The order Strongylida includes many of the important nematodes found in
the gastrointestinal tracts of ruminants, horses, and swine, as well as the lungworms of
ruminants and the hookworms of dogs and cats. The following table gives an overview of the
classification of this order with an emphasis on the superfamily Strongyloidea.
| Order |
Superfamily |
Family |
Subfamily |
Genus
- examples |
| Strongylida |
Trichostrongyloidea |
Trichostrongylidae |
|
|
| Dictyocaulidae |
|
|
| Strongyloidea |
Strongylidae |
Strongylinae |
Strongylus |
| Triodontophorus |
| Cyathostominae |
Cyathostomum |
| Cylicostephanus |
| Cylicocyclus |
| Cylicodontophorus |
| Poteriostomum |
| Gyalocephalus |
| Chabertiidae |
Chabertiinae |
Chabertia |
| Oesophagostominae |
Oesophagostomum |
| Syngamidae |
Stephanurinae |
Stephanurus |
| Syngaminae |
Syngamus |
| Ancylostomatoidea |
Ancylostomatidae |
|
|
| Metastrongyloidea |
Metastrongylidae |
|
|
| Protostrongylidae |
|
|
| Filaroididae |
|
|
Their distinguishing features include a copulatory bursa (in males) and a buccal capsule
of variable shape and size. Examples of direct (free living larvae) and indirect
(intermediate host) life cycles can be found among the members of this order.
There are four superfamilies of importance in domestic animals:
- Trichostrongyloidea
- Strongyloidea
- Ancylostomatoidea
- Metastrongyloidea
Females belonging to the superfamilies Trichostrongyloidea, Strongyloidea and
Ancylostomatoidea produce smooth, thin-shelled, ellipsoidal
"strongyle-type" eggs (A), approximately 80-100 microns long
and 40-50 microns wide. One exception to this rule is Nematodirus, whose species produce
eggs that are approximately twice the size of "strongyle-type eggs (B). Notice
the difference between these eggs and the whipworm (Trichuris) egg (C).
A fifth (minor) superfamily, the Diaphanocephaloidea,
are bursate nematodes found in the digestive tracts of terrestrial snakes and occasionally
lizards. There are two genera and thirty three species in this superfamily. Females pass a
"strongyle-type" egg and their life cycles are direct and similar to the
Trichostrongyloidea but it is also believed that paratenic hosts (snails and slugs) may
play a role in their life cycles.
