General Parasitology and Helminthology: Introduction

Introduction

INTRODUCTION

Nematodes or roundworms are very important group of helminths which infect animals and humans.
The nematodes have both direct and indirect life cycle affecting wide range of animals.
Nematodes are free living/ parasitic and unsegmented, cylindrical in shape.
Nematodes cannot be stained for identification
Some of the nematodes have on their cuticle specialized adhesive structure such as hooks in Tetrameres sp. Cephalic vesicle in Oesophagostomum sp.
Some of the nematodes have lateral flat cuticular expansion called as ‘ Alae”
If the alae is situated in the cervical region it is called as cervical alae and in posterior region as caudal alae.
Alimentary canal is present.
They have a body cavity or coelom. But it is not true coelom. (Pseudo coelom).
The extremities are tapering except the females of Tetrameres spp. which become almost spherical after copulation.
The sexes are separate the body is covered with cuticle. The cuticle is provided with circular annulation or it may be smooth or it may have longitudinal striation.
The cuticle is relatively thick in nature and may extend into the buccal capsule, oesophagus, rectum and distal portion of genital duct.
Sometimes the cuticle forms a special adhesive structure for Eg. Hooks in Tetrameres spp. – male
Simple or complicated cuticular thickening in Gongylonema spp.
Cervical collar or cephalic collar in Physaloptera spp.
Cephalic vesicle in Oesophagostomum spp.
Cuticle is formed by under lying subcuticular layer and muscular layer, the subcuticular layer is called as ‘hypodermis’. In free living form the hypodermis is composed of number of cells. Whereas in parasitic form hypodermis consist of syncytium with a number of nuclei. Subcuticular layer form a four longitudinal thickening on the inner aspect which are situated on dorsal, ventral and lateral aspect.
Muscular layer: Situated next to subcuticular layer and is divided into 4 quarter by longitudinal thickening.

Last modified: Saturday, 24 September 2011, 4:41 AM

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VPA 211: General Veterinary Parasitology and Helminthology (3+1)

Introduction

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