
Full text loading...
Category: Clinical Microbiology
Histologic Identification of Parasites, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816018/9781555813802_Chap23-1.gif /docserver/preview/fulltext/10.1128/9781555816018/9781555813802_Chap23-2.gifAbstract:
This chapter provides a review of parasite morphology, potential sites in the human host, any recommended special processing or stains, and additional helpful hints. Specific organisms are listed within parasite groups (protozoa, helminths, nematodes, trematodes, cestodes). The chapter also illustrates representative parasitic infections in various body tissues. Identification of parasite adults or immature forms depends on specimen submission and subsequent preparation. If the organisms and tissues are not well preserved, identification may be difficult or impossible. Distinguishing actual organisms from artifact material may also complicate the process. Some general descriptions are provided with diagrams in the chapter to illustrate specific morphologic criteria used for parasite identification. As the protozoa are unicellular organisms with one or more nuclei and various organelles, their simplicity does not require extensive descriptive material. Staining characteristics, nuclear and cytoplasmic stains, and specific stains for carbohydrates are also discussed.
Full text loading...
Entamoeba histolytica. Section of an amebic ulcer of the colon with characteristic undermining and partial destruction of the muscularis. The serosa is edematous and hyperemic. Multiple ulcers may develop and coalesce. Organisms would be found in the healthy tissue border, not in the necrotic material within the ulcer. ×7. (Armed Forces Institute of Pathology photograph.)
Entamoeba histolytica. Section of an amebic ulcer of the colon with erosion of the muscularis. The characteristic “flask-shaped” ulcer, in which the opening on the surface is much smaller than the actual ulcer below, is clearly visible. Multiple ulcers are often present and may coalesce under the surface. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
(Upper) Section of colon shows diffuse invasion of muscularis by trophozoites of Entamoeba histolytica. ×85. (Armed Forces Institute of Pathology photograph; contributed by Ruy Perez-Tamayo, Mexico, D.F.) (Lower) Higher magnification of the same specimen. Trophozoites have infiltrated the muscularis of the colon (arrows). ×170. (Armed Forces Institute of Pathology photograph.)
Entamoeba histolytica. Trophozoite in the exudate within the ulcerated dermis. The nuclear structure is visible but does not clearly show the nucleus and karyosome. The nuclear structure is more darkly staining than the cytoplasm.
Section of colon showing the nuclei and central karyosomes (arrows) of two invading trophozoites of Entamoeba histolytica. ×1,224. (Armed Forces Institute of Pathology photograph.)
Gross image of liver abscess caused by Entamoeba histolytica. Note the sunken area of the abscess. (Centers for Disease Control and Prevention.)
Section of liver at the margin of an amebic abscess showing several Entamoeba histolytica trophozoites (arrows) in addition to necrosis. ×110. (Armed Forces Institute of Pathology photograph.)
Acanthamoeba spp. Cutaneous abscess on arm; nonhealing ulcer, possibly as a result of a human bite wound, that was not recognized as being caused by Acanthamoeba spp. Therapy with routine antibiotics was ineffective. (Courtesy of George Healy, Centers for Disease Control and Prevention.)
Balamuthia mandrillaris. Trophozoites are seen in brain tissue. The organisms are shaped like amebae and have the large, characteristic karyosome. The staining of the karyosome is much darker than that of the cytoplasm of the amebae. (Centers for Disease Control and Prevention.)
Naegleria fowleri. Trophozoites are seen in brain tissue. The organisms are shaped like amebae and have the large, characteristic karyosome. The staining of the karyosome is darker than that of the cytoplasm. The karyosome is not clearly visible in all amebae, and the overall image is not as clear as that in Figure 23.9 . (Centers for Disease Control and Prevention.)
Naegleria fowleri. Trophozoites are seen in brain tissue (1,000× oil immersion). Note the very clearly delineated karyosome within the nucleus. Also note the vacuolated cytoplasm that is sometimes seen at higher magnifications. (Centers for Disease Control and Prevention.)
Giardia lamblia trophozoites seen as very small sickle-like profiles over the intestinal epithelium. ×127. At this magnification, it is very difficult to identify the organisms, but the shape and appearance of the organisms are strongly suggestive of G. lamblia. (Armed Forces Institute of Pathology photograph.)
Giardia lamblia trophozoites seen as teardropshaped organisms. ×645. Although the teardrop shape is visible for some of the trophozoites, the internal structures (nuclei, median bodies, and axonemes) are not visible at this magnification. (Armed Forces Institute of Pathology photograph.)
