Winter is coming
A 1-year-old, intact male bearded dragon was brought to an animal clinic with a history of intermittent soft stool. Centrifugal fecal flotation with Sheather’s sugar solution (specific gravity, 1.25) was performed.
A large number of coccidian oocysts were observed, and the majority of oocysts were already sporulated (Figures 1 and 2).
Morphology of the oocysts was carefully examined; sporulated oocysts contained two sporocysts, and each sporocyst had a small bump or knob like structure on the end (Figures 3 and 4).
Figure 1: Centrifugal fecal flotation 100x magnification.
Figure 2: Several oocysts were already sporulated 400x magnification.
Figure 3: A small knob was observed on each sporocyst (indicated by arrows) 600x magnification.
Figure 4: An additional view at 600x magnification showing the small knob at the end of each sporocyst (indicated by arrows).
The small knob on the end of each sporocyst was a Stieda body. Isospora species with Stieda bodies have been reclassified in the family Eimeriidae, whereas those without Stieda bodies have remained in the family Sarcocystidae. All Isospora species found in mammals lack Stieda bodies, and thus are in the family Sarcocystidae and are named Cystoisospora.
Isospora amphiboluri is a common intestinal coccidian parasite in bearded dragons (Pogona vitticeps). Isospora amphiboluri can damage the intestinal mucosa causing malabsorption, which leads to diarrhea, dehydration, and in severe cases death. Juveniles are most at risk.
Carreno and Barta. (1999). An Eimerid origin of isosporoid coccidia with Stieda bodies as shown by phylogenetic analysis of small subunit ribosomal RNA gene sequences.
Hafeez and Barta. (2019). Conserved mitochondrial genome organization of Isospora species (Eimeriidae, Coccidia, Apicomplexa) infecting reptiles (Pogona vitticeps (Sauria: Agamidae) and birds (Garrulax chinensis Aves: Passeriformes).
Special thanks to Dr. John R. Barta (Professor at Ontario Veterinary College, University of Guelph) for helping and confirming the diagnosis of this case and sharing the references!
How pathogenic is this parasite?
A 4-month-old quarter horse colt was submitted for necropsy. Per submission history, the foal was behaving normally in the pasture the previous morning. Around 3pm, he was down and could not get up. His temperature was >108 °F, and although aggressive supportive care was initiated, the foal was found dead in his stall around 5pm.
No significant gross abnormalities were observed during the necropsy examination. The GI tract contents were watery and muddy, indicating diarrhea. A fecal sample was submitted for a diarrhea panel to determine if there were any viral, bacterial, or parasitic infections.
A centrifugal fecal flotation with Sheather’s sugar solution (specific gravity, 1.26) was performed, and a low number of strongyle type eggs were detected.
Histologic examination of the small intestine revealed a low number of intraepithelial protozoan gamonts (Figure 1).
Figure 1: Histologic examination of small intestine 200x magnification.
The pathologist on the case requested another fecal examination to confirm this protozoan infection. Another centrifugal fecal flotation was performed with saturated sodium nitrate solution (specific gravity, 1.39) and again showed a low number of strongyle eggs and additional protozoan oocysts (arrow) that were not evident on the first fecal flotation (Figures 2 & 3).
Figure 2: Centrifugal fecal flotation with saturated NaNO3 solution (specific gravity, 1.39) 100x magnification.
Figure 3: 200x magnification.
Eimeria leuckarti oocysts
Eimeria leuckarti is an intestinal coccidian parasite common in horses and donkeys. Oocysts are large and ovoid in shape (~ 80 x 60 microns) with a thick dark shell and distinct micropyle. Diagnosis can be challenging. Due to the heavy/dense oocysts, a sedimentation procedure has been recommended, or flotation with a higher specific gravity solution, as in the present case.
