Introduction

Horsehair worms, also known as Gordian worms, are a member of the group Nematomorpha. The hosts of hairworms are mantises and some carnivorous or omnivorous species of Orthoptera and Coleoptera.

Objectives

This report deals with the morphology of the horsehair worm vomited by a domestic dog.

Methods

A 2-year-old, 50-kg, intact male domestic dog was referred because of two times of vomiting. When vomiting, the owner discovered a living worm. We received a worm in living status. The worm was investigated by using light and scanning electron microscopy (SEM) for species determination.

Results

Grossly, the worm was blackish-brown in color and 215 mm in length and 1.2 mm in maximum width. Microscopically, the worm was composed of epicuticle, cuticle, epidermis, muscle, mesenchyme, pseudocoel, nerve cord and gut. But the genital organ was not developed. The SEM study revealed that the cuticle contains five types of elevated structures called areoles. The cuticular surface of the parasite is covered by an abundant type of areoles: simple areole, tubercle areole, bulging areole, crowned areole, circumcluster areole. The observed characteristics of the specimen in this study are the same to those of genus Chordodes.

Conclusions

We concluded that it is a male of Chordodes koreensis belonging to Gordiida. Only nine species of freshwater Nematomorpha are known from Korea, two of which belong to the genus Chordodes. The case of parasitic horsehair worm in dogs has not been recorded, and this is a first gordiosis of dog in Korea.