Nematodes in the order Ascaridida are relatively large nematodes found in a wide
variety of aquatic and terrestrial vertebrates. In domestic animals there is only
one important superfamily, the Ascaridoidea.
Biological and structural characteristics
- Large nematodes with a predilection for the small intestine.
- Lumen dwellers feeding on gut contents
- Three lips surround the mouth opening
- Serrated ridge or denticle on the inner surface of each lip adjacent to the mouth
- Extremely small buccal capsule
- Tail end of male coiled, lacks a copulatory bursa but may have caudal papillae
- Females lay thick-shelled eggs containing a single cell when passed in host feces
- Direct infection of hosts by ingestion of eggs containing infective second stage
- Life cycles may be direct or indirect and may involve transport hosts in some species
- The parasitic phases of the life cycles usually involve extensive migrations in
- Includes species infecting dogs, cats, swine and horses