First report of Cylicospirura felineus in a feral domestic shorthair cat in North America

CASE SUMMARY: A feral domestic shorthair cat was euthanized owing to acute onset and progression of neurological signs attributed to ethylene glycol toxicity. At post-mortem examination two nodules were identified within the fundus of the stomach. Examination of the gastric nodules revealed an intact mucosal surface, each with multiple red slender nematodes extending through an individual central pore. Histopathological evaluation of the nodules highlighted unique reactive fibroplasia, mimicking feline gastrointestinal eosinophilic sclerosing fibroplasia (FGESF), encasing numerous nematodes with females possessing gravid uteri containing abundant larvated eggs. The latter findings were highly suggestive of the Cylicospirura genus, further supported by an en face evaluation of the buccal cavity, highlighting a distinctive trifid tooth appearance. Together, these findings are consistent with Cylicospirura felineus. PCR for the COX-1 gene was unsuccessful on formalin-fixed specimens, attributed to nucleic acid and protein crosslinking. RELEVANCE AND NOVEL INFORMATION: This represents the first documented case of Cylicospirura species in a feral domestic shorthair cat in North America. This particular cat lived in the highly urban environment of New Orleans, Louisiana. Identification of this case demonstrates the potential for feral cats to serve as reservoir hosts and ultimately support transmission of Cylicospirura species into domesticated cat populations. Gastric cylicospiruriasis may present clinically as a firm abdominal mass, potentially with a history of chronic vomiting. The latter emphasizes the importance of differentiating this condition from a neoplastic process such as alimentary lymphoma and adenocarcinoma. Histologically, the unique thick anastomosing collagenous cords encasing nematodes represent a stereotypical response observed in a broad array of gastrointestinal inflammation in felines, including intralesional bacteria, fungal hyphae, foreign bodies and, in this case, gastric nematodes that closely resemble FGESF. Additionally, these unique histological lesions have previously been misinterpreted as neoplastic conditions, including sclerosing mast cell tumor and extraosseous osteosarcoma.