Infections appear to have minimal clinical significance in horses; however, it has been incriminated as a cause of intermittent diarrhea. In this case, rotavirus was detected by PCR, which was thought to be the primary cause of severe diarrhea, resulting in sudden death.
Special thanks to Dr. Rory Chia-Ching Chien, DVM, MSc, DACVP for sharing the case and a photo of the histologic examination.
Why did the snake cross the road?
A juvenile, rat snake was brought to a wildlife rescue in Oklahoma after being hit by a car. Due to poor prognosis, the snake was euthanized and sent to necropsy. Necropsy revealed a severe spinal fracture, which most likely occurred during the accident. Also, three partially digested mice were recovered from the gastrointestinal tract. A fecal sample from the snake was sent to the parasitology diagnostic lab, and a centrifugal fecal flotation was performed with Sheather’s sugar solution (specific gravity, 1.25). The following organisms were observed.
Figure 1: 200x magnification
Figure 2: 400x magnification
Psorobia (= Psorergates) simplex mites.
Psorobia simplex is also known as the “follicle mite of mice.” This is a small, round mite, and both adults and nymphs have four pairs of legs. Each tarsus terminates in a pair of simple claws and a pad-like empodium.
Natural hosts for this parasite are mice, although infestation of laboratory mice is now extremely rare. Infestation of mice with P. simplex is characterized by formation of small, distended, white-colored, nodules in the skin. These nodules are thought to form as a result of epidermal growth to accommodate internal pressure of space-occupying mites. All life stages of the mite are found inside these nodules.
In this case, these mites were found in the snake as a spurious parasite – The snake ate the mice, and the mites were just passing through the GI tract of the snake.
Baker. Flynn’s Parasites of Laboratory animals, 2nd ed. Pages 366-367.
Hop to it!
An approximately 6-year-old, intact female, mixed breed rabbit was euthanized after battling with the last stage of uterine adenocarcinoma and brought to necropsy. Besides confirming the adenocarcinoma, gross examination revealed some focal, irregular, depressed areas on the surface of the kidneys. On histologic examination, several spores were observed in the epithelial cells of the kidneys (Figures 1 & 2).
Figure 1: Spores indicated by arrow.
Figure 2: Spores indicated by arrows.
Encephalitozoon cuniculi is a spore-forming pathogen with worldwide distribution and has been isolated from various mammal species such as rabbits, shrews, mice, hamsters, muskrats, guinea pigs, goats, sheep, pigs, horses, domestic dogs, domestic cats, foxes, non-human primates, and man. Historically this pathogen was considered a protozoan parasite; however, due to its unique features, it is currently classified in the phylum Microsporidia. Infection occurs by ingestion or inhalation of spores shed in the feces, mucus, and urine of infected animals. Transplacental transmission has been also reported. Encephalitozoon cuniculi can cause granulomatous lesions in a wide range of tissues, but primarily affects the brain, kidney, or eyes. Most immunocompetent rabbits do not show any clinical signs; however, in some severe cases, granulomatous lesions associated with E. cuniculi can cause vestibular disease, chronic renal failure, lens rupture, pyogranulomatous uveitis, and cataracts.
Ante-mortem diagnosis of E. cuniculi infection is challenging, and the gold standard is post-mortem histologic examination with immunochemical staining. In this case, the E. cuniculi infection was an incidental finding.
Molly Varga, 2014. Textbook of Rabbit Medicine, 2nd ed.
Frank Kunzel, et al. 2018. Clinical signs, diagnosis, and treatment of Encephalitozoon cuniculi infection in rabbit. Veterinary Clinics of North America: Exotic Animal Practice. https://www.sciencedirect.com/science/article/pii/S1094919417302025?via%3Dihub#fig3
Incidental finding or cause of death?
An approximately 8-year-old miniature donkey mare had difficulty foaling. The referring veterinarian provided aggressive supportive therapy but unfortunately the foal and mare did not survive. To determine the cause of death both carcasses were submitted for necropsy.
