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Acanthocephala (Thorny-Headed Worms): Veterinary Parasitology Guide
Acanthocephala, commonly known as thorny-headed worms, is a phylum of obligate parasitic worms characterized by a retractable proboscis armed with recurved hooks. These parasites primarily inhabit the intestines of vertebrates, including mammals, birds, reptiles, amphibians, and fish.
Acantho means hook, while cephala refers to the head; hence, the members of this phylum are commonly called thorny-headed worms.
The anterior end of the worm possesses a proboscis-like structure, which is armed with recurved hooks.
The proboscis lies within a sac called the proboscis sac. A pair of elongated hollow organs located on either side of the proboscis sac are known as lemnisci. They serve as organs of attachment.
Both the digestive and excretory systems are absent (the excretory function is carried out by clusters of flame cells). The mode of nutrition is saprozoic.
The female has a special organ called the uterine bell, in which the eggs mature. The egg contains a larva called an acanthor.
The life cycle is indirect. The eggs hatch only after they have been ingested by a suitable intermediate host, where the larva develops into a cystacanth, the infective stage. The definitive host becomes infected by ingesting the infected intermediate host.
Important Acanthocephalan Parasites
- Macracanthorhynchus hirudinaceus – Thorny-headed worm of pigs (most important veterinary species).
- Oncicola canis – Intestinal acanthocephalan of dogs and wild carnivores.
- Oncicola felis – Thorny-headed worm of cats and wild felids.
- Prosthenorchis elegans – Important parasite of non-human primates.
- Moniliformis moniliformis – Parasite of rodents; occasionally infects humans and carnivores.
- Neoechinorhynchus rutili – Common acanthocephalan parasite of freshwater fish.
- Pomphorhynchus laevis – Intestinal parasite of freshwater fish.
