Ever seen a tongue worm?

VRU 2024

January 21, 2025

Alice Birckhead, David Jenkins, Shokoofeh Shamsi, et al.

Background
Linguatula serrata (tongue worm) is a zoonotic intranasal parasite in canids and vulpids, associated with nonspecific signs of rhinitis. Due to limited diagnostic methods, infections are underreported. This pilot study aimed to evaluate the efficacy of computed tomography (CT) for detecting nasal linguatulosis in wild canids and vulpids, and to compare CT with radiography, rhinoscopy, and nasal egg swabs.

Methods
The study included 54 wild canids and 3 vulpids euthanized via pest control. Cadaver heads underwent CT scanning, rhinoscopy, nasal swabbing, and necropsy. Tongue worms were identified through imaging and necropsy. The CT findings were compared to radiographs and other diagnostic methods. Parasite characteristics such as location, size, and attenuation values were recorded, and nasal swabs were analyzed for eggs using flotation.

Results
-CT identified adult female tongue worms in 4 of 6 infected dogs and 1 fox with intact nasal cavities. Smaller male worms and immature females were not detectable.
-Female tongue worms were long, tubular structures with heterogenous attenuation (66–492 HU) and a thin mineralized rim, often seen in the mid to caudal nasal cavities.
-Necropsy confirmed infection in 25/54 dogs and 1/3 foxes, retrieving 128 parasites (49 females, 79 males). Only 7 of 25 infected dogs had positive nasal swabs.
-Rhinoscopy visualized tongue worms in only 1 of 12 infected dogs. Radiographs provided minimal diagnostic value.

Limitations
-The study used cadavers, limiting live-patient applicability. Postmortem changes and freezing-thawing may have influenced results.
-Male worms and immature females were undetectable on CT due to their small size and border effacement with nasal fluid.
-Ballistic damage in some specimens further hindered imaging analysis.

Conclusions
CT is a useful tool for detecting adult female Linguatula serrata in nasal cavities, offering diagnostic advantages over rhinoscopy and nasal swabs. However, its inability to detect male worms and immature females means it cannot fully rule out infection. Further research in live animals is recommended to refine diagnostic protocols and assess associated pathology.

Sagittal (A), dorsal (B), and transverse (C) bone window CT images of the head, with the image axis aligned with the dorsal aspect of the frontal bone/body of the tongue worm. White arrows point to the female tongueworm. Note: A second female tongue worm is partially visible in the right nasal cavity in B and C. D, Female tongue worm photographed in situ (white arrows) in the same dog, following removal of the nasal turbinates. Note: The tongue worm had been pulled with forceps slightly rostrally and ventrally prior to the photograph, and the photograph was flipped to the orientation of the sagittal CT image

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