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Dysphagia Secondary to Spirocerca lupi in a German Shepherd Dog

Background: Spirocerca lupi is a nematode that causes nodules in the esophagus and aortic aneurysms in dogs. Animals are infected by eating intermediate host (beetle) containing infective larvae or consuming viscera containing parasitic cysts from paratenic hosts. Dogs commonly have a subclinical presentation, but the most common signs are vomiting and regurgitation. Visualizing nodules or neoplastic masses via esophagoscopy and the presence of S. lupi eggs in feces are the best diagnostic methods. Milbemycin oxime is effective as a treatment for S. lupi. The objective of this study was to describe the diagnostic and medical management of a patient with dysphagia secondary to esophageal S. lupi nodules. Case: A 7-year-old male German shepherd dog was referred for endoscopic examination. The animal presented with chronic severe dysphagia and weight loss with a presumptive diagnosis of an esophageal foreign body. At palpation of the neck, the dog was painful just dorsal to the cricoid cartilage and had submandibular lymphadenomegaly. The animal also exhibited a dropped jaw which could be returned to its normal position by manipulation. Radiographic examination demonstrated a radiopaque image compatible with a mass in the cranial esophagus just caudal to the upper esophageal sphincter. A ﬂuoroscopy study was performed and confrmed the presence of a mass apparently within the esophageal wall preventing the passage of food. Additionally, in this case, small amounts of contrast medium were visualized passing into the dog trachea. The animal was hospitalized exhibiting odynophagia, dysphagia and regurgitation. Blood analysis revealed a hypochromic normocytic anemia, severe thrombocytopenia and hipoalbuminemia. A commercial ELISA test for Ehrlichia spp. and Anaplasma spp. was performed (SNAP 4Dx plus, IDEXX®). The test was positive for Ehrlichia spp. and doxycycline treatment was started. Fluoroscopy was performed using iodinated contrast, and we observed a soft tissue density structure at the ventral wall of the esophagus that was not permitting the passage of the contrast through the upper esophageal sphincter. One week after doxycycline treatment the animal showed a improvement, with appetite and increased weight. In addition, the dropping jaw was no longer evident, but, the dysphagia continued. Laboratory analyses were repeated, and values were within the normal ranges. Esophagoscopy was performed which allowed us to observe a mass suggestive of a nodule secondary to S. lupi. This nodule was found in the cranial esophagus and could not be biopsied. However S. lupi eggs were observed in the fecal study. The patient was treated with milbemycin oxime to which the patient responded favorably, regaining the ability to swallow and gaining weight. Discussion: Spirocercosis is a parasitic disease with a worldwide distribution which occurs mainly in warm climates as in the present case. Dogs often have a subclinical presentation; however when present, the most common clinical signs are regurgitation and vomiting. In the present case the patient had severe chronic dysphagia as the principal sign, which makes this case atypical. Dysphagia occurred in this case because a nodule was formed in the cranial esophagus, which is also rare. This location made it impossible to take endoscopic biopsies, as described by other authors. However, the diagnosis was made by identifying microscopic parasites eggs in the stool test. In addition, dog improved with medical treatment with milbemycin oxime, at the present, no longer shows dysphagia, odynophagia or coughs and has improved their body condition. This is the frst offcial report of the presence of canine Spirocerca lupi in Ciudad Juarez, Mexico. Finally, dysphagia is an uncommon sign in dogs with spirocercosis; however, esophageal nodules secondary to S. lupi should be considered as a cause of this sign. Keywords: endoscopy, milbemycin oxime, Spirocerca lupi, nodule, dysphagia, dog.