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Faecal examination

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Abstract

Laboratory-based faecal examinations, especially microscopy for the identification of intestinal parasites, are important in investigating gastrointestinal disease, whereas macroscopic faecal examination is of limited value. This chapter discusses a variety of tests relating to faecal biomarkers, parasites, enteropathogenic bacteria and viruses.

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Figures

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2.3 Faecal parasitology: illustration of comparative egg size of various parasites. (Courtesy of Hoechst-Roussel-Agri Vet Company, USA; permission requested)
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2.4 Faecal parasitology: protozoal parasites. (a) Cyst of sp. in a faecal preparation stained with iodine. Cysts of sp. are 9–13 x 7–9 µm and typically ovoid. Note the four nuclei, two median bodies and intracytoplasmic flagella within the cyst (arrowed). (b) Trophozoite of sp. in a direct faecal smear from an infected dog. Trophozoites are 12–17 x 7–10 µm and are tear-drop-shaped with eight flagella, two nuclei and two median bodies (arrowed). (c) Trichrome-stained trophozoites. Note the undulating membrane (arrowed). (e) cyst (stained). Note the large kidney bean-shaped macronucleus. (f) cyst (not stained). Note the large kidney bean-shaped macronucleus is not easily observed. (g) Oocysts of sp. in a sugar faecal floatation (arrowed). Depending on species, oocysts range from 3.5–7 µm in diameter. (h) Modified Kinyoun’s acid-fast stain of sp. oocysts (arrowed). (i) Oocysts of spp. in a canine faecal float. Note the two different sizes and that several are sporulated. (© The National Center of Veterinary Parasitology at Oklahoma State University, www.ncvetp.org/)
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2.5 Faecal parasitology: tapeworms. (a) Proglottids of are often readily apparent in canine faeces. (b) eggs are found in clusters 120–200 µm in size. Individual eggs measure 35–60 µm in diameter and contain an embryo bearing hooks. (c) Taeniid eggs of spp. and spp. are morphologically indistinguishable, measure 25–40 µm, and consist of a thick, striated wall surrounding a hexacanth embryo. (© The National Center of Veterinary parasitology at Oklahoma State University, www.ncvetp.org/)
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2.6 Faecal parasitology: ascarids. (a) Egg of . The eggs are 85–90 x 75 µm, subspherical and have a thick and pitted shell. (b) Egg of . The eggs are similar to those of , but are 65 x 75 µm and tend to be more elliptical. (c) Egg of . The eggs are approximately 70–80 µm and resemble those of spp., but have a smooth shell and the embryo takes up less space within the egg. (© The National Center of Veterinary Parasitology at Oklahoma State University, www.ncvetp.org/)
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2.7 Faecal parasitology: whipworm. Egg of from an infected dog. Eggs are symmetrical, have plugs at both polar ends, and measure approximately 72–90 x 32–40 µm. (© The National Center of Veterinary Parasitology at Oklahoma State University, www.ncvetp.org/)
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2.8 Faecal parasitology: hookworms. (a) Egg of . Eggs have an elliptical shape, a thin shell and are approximately 52–79 x 28 µm. In fresh faeces, eggs contain morulae, which develop to first-stage larvae within eggs in the environment. (b) Egg of . This hookworm infects dogs (rarely cats) in cooler temperate regions, including the northern USA, Canada and Europe. The eggs resemble those of spp. in that they are elliptical, thin-shelled and contain morulae in fresh faeces, but eggs are slightly larger (71–92 x 35–58 µm). (© The National Center of Veterinary Parasitology at Oklahoma State University, www.ncvetp.org/)
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2.9 Faecal parasitology: larvae. (a) Larva of . Third-stage larvae are approximately 500 µm long and have a tricuspid tail similar to that of the adult female (second- and fourth-stage larvae also have this type of tail). Adults and larvae are found in the stomach of domestic cats and other felids. Diagnosis is based on the identification of larvae or small adults (1 mm) in vomitus using the Baermann test. (b) In fresh faeces, spp. larvae rapidly develop to the infective filariform stage, which enters the host via skin or mucosal penetration. ‘Filariform’ refers to the elongated shape of the oesophagus. In dogs and cats, eggs frequently hatch before leaving the body, thus free larvae are most often found in fresh faeces. (© The National Center of Veterinary Parasitology at Oklahoma State University, www.ncvetp.org/)
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2.10 SNAP immunochromatographic test for in-house testing for infection.
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2.11 SNAP immunochromatographic test for in-house testing for canine parvovirus antigen. After swabbing the sample, the swab tip is placed into the tube. Bending the bulb then breaks the seal and releases conjugate. The bulb is squeezed three times to mix the sample and conjugate, and then squeezed to release five drops into the sample well of the SNAP device.

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