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.
A 2-year-old intact male Labrador Retriever dog was presented to a small animal emergency clinic in Sacramento, California, USA with a recent onset of lethargy and inappetence and a single episode of vomiting and bloody diarrhea. Physical examination revealed fever of 105.2°F, enlarged lymph nodes, and dehydration.
After providing supportive care, a centrifugal fecal flotation and fecal sedimentation were performed. Results are shown below.
Figure 1: Centrifugal fecal flotation. 100X magnification
Figure 2: Centrifugal fecal flotation. 400X magnification
Figure 3: Fecal sedimentation. 100X magnification
Figure 4: Fecal sedimentation. 400X magnification
Nanophyetus salmincola eggs
This is a case of “salmon poisoning” caused by Neorickettsia helminthoeca. The rickettsial agent responsible for disease is found within a fluke – Nanophyetus salmincola – that uses salmonid fish as an intermediate host. Dogs and other canids are extremely susceptible to this infection, and disease occurs by consumption of infected raw fish. Disease is most commonly associated with fish in coastal streams of the Pacific Northwest of the USA, including the states of Washington, Oregon, and northern California, and southern Vancouver Island in Canada. The prognosis with appropriate treatment for the N. helminthoeca infection (doxycycline) is good; however, dogs that do not receive appropriate antibiotics will deteriorate quickly and often die.
Note: Although a fecal sedimentation test is preferred to detect fluke eggs, it has been reported that N. salmincola eggs can often be found by a centrifugal fecal flotation test. However, eggs on flotation might be collapsed, folded, or deformed due to the high specific gravity solution (Figures 1 & 2).
Suggested reading: Sykes, J. E., et al. (2010). "Salmon poisoning disease in dogs: 29 cases." JVIM 24(3): 504-513.
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