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Chapter 34 : Artifacts That Can Be Confused with Parasitic Organisms

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Abstract:

Although many body sites and specimens can be examined for the presence of parasites, the most difficult specimen in which to differentiate parasites from artifacts is usually fecal material. Feces consist of a number of components, including (i) undigested food residue; (ii) digestive by-products; (iii) epithelial cells, mucus, and other secretions from the digestive tract; and (iv) many types of microorganisms such as bacteria and yeasts. Considering the ratio between fecal debris and parasites, it is not surprising that many artifacts are responsible for incorrect identifications of protozoan trophozoites and cysts and of helminth eggs and larvae. measures approximately 8 to 10 µm and can be easily confused with other coccidia or artifacts, especially if careful measurements are not taken. Without the use of modified acid-fast stains or immunoassay detection methods, a light infection with coccidia will probably be missed; the more normal the stool consistency, the fewer oocysts and more artifacts will be present. One of the most common errors in examining blood smears is the incorrect identification of platelets as parasites. Any laboratory using staining reagents must use good quality control measures to ensure that the solutions do not become contaminated with artifacts or free-living organisms. The human cells most likely to cause problems with identification are the polymorphonuclear leukocytes (PMNs) and the macrophages. Depending on the stain used, small yeast cells can be confused with coccidian oocysts or microsporidial spores.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34

Key Concept Ranking

Nuclear Membrane
0.69384915
Parasites
0.6395869
Cyclospora cayetanensis
0.6208124
0.69384915
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Figures

Image of Figure 34.1
Figure 34.1

Various structures that may be seen in stool preparations. (Top row) Macrophage (left) and epithelial cells (right) that can be confused with trophozoites. (Second row) Polymorphonuclear leukocyte with a fragmented nucleus (left) and artifact (right) that can be confused with spp. cysts. (Third row) Two artifacts that can resemble protozoan cysts. (Fourth row) Yeast cells (left) and an artifact (right) that can be confused with spp. and , respectively, on positive acid-fast stains; it is important to measure the structures/organisms carefully before confirming organism identification. (Bottom row) Yeast cells (left) that can be confused with microsporidial spores (however, notice the budding cell within the circle), and artifacts (right) that can also be confused with microsporidial spores; these were thought to be bacteria.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.2
Figure 34.2

Fungi parasitizing (A) (or ) sp. within the cytoplasm; (B) sp. within the nucleus.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.3
Figure 34.3

Various structures within the RBC. (A) Malarial “ring” form (early trophozoite); (B) platelet on the RBC surface; (C) Howell-Jolly body; (D) Cabot’s ring. (Illustration by Sharon Belkin.)

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.4
Figure 34.4

(Top row and second row) Stain deposition on the surface of uninfected RBCs that could easily be confused with developing spp. stages. (Third row) gametocytes that have rounded up and no longer appear as the typical crescent-shaped gametocytes that are normally seen (could be due to low temperatures and/or storage for too many hours in EDTA blood). (Fourth row) Developing trophozoites that appear to resemble gametocytes (found on blood smears prepared from EDTA blood that had been collected more than 8 h previously). (Bottom row) RBCs containing Howell-Jolly bodies that could be confused with very small, young ring forms of spp.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.5
Figure 34.5

Exflagellation of microgametocyte; these microgametes could easily be confused with some type of spirochete. These forms were seen in blood films prepared from blood stored for longer than 12 h in EDTA prior to additional smear preparation.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.6
Figure 34.6

(Left) (Right) Note that the amastigotes have the bar while the amastigotes do not; also has the “halo” around the organisms.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.7
Figure 34.7

Artifacts that can resemble microfilariae in wet mounts; these structures are not parasites but instead are some type of threads. Note that there is no internal structure visible.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.8
Figure 34.8

Bronchial epithelium cells. When these cells disintegrate, the ciliary tufts may be visible and may be confused with protozoan flagellates or ciliates (detached ciliary tufts = ciliocytophthoria).

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.9
Figure 34.9

(Top) Root hair. (Middle) Root hair. Note that there is no internal structure visible within the root hairs. (Bottom) rhabditiform larva. Note the short buccal cavity at the head end of the larva and the genital primordial packet of cells within the curved portion of the body.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.10
Figure 34.10

worms. (Upper) Adult worms (called hairworms or horsehair worms), which measure 20 to 50 cm long and are very slender. (Lower) Characteristic structure of worms. (A) Diagram of anterior end; (B) diagram of posterior end of a male worm in the genus ; (C) whole worm. Bar, 1 cm. (Illustration by Sharon Belkin.)

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.11
Figure 34.11

Various artifacts that may be seen in stool preparations (wet mounts or permanent stained smears). Many of these structures are pollen grains or egglike objects. Visually, they can be confused with some of the following helminth eggs: , hookworm, and

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.12
Figure 34.12

Various artifacts that may be seen in stool preparations (wet mounts). Note the egg-like structure in the fourth row (right). There is a small bubble (within the circle) that mimics the small knob found at the abopercular end of a egg.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.13
Figure 34.13

Various types of pollen grains and a root hair. These structures can mimic various helminth eggs (), as well as nematode larvae.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.14
Figure 34.14

(Upper) “Beaver bodies,” which are algae occasionally found in stool; (lower) leaf structure which resembles a trematode. (Courtesy of Joseph Dipersio.)

