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The Rhabditids are the interface between the parasitic and free-living nematodes. Most spend their whole life-cycle in soil or other inanimate environments, while some are parasitic on plants (such as the potato eel-worm). A few are facultatively parasitic on animals such as Pelodera, which causes dermatitis in dogs and Halicephalobus, which produces ataxia in horses (and other animals) on rare occasions. There is just one regularly parasitic genus in the superfamily: Strongyloides.


NOTE: do not confuse the terms "Strongyloides" and Strongyloidea!

Strongyloides Species

Humans and domesticated animals each have their own Strongyloides species (e.g. S. westeri in horses, S. ransomi in pigs). Cross-infection between hosts does not seem to be common, although the dog species (which does not occur in the UK) may be zoonotic.

General Appearance

Superficially adult parasitic forms look like trichostrongyloids, the defining morphological features of this super-family are:

  • Very small
  • Non-bursate
  • Small buccal capsule
  • Very long pharynx

General Life-Cycle

The Rhabditoid worms have both free living and parasitic life cycles, making them unique amongst the veterinary nematodes. The parasitic life cycle is direct, infection occurs by ingestion of female L3 larvae from the ground or penetration through the skin. Once ingested the L3 larva moults to L4 and finaly to adult female worms in the small intestine. The free living form of the life cycle produces male and female worms on the ground and can happen for a number of generations without parasitism occuring.

In older animals there can be an accumulation of larvae beneath the skin and in abidominal viscera that are activated at pregnancy and can be passed to the young via the milk from the dam.

Pages in category "Rhabditoidea"

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