Esophageal spirocercosis with pulmonary egg deposition and secondary hypertrophic osteopathy in a dog from Costa Rica

Highlights

• First report of active spirocercosis in Costa Rica and Central America.

• Dog with esophageal spirocercosis accompanied with pulmonary egg deposition.

• Hypertrophic osteopathy in four limbs resolved with treatment.

Abstract

Spirocerca lupi is the etiologic agent of spirocercosis in canids from the tropical and subtropical regions of the world. A 1-year-old dog was presented with weight loss and diarrhea. Upon examination, thickened limbs, a mass in the lung's right middle lobe and an esophageal mass were found. The pulmonary mass aspirate revealed S. lupi eggs surrounded by a purulent infiltrate. Limb bone biopsies showed irregular mineralization and cartilaginous metaplasia. Treatment with doramectin resolved the initial clinical signs. However, regurgitation was reported 5 months later. Therefore, the dog received additional doramectin and later vomited a worm morphologically consistent with a S. lupi adult. Herein we report the esophageal migration of S. lupi with egg deposition to the lung parenchyma, accompanied by secondary hypertrophic osteopathy. This report highlights the presence of S. lupi in Costa Rica and the importance of including this parasite as a differential diagnosis when compatible signs are identified.

Introduction

Spirocerca lupi is the etiologic agent of spirocercosis in canids from tropical and subtropical regions around the world (Rojas et al., 2020). It has an indirect life cycle, with dung beetles (Insecta: Coleoptera) as intermediate hosts and canids, usually domestic dogs, as definitive hosts. Dogs become infected by ingesting dung beetles carrying L3 larvae, which are then released in the stomach and start their migration through the walls of the epiploic gastric arteries of the dog until they reach the aorta, where the L3 molt to L4 pre-adults. Approximately 3 months after infection, the worms reach the esophagus, their final niche in the dog, where they start developing into sexually mature adults. Aberrant migrations to thoracic (Harrus et al., 1996), nervous (Chai et al., 2018; Ruggeri et al., 2019), cutaneous (Singh et al., 1999) and urinary organs (Thanikachalam et al., 1984) have been documented.

The most common presentation of spirocercosis includes esophageal nodules which can be classified as non-neoplastic or neoplastic according to the cell inflammatory infiltrate, differentiation of tissue resident cells and external appearance of the nodules (Rojas et al., 2020). Approximately 25% of the esophageal nodules undergo malignant transformation to osteosarcoma, fibrosarcoma, undifferentiated sarcoma (Dvir et al., 2011; Ranen et al., 2004) or chondrosarcoma (Wijekoon et al., 2018), all of them with poor prognosis in the infected animal. Furthermore, spirocercosis has been associated with dyspnea, dysphagia, vomiting and regurgitation (Mazaki-Tovi et al., 2002). In addition, the formation of aortic aneurysm scars, as well as thoracic vertebrae spondylitis and osteoproliferative abnormalities in distant sites can also occur (Rojas et al., 2020).

Spirocercosis has been reported in many countries around the world, but scarce information is available from Latin America (Chikweto et al., 2012; Rodriguez-Vivas et al., 2019; Santisteban-Arenas and Piedrahita, 2016). In Costa Rica, S. lupi has been previously described in retrospective clinical series (Berrocal and Martin, 2000) and in a coprological study (Valverde, 2010), but has never been reported as an active case. In the present report, we provide further evidence of the circulation of S. lupi in dog populations of urban areas of Costa Rica.