Giardia lamblia trophozoites seen as teardropshaped organisms; note the two “eyes” (nuclei) looking back at you. At this magnification (1,000× oil immersion), the nuclei, median bodies, and axonemes are visible. Duodenal smear.
Balantidium coli trophozoites within the intestinal wall (arrows). Normally, the ulcers involve the mucosa and submucosa; however, invasion of the muscular layer may occur, as well as bowel wall perforation. Ulcers tend to be flask shaped (like E. histolytica) and shallow and have a wide opening. Extraintestinal dissemination can occur but is rare. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Necrotic gangrenous colon showing Balantidium coli trophozoites in a venule. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of R. B. Holliman.)
Toxoplasma gondii cysts in brain tissue (dark, round objects) of a non-AIDS patient. The presence of these cysts may be an accidental finding at autopsy and may not be the cause of the patient’s illness. ×129. (Armed Forces Institute of Pathology photograph.)
Toxoplasma gondii cyst in brain (note organisms within the cyst); non-AIDS patient. ×645. (Armed Forces Institute of Pathology photograph.)
Toxoplasma gondii cysts in tissue. Some of the organisms appear to be more oval or crescent shaped. While these cysts occur in tissue, their presence may or may not be relevant to the patient’s clinical condition.
Toxoplasma gondii cyst in tissue. In this cyst, the individual organisms can be clearly seen. Cysts in brain tissue tend to be more round than those seen in striated muscle.
Toxoplasma gondii tachyzoites in bone marrow from a 5-year-old child with leukemia. Note the oval or crescent-shaped organisms. (Centers for Disease Control and Prevention.)
Sarcocystis spp. Note the septa which are visible in this low-power image. Bradyzoites of Toxoplasma gondii in striated muscle resemble Sarcocystis spp. However, the Sarcocystis bradyzoites are usually more rounded at both ends, and they are contained in larger cysts than those of Toxoplasma.
The Sarcocystis septa are visible, as are the crescentic spores. The sarcocyst wall varies from thin and smooth to thick and striated. Although sarcocysts may be confused with cysts of Toxoplasma, sarcocysts tend to be larger and contain larger bradyzoites. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Cryptosporidium parasites in the rectum. Note the upper left section with organisms (dark spots) against the brush border. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of K. Lewin.)
Cryptosporidium parasites in the rectum (higher magnification than Figure 23.24 ). Previously, most human cases were diagnosed after examination of small or large bowel biopsy material, often using both light and electron microscopy. However, because biopsy specimens may not originate from the infected area of the mucosa, immunoassays for the detection of antigen in the stool are being widely used. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of K. Lewin.)
Cryptosporidium parasites in the colon. Note the organisms right at the edge of the brush border. The organisms are within parasitophorous vacuoles and hence are enclosed within membranes of host cell origin. The mucosal architecture tends to be abnormal, with marked shortening of the villi and hypertrophy of the crypts. (Centers for Disease Control and Prevention.)
Cryptosporidium spp. Transmission electron microscopy of organisms within parasitophorous vacuoles on the intestinal mucosa. (U.S. Department of Agriculture.)
Cryptosporidium spp. Scanning electron microscopy of organisms at the brush border. Note the sporozoites being released from the cell. (U.S. Department of Agriculture.)
Microsporidia in a corneal lesion; note the periodic acid-Schiff-positive dot at the end of each spore (arrows). Routine histologic testing can be performed by using tissue Gram stains or silver stains. Touch preparations can be methanol fixed and stained with Giemsa stain. Plastic-embedded tissues stained with periodic acid-Schiff, silver, acid-fast, and routine hematoxylin-eosin stains generally stain better than paraffin-embedded tissues. This finding may be related to the use of formalin as a tissue fixative (1,000× oil immersion).
Microsporidia in the intestine; note the spores. When seen in stool, the spores measure approximately 1 to 3 μm. (A) Lower magnification; (B) higher magnification. The microsporidia multiply extensively within the host cell cytoplasm; the life cycle includes repeated divisions by binary fission (merogony) or multiple fission (schizogony) and spore production (sporogony). Both merogony and sporogony can occur in the same cell at the same time. During sporogony, a thick spore wall is formed, providing environmental protection for this infectious stage of the parasite. Microsporidia are characterized by having spores containing a polar tubule, which is an extrusion mechanism for injecting the infective spore contents into host cells. To date, seven genera have been recognized in humans: Brachiola, Encephalitozoon, Enterocytozoon, Pleistophora, Trachipleistophora, Vittaforma, and “Microsporidium,” a catchall genus for those organisms not yet classified.