Grossly, the mare was remarkably emaciated, and there were mild, chronic, multifocal ulcers in the stomach. Histologic examination of the stomach confirmed moderate, chronic-active, multifocal ulcerative gastritis with bacterial infection. Additionally, histologic examination of the mare’s kidney revealed multiple, variable sized parasites in the renal tubular epithelium (Figures 1-3). No abnormalities were detected grossly or microscopically in the foal.
Figure 1: Various parasite stages in the renal epithelial cells (indicated by arrows).
Figure 2: Multiple nuclei lie along the periphery – notice how they look like a flower, these are called “sporoblasts” (indicated by arrow).
Figure 3: Free/Mature sporoblasts (indicated by arrow) – each of these sporoblasts undergoes further divisions to form sporocysts.
Klossiella equi is a protozoan parasite observed in the kidney of equines. The life cycle has not been fully understood; however, it is thought to be a direct life cycle. Sporocysts are passed in the urine and infection takes place by ingestion of sporulated sporocysts. Klossiella equi infection is thought to be fairly common throughout the world but rarely seen.
Klossiella eqi is considered non-pathogenic and usually is not associated with clinical signs. In this case, K. equi infection was an incidental finding, and bacterial translocation from the gastric ulcers and subsequent septicemia was likely related to the death of the mare and foal.
Special thanks to Dr. Rory Chia-Ching Chien, DVM, MSc, Anatomic Pathology Resident at Oklahoma State University, Center for Veterinary Health Sciences for sharing his case and photos!
Taylor MA, Coop RL, Wall RL. Veterinary Parasitology (4thedition).
Gardiner CH, Fayer R. Dubey JP. An Atlas of protozoan parasites in animal tissues.
Ballweber LR, Dailey D, Landolt G. (2012). Klossiella equiInfection in an Immunosuppressed Horse: Evidence of Long-Term Infection. Case Reports in Veterinary Medicine. 2012, 4. doi:10.1155/2012/230398.
Reinemeyer CR, Jacobs RM, Spurlock GN. (1983). A coccidial sporocyst in equine urine. J Am Vet Med Assoc.182(11). 1250–1251.
A fluke finding: is it a fluke egg?!
An approximately 20-year-old, intact male African spurred tortoise was presented to an exotic animal practice with a history of bleeding from the cloaca. Centrifugal fecal flotation with Sheather’s sugar solution (specific gravity, 1.25) and a direct fecal smear with saline solution were performed. A moderate number of large (> 60 µm), brown and yellow/orange colored, oval shaped objects with a cap-like structure on one side (Figures 1 & 2) were observed on the direct fecal smear. Centrifugal fecal flotation revealed many similar looking objects but with a collapsed appearance (Figures 3 & 4).
Figure 1: Direct fecal smear with saline solution. 200X magnification.
Figure 2: Direct fecal smear with saline solution. 600X magnification.
Figure 3: Centrifugal fecal flotation with Sheather’s sugar solution. 400X magnification.
Figure 4: Centrifugal fecal flotation with Sheather’s sugar solution. 400X magnification.
Nyctotherus spp. cysts
Nyctotherus is a large ciliated protozoa commonly found in herbivorous reptiles such as tortoises and some species of lizards. Nyctotherus spp. cysts are often confused with trematode or oxyurid eggs due to the presence of a structure that resembles an operculum on one side. Although uniformly distributed cilia should be apparent on cysts, they are subtle and can be easily overlooked. Nyctotherus is usually harmless, and it was less likely that Nyctotherus caused the cloacal bleeding.
Nyctotherus cysts seem to be fragile, and centrifugal flotation tends to collapse the cysts making it difficult to observe the details of cyst morphology. Direct fecal smear seems to be the best diagnostic test to recover intact Nyctotherus spp. cysts.
Have feedback on the cases or a special case you would like to share? Please email us. We will appropriately credit all submittors for any cases and photos provided.