Cytologic Diagnosis of Peritoneal Cestodiasis in Dogs Caused by Mesocestoides sp

Background: Canine peritoneal larval cestodiasis caused by tapeworm larvae of the genus Mesocestoides is an uncommon and possibly fatal disease that can result in ascites and peritonitis. Although abdominal fluid analysis is recommended for dogs with ascites, the cytologic features of Mesocestoides infection have not been described fully. Objective: Our goal was to describe the cytologic features of Mesocestoides larvae and of associated ascitic fluid that was collected from the peritoneal cavity of 4 infected dogs. Methods: Abdominal fluid was obtained from 4 dogs with Mesocestoides sp infection. Gross, chemical, and microscopic evaluations of the fluid were performed using standard techniques. Results: Cytologic findings in 1 dog included intact acephalic metacestodes (larvae without 4 suckers, not tetrathyridia) in various stages of asexual development, whereas fluid from the other 3 dogs contained primarily calcareous corpuscles, remnant tissue specific to cestodes. Abdominal fluid typically was an exudate, with suppuration, hemorrhage, and evidence of necrosis. Total protein concentrations ranged from 2.4 to 5.3 g/dL. Conclusions: Abdominal fluid cytology was useful in the diagnosis of Mesocestoides larval infections in the peritoneal cavity of dogs with ascites. Observation of characteristic calcareous corpuscles or intact metacestodes can provide a defininitive diagnosis of canine peritoneal larval cestodiasis in dogs.