Microsporidia in various stages of development in the intestinal enterocytes (1,000× oil immersion).
Microsporidia in various stages of development in the intestinal enterocytes. Note the cells that have evacuated their contents into the lumen of the gut (1,000× oil immersion).
Microsporidia. Note the spores within the kidney. Dissemination to the kidneys is not uncommon, particularly with Encephalitozoon spp. Any patient with suspected microsporidiosis should have both stool and urine examined for spores. Both Enterocytozoon bieneusi and Encephalitozoon spp. can disseminate from the gut to other body sites, including the kidneys.
Diagram of roundworm musculature morphology in tissue. (A) Polymyarian type. (B) Meromyarian type. (C) Homomyarian type. C, cuticle; DVC, dorsal-ventral chord; IN, intestine; LA, lateral alae; LC, lateral chord; M, muscle; OV, ovary. See Table 23.8 below. (Illustration by Sharon Belkin.)
Diagram through Loa loa (female on the left, male on the right) (polymyarian type of musculature). Note the well-developed muscle layer divided into four bands separated by the lateral, ventral, and dorsal chords. The muscle cells project into the body cavity. C, cuticle; DVC, dorsal-ventral chord; HY, hypodermis; IN, intestine; LC, lateral chord; M, muscle; SR, seminal receptacle; SV, seminal vesicle; UT, uterus. (Illustration by Sharon Belkin.)
Diagram through Anisakis (left) and Baylisascaris procyonis (right) (polymyarian type of musculature). In Anisakis, note the well-developed muscular esophagus (ES) and the Y-shaped lateral chords (LC). In B. procyonis (brain tissue), one section is through the esophagus (ES) while the other is through the middle of the body, showing the excretory columns (EC), intestine (IN), and large lateral chords (LC). Note that the lateral alae (LA) are visible in each section.
Adult Ascaris lumbricoides in a dilated bile duct. ×12. At this low magnification, the individual polymyarian muscle cells are somewhat more difficult to see but the large lateral chords are clearly visible. (Armed Forces Institute of Pathology photograph.)
Cross section of an Ascaris lumbricoides adult female. The outer cuticle is partially detached from the parasite. The hypodermis and musculature are visible below the cuticle. Central to the musculature, the flattened tube is the gut and the round tubes are reproductive structures. The large round tubes are egg-containing uteri; the others are sections through ovaries and oviducts. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Three transverse sections of Ascaris lumbricoides larvae in the lung, causing bronchopneumonia. ×157. Even in this low-magnification image, the muscle structure (polymyarian) appears to be divided into quadrants by the lateral chords. (Armed Forces Institute of Pathology photograph.)
Baylisascaris procyonis larva (polymyarian type of musculature) and inflammation in the corpus callosum of an infected rabbit. B. procyonis is an ascarid normally found in raccoons, has a normal ascarid-like life cycle, and causes a very serious zoonotic disease in humans. Human infections result from ingestion of eggs that are passed in very large numbers (millions of eggs/day) in the feces of infected raccoons. Rather than developing to adult worms as occurs in the raccoon, the larvae migrate extensively throughout the body tissues, causing visceral larva migrans (VLM) and/or neural larva migrans (NLM). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of K. R. Kozacos.)
Lagochilascaris (polymyarian type of musculature) encapsulated larvae in the submucosa of a resected tonsil. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of D. Botero and M. D. Little.)
Toxocara larva present in the skin. Since these are not photographed from a cross section, the typical musculature arrangement is not visible. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Anisakis in the stomach wall. Note the typical polymyarian type of musculature and the Y-shaped lateral chords. Human infection is acquired by the ingestion of raw, pickled, salted, or smoked saltwater fish. The larvae often penetrate the walls of the digestive tract (frequently the stomach), where they become embedded in eosinophilic granulomas. The throat is occasionally involved. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Dirofilaria sp. Note the polymyarian type of musculature and the clearly delineated lateral chords. Also note the longitudinal ridges in the cuticle (bumpy appearance). (Courtesy of Marjorie R. Fowler and Andrea Linscott.)
