Detecting tongue worm in wild dogs and foxes using CT scans

Abstract

Linguatula serrata ("tongue worm") is a zoonotic intranasal parasite found globally in wild dogs, free-ranging dogs, some domestic dogs, and vulpids. Since there are no sensitive tests currently available, infections are underdiagnosed. This is a pilot observational prospective study aimed at determining whether nasal linguatulosis can be diagnosed using CT. The secondary aims were to evaluate radiography, rhinoscopy, and nasal egg swabs as methods in the diagnosis of tongue worms. Fifty-four wild canids and three vulpids euthanased by gunshot were sourced from pest-control officers. Cadaver heads were subjected to helical CT examination, nasal-swabbed for tongue worm eggs, and necropsied. Radiographs and rhinoscopy were performed on cadavers suspected to be infected based on preliminary CT examination. Tongue worms were retrieved at necropsy in 25 dogs and one fox. CT findings in animals with no nasal cavity ballistic damage were reviewed in six infected dogs and one infected fox. Adult female tongue worms were identified in 4 of 6 dogs and 1 of 1 fox as long, tubular, slightly heterogeneously attenuating structures in the mid to caudal nasal cavities. They were not clearly visible in CT scans when surrounded by nasal fluid, and small parasites (male and immature females) were not discernible. Radiographic findings were mild and nonspecific. One tongue worm was detected in 1 of 12 dogs examined rhinoscopically. Tongue worm eggs were found in swabs from 7 of 25 dogs. While small tongue worms could not be detected with CT, CT proved to be a useful diagnostic method for visualizing adult female tongue worms.