Record of occurrence and histopathological changes induced by nematodes of the family Capillariidae in the tongue of fish, reptiles, birds, and mammals.

The family Capillaridae comprises of nematodes within the order Trichinellida that parasitize a wide range of vertebrate hosts, targeting the gastrointestinal, respiratory, and urinary tracts. While these helminths are frequently recorded in scientific literature, few studies report their presence in other anatomical sites such as the tongue. With that in mind, this study provides a systematic review of articles from 1975 to January 2026 focusing on the description of the presence and pathological alterations caused by helminths from the family Capillariidae whose habitat is the tongue of animals A comprehensive search was conducted across multiple databases, including SciELO, PubMed, BVS, Periódico Capes, and ACS publications platforms, using the descriptors "Tongue AND Capillariidae;" "Tongue AND Eucoleus," "Tongue AND Capillaria," and "Histopathology AND Capillariidae". Of the 83 studies initially identified, 18 met the inclusion and exclusion criteria for analysis, and were used in the present study. The review identified 2 genera Eucoleus and Capillaria, parasitizing the tongue. These parasites were found embedded in the stratified squamous keratinized epithelium of the tongue, with adult helminths most frequently localized in the caudal third of the tongue, with eggs being present. In most cases, no significant morphological abnormalities; however, in the case of E. garfiai, was described that showed the presence of adjacent lymphocytic and eosinophilic inflammatory infiltrate, and hyperkeratosis caused by the helminth. Given the limited number of detailed reports, further research is needed to better characterize tissue inflammatory reactions and elucidate the potential clinical and pathological implications of lingual capillariasis.