Dirofilaria sp. (higher magnification than Figure 23.44 ). Note the typical polymyarian type of musculature and the more clearly delineated longitudinal ridges on the inner surface of the cuticle. The cuticle is relatively thick and multilayered. The very prominent lateral chords are also visible; although ventral and dorsal chords are present, they are usually inconspicuous. (Courtesy of Marjorie R. Fowler and Andrea Linscott.)
Capillaria hepatica eggs in liver. These eggs resemble those of Trichuris trichiura, but the shells in Capillaria eggs are striated. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Diagram through Enterobius vermicularis (both images are of females) (meromyarian type of musculature). Note the very conspicuous lateral alae (LA). The muscle cells (M) are large, of various shapes, and irregular; there are fewer cells per quadrant than seen in the polymyarian type ( Figure 23.35 ). The lateral chords (LC), intestine (IN), ovary (OV), and uterus (UT) are also visible. (Illustration by Sharon Belkin.)
Appendix containing two transverse sections of a female Enterobius vermicularis worm (arrows). ×13. Although this nematode has the meromyarian type of musculature, this magnification is too low to see any details. (Armed Forces Institute of Pathology photograph.)
Cross section of adult Enterobius vermicularis worms in the appendix. Note the characteristic football-shaped eggs (arrows). The lateral alae are also visible. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Colon containing Enterobius vermicularis, non-gravid female, midbody. Note the lateral alae (arrows). ×166. Also note the typical meromyarian musculature, with large, differently shaped, irregular cells (two or three cells in each quadrant). (Armed Forces Institute of Pathology photograph.)
Diagram through Trichuris trichiura (female on the left, male on the right) (homomyarian type of musculature). Note the very small, uniform muscle cells (M) with a regular arrangement, with many cells arranged in a complete circle. Note also the absence of lateral chords. The ejaculatory duct (EJ), intestine (IN), ovary (OV), oviduct (OVD), uterus (UT), and testis (TE) can also be seen. (Illustration by Sharon Belkin.)
Several sections of adult male and female Trichuris trichiura worms in the colon, showing the narrow anterior portion of the worm within the mucosa (“whip”) (arrows) and the thicker posterior portion (“handle”) free in the lumen. ×15. (Armed Forces Institute of Pathology photograph.)
Trichuris trichiura in cross section. Note the smaller sections that represent the head end, which is embedded in the mucosa, while the larger sections represent the tail portion (whip handle).
Trichuris trichiura in the canine cecum. Cross sections through the thin “whiplike” anterior portion and the thick posterior “handle” are seen. Note the musculature of the body wall beneath the cuticle, the gut, and the uterus filled with eggs (arrows). The musculature is of the homomyarian type, with very small, uniform, regular cells with many cells in a complete circle. No lateral chords are present. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Ancylostoma caninum. There are three pairs of teeth in the mouth of this adult hookworm. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Adult Ancylostoma caninum in the canine intestine. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Trichinella spiralis encysted larvae in muscle. Trichinella forms a complex of at least five species, all of which appear to be the same morphologically but, on the basis of DNA studies and comparative features, are quite different. The five recognized Trichinella spp. are T. spiralis, T. nativa, T. nelsoni, T. britovi, and T. pseudospiralis; a sixth species, T. papuae, has also just been proposed. Although Trichinella spp. have the homomyarian type of musculature, the magnification of this image is insufficient to show the details.
Trichinella spiralis encysted larva in muscle. Squash preparation of tissue biopsy specimen.
Diagram of a transverse section of a Taenia proglottid. Under the thick tegument, the underlying parenchyma is divided into cortical (CO) and medullary (ME) layers by a thick band of longitudinal muscles (M). The excretory columns (EC) are clearly visible. Branches of the uterus (UT) and testes (TE) are also seen. (Illustration by Sharon Belkin.)
(Left) Diagram of a cysticercus of Taenia solium. The extensively folded spiral canal and a scolex with two large suckers are clearly visible. The denser tissue of the rostellum (between the two suckers) is also visible. In this particular section plane, the hooklets are not visible. Host tissue forms a fibrous capsule around the cysticercus. (Right) Diagram of a unilocular hydatid cyst of Echinococcus granulosus. The outer thick fibrous wall is visible (FW) and is produced by the host. Within the fibrous layer is the thinner laminated layer (LL), while right below that layer is the thin germinal epithelial layer (GL) from which daughter cysts and multiple protoscolices arise. Multiple protoscolices within a brood capsule are visible in this illustration. Note that the middle laminated layer is acellular and the thin germinal layer contains some calcareous corpuscles. (Illustration by Sharon Belkin.)
