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Category: Clinical Microbiology
Less Common Helminths, Page 1 of 2
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There are a wide variety of less commonly encountered helminthic parasites, which may be nematodes, cestodes, or trematodes. The diseases caused by these parasites are interesting and demonstrate their highly evolved life cycles and the complex interactions with their hosts. These diseases range from subclinical, e.g., dipylidiasis, to possibly life-threatening, e.g., baylisascariasis. In many instances, the disease occurs only in a particular geographic area, which is largely determined by the biological ranges of the definitive and intermediate hosts. Dietary customs are also important in the prevalence of human disease, as many of these are associated with the ingestion of raw animal products. The treatment of these parasites varies depending on the infectious agent, but common preventive measures may significantly diminish the transmission of many of these parasitic diseases. These measures include the zoonotic control of parasitic disease in animal hosts and the vectors of transmission, washing of fruits and vegetables, access to clean drinking water, and thorough cooking of meats before consumption.
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(top row, left) This Anisakis species (arrows) has penetrated into the deep tissues of the abdomen. Multiple cross sections of the worm, which is 300 μm in diameter, are seen in the omentum. Movat’s stain; original magnification, ×2.5. doi:10.1128/9781555817381.ch147.f1
(top row, left) This Anisakis species (arrows) has penetrated into the deep tissues of the abdomen. Multiple cross sections of the worm, which is 300 μm in diameter, are seen in the omentum. Movat’s stain; original magnification, ×2.5. doi:10.1128/9781555817381.ch147.f1
(top row, right) This coiled first-stage T. spiralis larva is in a “nurse cell.” Note the hyaline, amorphous appearance of the external aspect of the nurse cell and the surrounding chronic inflammatory infiltrate. The worm diameter is 35 μm. Hematoxylin and eosin stain; original magnification, ×30. doi:10.1128/9781555817381.ch147.f2
(top row, right) This coiled first-stage T. spiralis larva is in a “nurse cell.” Note the hyaline, amorphous appearance of the external aspect of the nurse cell and the surrounding chronic inflammatory infiltrate. The worm diameter is 35 μm. Hematoxylin and eosin stain; original magnification, ×30. doi:10.1128/9781555817381.ch147.f2
(middle row, left) The minute lateral alae are useful in the identification of Toxocara species. The worm diameter is 18 μm. Hematoxylin and eosin stain; original magnification, ×500. doi:10.1128/9781555817381.ch147.f3
(middle row, left) The minute lateral alae are useful in the identification of Toxocara species. The worm diameter is 18 μm. Hematoxylin and eosin stain; original magnification, ×500. doi:10.1128/9781555817381.ch147.f3
(middle row, right) The serpiginous tract of a female D. medinensis worm is demonstrated in the scrotum of this patient. doi:10.1128/9781555817381.ch147.f4
(middle row, right) The serpiginous tract of a female D. medinensis worm is demonstrated in the scrotum of this patient. doi:10.1128/9781555817381.ch147.f4
(bottom row, left) Rhabditiform larvae (short arrow) fill the body cavity of this gravid D. medinensis worm. Also note the presence of the two prominent bands of somatic muscle (long arrow). The worm diameter is 1.1 mm. Movat’s stain; original magnification, ×25. doi:10.1128/9781555817381.ch147.f5
(bottom row, left) Rhabditiform larvae (short arrow) fill the body cavity of this gravid D. medinensis worm. Also note the presence of the two prominent bands of somatic muscle (long arrow). The worm diameter is 1.1 mm. Movat’s stain; original magnification, ×25. doi:10.1128/9781555817381.ch147.f5
(bottom row, right) The bipolar plugs (arrows), pitted eggshell, and rectangular shape are characteristic of Capillaria species. This photomicrograph is from a human small intestine and demonstrates an egg that is 40 μm long. Hematoxylin and eosin stain; original magnification, ×490. doi:10.1128/9781555817381.ch147.f6
(bottom row, right) The bipolar plugs (arrows), pitted eggshell, and rectangular shape are characteristic of Capillaria species. This photomicrograph is from a human small intestine and demonstrates an egg that is 40 μm long. Hematoxylin and eosin stain; original magnification, ×490. doi:10.1128/9781555817381.ch147.f6
(row 1, left) The immature P. cantonensis worm (arrows) in the meninges of this patient is eliciting a marked eosinophilic response. The worm is 200 μm in diameter. Hematoxylin and eosin stain; original magnification, ×50 (AFIP negative no. 73-6862). doi:10.1128/9781555817381.ch147.f7
