Which came first the parasite or the egg?
A fecal sample from a 6-month-old, spayed female, Siamese cat was submitted for a gastrointestinal parasite evaluation. The cat did not show any symptoms at submittal. For fecal analysis, a centrifugal fecal flotation with Sheather’s sugar solution (specific gravity, 1.26) was performed, and a low number of these eggs were observed
Image 1: 100X magnification
Image 2: 400X magnification
Demodex spp. eggs.
The fecal sample also showed Demodex spp. adults (Image 3)
Image 3: 200X magnification
Demodex spp. are small wormlike mites with short legs, they live in the hair follicles and sebaceous glands of mammals. Several species of Demodex often parasitize the same animal host, but each species tends to be restricted to a particular location. In cats, dermatitis associated with Demodex cati is rarely noticed and is usually localized on the head and in the ear canals. Demodex gatoi, is a much shorter and is more superficially dwelling than D. cati. Cases of feline demodicosis are believed to be associated with underlying immunosuppressive diseases.
Dropping like flies...
Several backyard poultry farms near the Des Moines river in central Iowa reported numerous deaths among their chickens. One farm lost 17 out of 21 backyard chickens. The referring veterinarian collected and submitted these flies for identification while further diagnostic investigations were being carried out.
These are Simulium flies, which have a characteristic humped appearance. These are small, stout bodied Nematoceran with short antennae having greater than 9 segments (Figure 1). They also have short prominent mouth parts with maxillary palps and distinctive wing venation with large veins crowded towards anterior edge (Figure 2). These flies have been associated with sudden death in backyard poultry flocks and can cause exsanguination and anaphylactic shock in livestock.
Figure 1: Short segmented antennae.
Figure 2: Wing venation.
An unexpected finding...
An apparently healthy shelter kitten was presented for routine ovariohysterectomy. While performing pre-surgical baseline labs the referring veterinarian found this egg on urinalysis. All other lab work was normal and the physical exam was unremarkable.
This is an egg of Pearsonmea, the bladder worm of cats and dogs. Eggs have the typical capillarid appearance being barrel or lemon shaped with two bipolar plugs and a rough shell. Focusing on the shell wall reveals a characteristic thick globular pattern of ridges, as depicted in the image below.
Special thanks to Dr. Jeba Jeba Jesudoss Chelladurai BVSc, MS, DACVM (Parasit) at Iowa State University for providing this case.
Twenty-eight Colorado River toads were confiscated and sent to an exotic veterinary hospital in Oklahoma. At presentation, most of the toads were emaciated with a body condition score of 1-2 out of 5. Fecal samples collected from the colony were sent to a parasitology diagnostic laboratory. A centrifugal fecal flotation with Sheather’s sugar solution was performed (specific gravity, 1.26) and revealed numerous protozoan cysts and a moderate number of larvae (Image 1).
Image 1: Centrifugal fecal flotation 100x magnification
To take a closer look at the larvae, a Baermann test was performed, and a large number of larvae were recovered (Image 2).
Image 2: A large mass of larvae recovered from the Baermann exam.
Image 3: Larvae were approximately 300-500 µm in length with a prominent esophageal bulb 100x magnification
Rhabdias spp. larvae
A Rhabditiform esophagus was clearly observed in these specimens. Rhabdias is a common lungworm of frogs and toads, belonging to the superfamily Rhabditoidea. The life cycle is direct; eggs passed by the parthenogenic female are carried up from the bronchus to the mouth, swallowed, hatched, and passed in the feces as rhabditiform larvae. Frogs and toads become infected by ingestion of infective larvae or by cutaneous penetration. Larvae migrate through the body tissues and become adults in the lungs. Pathologic effects of Rhabdias are unknown. Infections without any pathologic changes are common. Most amphibians are asymptomatic; however, heavy worm burdens may cause lethargy and death. Although Rhabdias have a similar life cycle and morphologic features to Strongyloides stercoralis, they do not infect humans.
Baker, David G. Flynn’s Parasites of Laboratory Animals, Chapter 8, page 146.
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.
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