Taenia solium cysticercus in pig muscle. The cysticercus consists of a fluid-filled bladder containing a single protoscolex. The cysticerci (T. solium) have a thick bladder wall, and the rostellum has two rows of hooklets (13 each). Each cysticercus measures 5 to 15 mm long by 4 to 12 mm wide. A convoluted spiral canal leads to the rostellum. The parenchyma usually contains calcareous corpuscles. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of P. M. Schantz.)
Taenia solium subcutaneous nodule from a patient. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of K. Juniper, Jr.)
Taenia solium subcutaneous nodule from a patient (higher magnification than Figure 23.62 ). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of K. Juniper, Jr.)
Taenia solium cysticercus. Low magnification.
Taenia solium cysticercus (higher magnification than Figure 23.64 ; same specimen).
Taenia solium cysticercus in the brain, surrounded by fibrous tissue. The scolex is invaginated with two of the four suckers (arrows), and several hooklets are visible. The scolex is surrounded by fluid and the cyst wall. ×42. (Armed Forces Institute of Pathology photograph.)
Scolex of a cysticercus showing a sucker and hooklets of Taenia solium (arrows). ×148. (Armed Forces Institute of Pathology photograph.)
Taenia solium racemose cyst in the brain. Autopsy gross specimen. (From a Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Taenia solium racemose cyst in the brain; the bladder wall of the racemose cysticercus has three separate layers. The tegumental surface has wartlike protuberances and is acidophilic. Beneath the tegument are small, rounded, pyknotic nuclei. The innermost layer is made up of loose connective tissue.
Taenia solium racemose cyst in the brain (higher magnification than Figure 23.69 ; same specimen).
Hymenolepis nana cysticerci in the villi of a mouse. When mature, these cysticerci emerge, attach to the intestinal wall, and develop into the adult worm (same life cycle seen in humans). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of B. Gueft; specimen courtesy of M. Yoeli.)
Hymenolepis nana cysticerci in the villi of a mouse. Note the curved suckers (arrows). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of B. Gueft; specimen courtesy of M. Yoeli.)
Hymenolepis nana cysticerci in the villi of a mouse. Note the hooklets (arrow). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of B. Gueft; specimen courtesy of M. Yoeli.)
Echinococcus granulosus brood capsules (arrow) arising from the germinal layer. The fibrinous wall of the host and the laminated membrane are also seen. ×84. (Armed Forces Institute of Pathology photograph.)
Wall of the Echinococcus granulosus cyst, which has a laminated membrane (arrow). The germinal layer and scolices are also visible. ×35. (Armed Forces Institute of Pathology photograph.)
Echinococcus granulosus, magnification of the protoscolices.
Coenurus from a human eye. Taenia species with multiple scolices; no daughter cysts develop in a coenurus. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of P. J. Fripp.)
Coenurus from a human eye (higher magnification of hooklets than Figure 23.77 ; same specimen). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of P. J. Fripp.)
Coenurus. Note the section through all four suckers. Coenurosis is caused primarily by two species of Taenia, T. multiceps and T. serialis, formerly known as Multiceps multiceps and M. serialis. A coenurus consists of a viscous, fluid-filled bladder into which multiple scolices invaginate. Cysts measure from a few millimeters to a few centimeters in diameter. Protoscolices can number >100, each having four suckers and an armed rostellum. These tend to be much less common than the typical cysticerci caused by T. solium.
Taenia coenurus. Note the sectioned hooklets. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Spirometra sparganum larva in tissue. Spargana are larval forms of various tapeworms in the genus Spirometra. Spargana are white and ribbonlike in shape, range from a few millimeters to >30 cm in length, and are actively motile. The solid sparganum lacks suckers and bladder walls; there are irregular bundles of muscle fibers, typical folded tegument, and calcareous corpuscles in the parenchyma. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Spirometra sparganum larva (higher magnification than Figure 23.81 ; same specimen). Some of the calcareous corpuscles are visible. They appear as small, outlined bodies within the parenchyma. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Diagram of the cross section of a trematode. Note the coiled uterus (UT) containing eggs, the lobed ovary (OV), intestinal ceca (IC), and excretory canals (EC). Also, note the large ventral sucker (VS). (Illustration by Sharon Belkin.)