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.15
Figure 34.15

(Upper) Polymorphonuclear leukocytes. Note the lobed nuclei; if these cells have been in the stool for some time (unpreserved), the nuclei may fragment into four or five pieces, thus resembling multiple nuclei seen in amebic cysts. (Lower) Macrophages. Although these cells often resemble amebic trophozoites, the ratio of nuclear material to cytoplasm is quite different than that seen in actual protozoa.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.16
Figure 34.16

Charcot-Leyden crystals. These crystals are formed from the breakdown products of eosinophils and basophils and may be present in the stool or sputum with or without eosinophils. They tend to stain quite dark on the permanent stained fecal smears, often darker than nuclear material; and although the shape is consistent, there is a large size range in a single fecal smear or sputum mount.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.17
Figure 34.17

Yeast cells in permanent stained fecal smears. Depending on the size and permanent stain used (trichrome, modified acid-fast, modified trichrome), single yeast cells can often be confused with the coccidia or microsporidia.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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Image of Figure 34.18
Figure 34.18

(Upper row) egg (130 to 150 µm by 63 to 90 µm) (left, image is lower magnification than egg) and egg (38 to 45 µm by 22 to 30 µm) (right). (Lower row) eggs (51 to 68 µm by 30 to 35 µm). (Left) Eggs in liver; egg passed in the stool (resembles egg of ). However, note the striated shell of compared with the nonstriated shell seen in a egg.

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
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References

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1. Ashfag-Drewett, R.,, C. Allen, and, R. L. Harrison. 1990. Detached ciliary tufts: comparison with intestinal protozoa and a review of the literature. Am. J. Clin. Pathol. 93:541545.
2. Aw, D. C.,, J. Y. Thong, and, H. L. Chan. 2004. Delusional parasitosis: case series of 8 patients and review of the literature. Ann. Acad. Med. Singapore 33:8994.
3. Beaver, P. C.,, R. C. Jung, and, E. W. Cupp. 1984. Clinical Parasitology, 9th ed. Lea & Febiger, Philadelphia, Pa.
4. Belding, D. L. 1965. Textbook of Parasitology, 3rd ed. Appleton-Century-Crofts, New York, N.Y.
5. Garcia, L. S. 1999. Practical Guide to Diagnostic Parasitology, ASM Press, Washington, D.C.
6. Hadziyannis, E.,, B. Yen-Lieberman,, G. Hall, and, G. W. Procop. 2000. Ciliocytophthoria in clinical virology. Arch. Pathol. Lab. Med. 124:12201223.
7. Isenberg, H. D. 2004. Clinical Microbiology Procedures Handbook. 2nd ed., vol. 1, 2, and 3. ASM Press, Washington, D.C.
8. Leonidas, D. D.,, B. L. Elbert,, Z. Zhou,, H. Leffler,, S. J. Ackerman, and, K. R. Acharya. 1995. Crystal structure of human Charcot-Leyden crystal protein, an eosinophil lysophospholipase, identifies it as a new member of the carbohydrate-binding family of galectins. Structure 3:13791393.
9. Mahoney, C. A.,, N. Sherwood,, E. H. Yap,, T. P. Singleton,, D. J. Whitney, and, P. J. Cornbleet. 1993. Ciliated cell remnants in peritoneal dialysis fluid. Arch. Pathol. Lab. Med. 117:211213.
10. Narumoto, J.,, H. Ueda,, H. Tsuchida,, T. Yamashita,, Y. Kitabayashi, and, K. Fukui. 2006. Regional cerebral blood flow changes in a patient with delusional parasitosis before and after successful treatment with risperidone: a case report. Prog. Neuropsychopharmacol. Biol. Psychiatry 20 Jan. [Epub ahead of print.]
11. Smith, J. W.,, R. M. McQuay,, L. R. Ash,, D. M. Melvin,, T. C. Orihel, and, J. H. Thompson. 1976. Diagnostic Medical Parasitology: Intestinal Protozoa. American Society of Clinical Pathologists, Chicago, Ill.
12. Wenning, M. T.,, L. E. Davy,, G. Catalano, and, M. C. Catalano. 2003. Atypical antipsychotics in the treatment of delusional parasitosis. Ann. Clin. Psychiatry 15:233239.

Tables

Generic image for table
Table 34.1

Artifacts and other confusing cells and organisms

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
Generic image for table
Table 34.2

Artifacts that resemble parasites

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
Generic image for table

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34
Generic image for table

Citation: Garcia L. 2007. Artifacts That Can Be Confused with Parasitic Organisms, p 947-960. In Diagnostic Medical Parasitology, Fifth Edition. ASM Press, Washington, DC. doi: 10.1128/9781555816018.ch34

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