The Ascaridoidea

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 opening
  • 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 larvae(L2s)
  • 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 definitive hosts
  • Includes species infecting dogs, cats, swine and horses

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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