(Left) Diagram of male and female Schistosoma trematodes. The female worm is lying with the male worm in copulo. Note the small tuberculations on the dorsal tegument of the male worm. (Right) Sections of adult Clonorchis sinensis in the common bile duct. Note that in different sections, different structures are visible, including the intestinal ceca, the ovary, and parts of the testis. Also note the marked proliferation of the bile duct epithelium. (Illustration by Sharon Belkin.)
Two Paragonimus westermani parasites within a lung cavity. Note the dark, small spots of the vitellaria just within the tegument. The dark openings represent the ceca, with clear portions of the uterus. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Paragonimus westermani adult worms in the lung. In this image, the vitellaria are also visible, as are portions of the uterus, the intestinal ceca, and the ventral sucker (seen in the right cross section). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Paragonimus westermani eggs in the lung. Note the granuloma surrounding one of the eggs. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Adult Fasciola hepatica embedded in the intestinal wall. The parasite presents as an oval to round mass limited by a spined cuticle. The parasitic parenchyma is punctuated by multiple sections through the gut. The two centrally located tubular structures, separated by a light-staining muscular sucker (arrow), are part of the reproductive apparatus of the parasite. A marked inflammatory response is present in the adjacent host tissues, and fresh red blood cells can be seen near the parasite. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman; photograph courtesy of B. C. Walton.)
Adult Fasciola hepatica in the liver. Note that the intestinal ceca and portions of the testes are clearly visible. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman; photograph courtesy of B.C. Walton.)
Clonorchis sinensis eggs in the adult worm within the bile duct. Note the operculum that is visible on the egg(s) in the left upper portion of the photograph. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Echinostoma adult worm in the bowel wall. The spines around the oral sucker are seen in cross section. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Schistosoma japonicum eggs in the appendix. The eggs are acid fast. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of I. Miyazaki, Fukuoka, Japan.)
Schistosoma adults in the lung. In the lower left worm cross section, the smaller portion is the female worm; however, it is somewhat difficult to tell that the female worm is lying within the gynecophoral canal of the male. In the right upper section, the male worm is clearly seen. Note that the female worm is not visible in the upper left image and may not be present with the male worm (in copulo). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Schistosoma adults in tissue. Note that the smaller female worm is lying within the gynecophoral canal of the male worm. The intestinal ceca are visible within both male and female worms. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Alaria americana in an autopsied human lung, showing hemorrhagic pneumonia and the etiologic agent, a mesocercaria. Note the evidence of both the oral sucker and the acetabulum (ventral sucker). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of R. S. Freeman.)
Alaria americana (higher magnification than Figure 23.95 ; same specimen). Note the oral sucker at the anterior end. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman. Photograph courtesy of R. S. Freeman.)
Malaria. Section through the cerebrum showing more congestion of the white matter than of the gray. (Armed Forces Institute of Pathology photograph.)
Cerebral malaria showing cerebral capillaries congested with parasitized erythrocytes (arrows). ×269. Parasitized erythrocytes stick to the endothelium and occlude the capillaries. (Armed Forces Institute of Pathology photograph.)
A ring hemorrhage in the brain surrounding a thrombosed vessel. The thrombus contains many parasitized erythrocytes. The erythrocytes in the hemorrhagic area do not contain parasites, a feature which contrasts the low percentage of parasitized erythrocytes in the circulating blood with the high percentage of parasitized erythrocytes in the thrombosed capillaries. ×305. (Armed Forces Institute of Pathology photograph.)
Malarial pigment present in the spleen. The spleen is enlarged to about 500 g during an acute attack and is soft, diffusely pigmented, congested and has rounded edges. The phagocytic cells lining the splenic sinuses contain malarial pigment, free parasites, and parasitized erythrocytes. During an acute attack, malarial pigment is evenly disbursed throughout the spleen.
Cerebral malaria. Note the capillary containing parasitized erythrocytes. In cerebral malaria, the brain is edematous and heavy and has broadened and flattened gyri. Microscopically, the capillaries and small veins are congested and many of the erythrocytes are parasitized. Parasitized erythrocytes stick to the endothelium and occlude the capillaries. Not only are the rings visible, but pigment grains are also seen within the erythrocytes (Armed Forces Institute of Pathology photograph.)