(row 1, left) The immature P. cantonensis worm (arrows) in the meninges of this patient is eliciting a marked eosinophilic response. The worm is 200 μm in diameter. Hematoxylin and eosin stain; original magnification, ×50 (AFIP negative no. 73-6862). doi:10.1128/9781555817381.ch147.f7
(row 1, right) The coiled remnants of an immature male D. immitis worm are present in this branch of the pulmonary artery. The maximum worm diameter is 250 μm. Movat’s stain; original magnification, ×15 (AFIP negative no. 71-11563). doi:10.1128/9781555817381.ch147.f8
(row 1, right) The coiled remnants of an immature male D. immitis worm are present in this branch of the pulmonary artery. The maximum worm diameter is 250 μm. Movat’s stain; original magnification, ×15 (AFIP negative no. 71-11563). doi:10.1128/9781555817381.ch147.f8
(row 2, left) The two uteri (arrows), muscle, and trilaminar (arrowhead), smooth cuticle are characteristic of an immature female D. immitis worm. The worm diameter is 250 μm. Movat’s stain; original magnification, ×80 (AFIP negative no. 72-2732). doi:10.1128/9781555817381.ch147.f9
(row 2, left) The two uteri (arrows), muscle, and trilaminar (arrowhead), smooth cuticle are characteristic of an immature female D. immitis worm. The worm diameter is 250 μm. Movat’s stain; original magnification, ×80 (AFIP negative no. 72-2732). doi:10.1128/9781555817381.ch147.f9
(row 2, right) The Dirofilaria species other than D. immitis have external longitudinal cuticular ridges, whereas the cuticle of D. immitis is smooth. Dirofilaria tenuis is pictured here, in cross section; it is 270 μm in diameter and has obvious cuticular ridges (arrows). Dirofilaria species other than D. immitis are often found in a subcutaneous location rather than in the pulmonary arterial vasculature. Movat’s stain; original magnification, ×80 (AFIP negative no. 94-5122). doi:10.1128/9781555817381.ch147.f10
(row 2, right) The Dirofilaria species other than D. immitis have external longitudinal cuticular ridges, whereas the cuticle of D. immitis is smooth. Dirofilaria tenuis is pictured here, in cross section; it is 270 μm in diameter and has obvious cuticular ridges (arrows). Dirofilaria species other than D. immitis are often found in a subcutaneous location rather than in the pulmonary arterial vasculature. Movat’s stain; original magnification, ×80 (AFIP negative no. 94-5122). doi:10.1128/9781555817381.ch147.f10
(row 3, left) An egg packet of D. caninum, obtained from a crushed gravid proglottid, is 150 μm in diameter. The eggs within the packet are 40 μm in diameter. Unstained (AFIP negative no. 86-7369). doi:10.1128/9781555817381.ch147.f11
(row 3, left) An egg packet of D. caninum, obtained from a crushed gravid proglottid, is 150 μm in diameter. The eggs within the packet are 40 μm in diameter. Unstained (AFIP negative no. 86-7369). doi:10.1128/9781555817381.ch147.f11
(row 3, right) The thick inner membrane of the egg of Hymenolepis diminuta is surrounded by a gelatinous matrix and then by an outer striated shell. The eggs of H. diminuta are spherical, whereas those of Hymenolepis nana are ovoid. The egg pictured here is 80 μm in diameter. Unstained; original magnification, ×250 (AFIP negative no. 96-5119). See chapter 143 for more-detailed coverage of Hymenolepis spp. doi:10.1128/9781555817381.ch147.f12
(row 3, right) The thick inner membrane of the egg of Hymenolepis diminuta is surrounded by a gelatinous matrix and then by an outer striated shell. The eggs of H. diminuta are spherical, whereas those of Hymenolepis nana are ovoid. The egg pictured here is 80 μm in diameter. Unstained; original magnification, ×250 (AFIP negative no. 96-5119). See chapter 143 for more-detailed coverage of Hymenolepis spp. doi:10.1128/9781555817381.ch147.f12
(row 4, left) A sparganum superficially resembles an adult tapeworm. Close inspection, however, clarifies its immature form, with a head with only a ventral groove or bothrium (arrow) and a lack of proglottids. The maximum width is 6 mm. Unstained; original magnification, ×0.5 (AFIP negative no. 70-15303). doi:10.1128/9781555817381.ch147.f13
(row 4, left) A sparganum superficially resembles an adult tapeworm. Close inspection, however, clarifies its immature form, with a head with only a ventral groove or bothrium (arrow) and a lack of proglottids. The maximum width is 6 mm. Unstained; original magnification, ×0.5 (AFIP negative no. 70-15303). doi:10.1128/9781555817381.ch147.f13
Other less common nematodes
Other less common nematodes
Other less common cestodes a