The Nematodes

Introduction

Nematodes are commonly called roundworms because, as the name suggests, they are round when viewed in cross section. However, they are in fact cylindrical in structure and taper towards their anterior and posterior ends. They are bilaterally symmetrical, and while the sexes are separate in most species, a few are hermaphrodite. Nematodes that parasitize our domestic animals are found in all parts of the body but are most commonly found in the digestive and respiratory tracts and the circulatory system.

Nematode parasites of domestic animals vary greatly in size ranging from small hair-like worms (up to 2 cm long) in the Superfamily Trichostrongyloidea to large, robust worms ( up to 40cm long) in the Superfamily Ascaridoidea. The following six examples show the considerable variations in size and appearance  seen among the nematodes

Tcanissm.gif (20325 bytes)

heartwormsm.GIF (6682 bytes)

Taxeism.jpg (8551 bytes)

Species:

Toxocara canis

Dirofilaria immitis Trichostrongylus axei
Superfamily:

Ascaridoidea

Filarioidea Trichostrongyloidea
Order: Ascaridida Spirurida Strongylida
Location:

Small intestine

Right heart, pulmonary arteries Abomasum/stomach
Hosts:

Dogs

Dogs, cats, ferrets Ruminants, horses, swine
Size: 10 - 18 cm 23 - 30 cm 0.7 cm
 

SMStrachea.JPG (8842 bytes)

SmCooperia.gif (15165 bytes)

Species:

Parascaris equorum Syngamus trachea Cooperia sp.

Superfamily:

Ascaridoidea Strongyloidea Trichostrongyloidea

Order:

Ascaridida Strongylida Strongylida

Location:

Small intestine Trachea Small intestine

Hosts:

Horses, donkeys Fowl, game birds Ruminants

Size:

15 - 40cm 0.5 - 2 cm 0.45 - 0.9 cm


Rbtn_nex.gif (1502 bytes) Rbtn_cont.gif (1897 bytes) Rbtn_hel.gif (1527 bytes)

 


Parasites and Parasitic Diseases of Domestic Animals
Dr. Colin Johnstone (principal author)
Copyright 1998 University of Pennsylvania
This page was last modified on January 24, 2000