Diagram of amastigotes. (Left) Leishmania donovani amastigotes in a spleen smear. Each amastigote contains the dark, round nucleus and the bar-shaped kinetoplast. When cells are packed with amastigotes, often the complete morphology for each amastigote is not visible. (Right) Trypanosoma cruzi amastigotes in cardiac muscle. Each amastigote contains the nucleus (round, dark) and the kinetoplast (small bar). (Illustration by Sharon Belkin.)
Smear of bone marrow showing many intracellular and extracellular Leishmania organisms. The amastigotes (Leishman-Donovan bodies) appear larger in smears than in tissue sections. The nuclei and kinetoplasts are distinct in these organisms. ×850. In some amastigotes, both the nucleus and kinetoplast (bar) are visible. (Armed Forces Institute of Pathology photograph.)
Leishmania donovani. Section of liver showing dilated sinusoids and greatly enlarged Kupffer cells (arrow). ×140. (Armed Forces Institute of Pathology photograph.)
Enlargement of the Kupffer cell illustrated in Figure 23.104 (arrow). The cytoplasm contains Leishmania organisms. ×1,530. The individual amastigotes are packed into the cell; organism characteristics (nuclei and kinetoplasts) are not clearly visible. The amastigotes appear as very small dots. (Armed Forces Institute of Pathology photograph.)
Wilder’s reticulum stain of the same liver as shown in Figures 23.104 and 23.105 . The small black dots within Kupffer cells are Leishmania organisms. ×374. At this magnification, individual organism characteristics are not visible. (Armed Forces Institute of Pathology photograph.)
Leishmania spp. (cutaneous leishmaniasis). Biopsy specimen taken through the margin of an ulcer showing necrosis, hyperplastic epithelium, and inflammatory cells in the dermis. ×61. (Armed Forces Institute of Pathology photograph.)
Leishmania spp. (cutaneous leishmaniasis). Inflammatory cell infiltrate, which is composed of histiocytes, lymphocytes, and plasma cells. Some of the histiocytes contain amastigotes. ×259. (Armed Forces Institute of Pathology photograph.)
Leishmania spp. (cutaneous leishmaniasis). Reticulum stain showing the nuclei and kinetoplasts (arrows) of the many amastigotes within histiocytes. ×1,530. It is difficult to see the outlines of the actual amastigotes, but the nuclei and kinetoplast are visible in some of the amastigotes within the histiocytes. (Armed Forces Institute of Pathology photograph.)
Trypanosoma cruzi. Chronic chagasic cardiopathy with scarring and chronic inflammation, left ventricle. ×40. (Armed Forces Institute of Pathology photograph.)
Trypanosoma cruzi. Acute chagasic myocarditis with a myofiber filled with amastigotes (arrow). ×400. At this magnification, the amastigotes look like very small dots. (Armed Forces Institute of Pathology. Photograph contributed by the Gorgas Memorial Laboratory.)
Wuchereria bancrofti microfilariae in the epididymis. Note the thin, threadlike structures in the lower right portion of the photograph. Various lengths are seen, depending on the actual tissue cut. Although these helminths are nematodes, they are shown with the blood parasites, since blood is the primary specimen for diagnostic purposes.
Wuchereria bancrofti microfilariae (higher magnification than Figure 23.112 ; same specimen). In this image, the “stringy” microfilariae are easily visible; there is the suggestion of cellular nuclei within the larval worm.
Microfilaria of Wuchereria bancrofti (arrows) in the lung. ×510. In this image the elongated microfilaria is seen and the cellular nuclei within the organism are also visible. (Armed Forces Institute of Pathology photograph.)
Dermis. Longitudinal section of a Loa loa microfilaria within a capillary shows the cephalic space (arrow). ×336. (Armed Forces Institute of Pathology photograph.)
Mansonella streptocerca in a section of skin. Note the long, slender microfilariae in utero. (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Onchocerca volvulus nodule containing adult worms; note the microfilariae in utero (cross sections of the slender microfilariae). (From A Pictorial Presentation of Parasites: A cooperative collection prepared and/or edited by H. Zaiman.)
Microfilariae seen in superficial corneal stroma. ×259. (Armed Forces Institute of Pathology photograph.)
Histologic identification of parasites a
General characteristics of helminths
Staining characteristics
Nuclear and cytoplasmic stains
Carbohydrate stains
Most likely, secondary, and rare body site locations for human protozoan parasites a
Most likely, secondary, and rare body site locations for human helminth parasites a
Musculature of nematodes a