Spirurida

Definition

An order of parasitic nematodes (roundworms) in the class Chromadorea, characterized by complex life cycles typically involving arthropod intermediate hosts. Members possess elongated, unsegmented, cylindrical bodies lacking circulatory and respiratory systems. The order includes families of significant medical and veterinary importance such as Onchocercidae (filarial worms), Gnathostomatidae, and Thelaziidae. Many spiruridans are transmitted to vertebrate definitive hosts through the bites of blood-feeding insects or via ingestion of infected arthropods.

Etymology

From Latin spīra ("coil, twist") + Ancient Greek ourá ("tail") + -ida (taxonomic suffix), referring to the twisted or coiled tail morphology characteristic of many members.

Example

The eyeworm Thelazia callipaeda (family Thelaziidae, order Spirurida) uses muscid flies as intermediate and definitive hosts; adult worms reside in the conjunctival sacs of carnivores and humans, with larvae developing in the fly's digestive tract before transmission occurs via face-feeding behavior.

Synonyms

• Spiruromorpha (former superorder)

Related Terms

• Nematoda
• Chromadorea
• Rhabditida
• Onchocercidae
• Filarioidea
• vector-borne parasite
• intermediate host
• definitive host
• arthropod-borne disease

Usage Notes

Taxonomic placement has been revised: Spirurida was formerly treated as an order within class Secernentea, but current classification places it as an order within Chromadorea (subclass Plectia, superorder Rhabditica). The term Spirurida should not be confused with Spiruridae (a family within the order) or Spirurina (a suborder). Many spiruridan parasites are of economic importance in livestock and companion animals, with control strategies often targeting the arthropod vectors.