Breed: Lab/Retriever Mix
Gender: MALE, NEUTERED
The dog presented with vague GI signs of vomiting and inappetence. Imaging studies showed the presence of free abdominal fluid. Approx. 5 ml of fluid was collected and submitted for cytologic exam.
Image 5:Click here for the IDEXX Pathology Report on this case.
The fluid had an increased nucleated count of 15,000 cells/microliter with approximately 85% nondegenerate neutrophils and the remaining 15% of cells were large mononuclear cells and lymphocytes. Several atypical structures consistent with cestode thyridia are noted. These structures often contain clear to yellow refactile structures measuring approximately 20-30 microns are noted. The shapes are variable ranging from oval to angular. These structures are consistent with calcaneous corpuscles.
Calcaneous corpuscles are s which are remnant cells of both larvae and adults forms. They are specific to cestodes and when seen in a cavity effusion are indicative of cestodiasis.
The thyridia are the larval forms of the mesoestode in which the dog is not the definitive host, but rather an abberant host. It’s also thought that some animals may ingest an arthropod which is the first or second intermediate hosts that has been parasitized by the larval stage. These organisms are thought to enter the peritoneum through the intestinal wall. Here they undergo asexual reproduction and eventually incite ascites and inflammation.
This condition, in which the inappropriate larval stage incites peritoneal mesocestodes is expectedly fatal. Even if the patient is currently asymptomatic. Patients with the peritoneal form are not usually shedding cestode ova in the feces.
The metacestode larvae usually exhibit 4 round suckers but both tetrathyridia and acephalic forms are usually present. (These photos do not show obvious suckers.)
Journal of Veterinary Clinical Pathology, Patten et.al, vol.42, issue 1, March 2013, pp. 103-108
Journal of Veterinary Clinical Pathology, Caruso et al, vol. 32, issue 2, June 2003, pp. 50-60
Image 1, above – Mesocestode
Image 4, above
Image 5, above.