminthes and enhance your understanding of these parasitic and free-living roundworms.