Retrospective study of spirocercosis in coyotes (Canis latrans) in Costa Rica: epidemiology, pathological findings, and molecular characterization of Spirocerca lupi

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BACKGROUND: Spirocerca lupi is a nematode that infects domestic dogs and wild carnivores. METHODS: This study retrospectively analyzed postmortem records between 1989 and 2024 to assess S. lupi-associated lesions in coyote necropsies. In addition, it conducted molecular characterization of 18S rRNA and cytochrome oxidase subunit 1 (cox1) gene fragments of larvae found at necropsies. Fecal samples from free-ranging coyotes were molecularly examined for S. lupi 18S DNA. RESULTS: Of the 39 coyote cases, 33 (84. 6%) presented S. lupi-associated lesions. A significant association was observed between the presence of Spirocerca nematodes and the development of esophageal granulomas and aortic aneurysms. In addition, an atypical case of spinal cord invasion was documented, representing the first reported occurrence of this condition in coyotes. Out of all fecal samples tested, 4.6% were positive for S. lupi infection. CONCLUSIONS: The obtained cox1 sequence revealed a complete similarity to S. lupi isolated from the Andean fox Lycalopex culpaeus from Peru, suggesting its transmission between wild canid populations. These findings indicate that coyotes play a significant role in S. lupi transmission dynamics and highlight the need for further research on the ecological interactions between domestic and wild canids in Costa Rica.