Nematodes trematodes and cestodes handouts

Bio 160 Parasitology

1. Morphologic differences Cestodes (tapeworms)Trematodes (flukes)Nematodes (roundworms)ShapeSegmented planeUnsegmented planeCylindricalBody cavity NoNoPresentBody coveringTegument Tegument Cuticle Digestive tubeNoEnds in cecumEnds in anusSexHermaphroditic Hermaphroditic, except schistosomes which are dioecious Most are dioecious (althpugh a few monoecious species are known). Parthenogenesis also exists in some. Attachment organsSucker or bothridia, and rostellum with hooks (in others no rostellum with hooks) Oral sucker and ventral sucker or acetabulum Lips, teeth, filariform extremities, and dentary platesDifferential Morphology of the Diagnostic Stages of Helminths Found in Humans: Eggs (Nematodes) SpeciesSizeShapeColorStage of Development When PassedSpecific Features And VariationsAscaris lumbricoides fertilized egg60 m x 45 m. Range, 45-70 m x 35-45 m.Round or ovoidal. with thick shell.Brown or yellow brown.1 cell, separated from the shell at both ends.Mammillated albuminous coat or covering on outer shell. Coat is sometimes lost and decorticated eggs have a colorless shell with gray or black internal material. Eggs may be in 2, 4, or more cells, or contain a fully developed larva.unfertilized egg90 m x 40 m. Range, 85-95 m x 35-45 m.Elongated, occasionally triangular, kidney shaped or other bizarre forms. Shell often very thin.
Brown.Internal material is a mass of irregular globules and granules that fills shell.
Mammillated covering attenuated or missing in many cases.
Baylisacaris procyonisLength: 80-85 µm Width: 65-70 µmUsually slightly oval.Brown.Unembryonated.Thick-Shelled with finely pitted outer shell.Toxocara canis75 to 90 µm.Oval or spherical shape.Brown.Unembryonated.With granulated surface and thick-walled. Toxocara cati65 to 70 µm.Oblong or subspherical.Brown.Unembryonated.Thick-shelled and have a pitted surface. Toxascrais leonina75-85 m long x 60-65 m wideUnembryonated.Smooth with a nonpitted shell and the zygote is lighter in color than that of T.canis.Anisakis simplexUnembryonated.Trichuris trichiura54 m x 22 m. Range, 49-65 m x 20-29 m.Elongated, barrel-shaped with a polar "plug" at each end.Yellow to brown. "Plugs" are colorless.1 cell or unsegmented.Polar plugs are distinctive. Eggs occasionally are oriented in a vertical or slanted position and may not be readily recognized. A gentle tap on the coverslip will usually reorient the egg. On rare occasions, atypical eggs lacking polar plugs may be seen.Enterobius vermicularis55 m x 26 m Range, 50-60 m 20-32 m.Elongated, asymmetrical with one side flattened, other side convex.
Colorless.Embryonated. Contains C shaped or tadpole-like embryo. Smooth, thin eggshell with one flattened side. Occasionally may contain a fully developed larva. (More readily found on anal swabs than in feces).Capillaria philippinensisSimilar to T.trichura but are smaller about 45 by 21 m.More oval in shape (sides are more or less straight than convex. Barrel-shaped or peanut-shaped.
Unembryonated.Bipolar mucous plugs are not protruberant. Shell is thick & pitted with radial striations.

2. Capillaria hepaticaAbout 48-66μm x 28-36μm.Unembryonated.Shell of the eggs is striated with shallow polar prominences at either end. Numerous mini-pores can be seen in the outer shell.Trichinella spiralisNo eggs, adult worm gives birth to live larvae (viviparous).Enterobius vermicularis50 to 60 μm by 20 to 30 μm.Elongate-ovoidal, flattened onthe ventral side (“D-shaped).
Colorless.Unembryonated. Will embryonate in 6 hours after laying.Have a thick shell.
Strongyloides stercoralisAbout 52 μm by 58 μm & is similar to that of the hookworm.Small oval thin-shelled bodies.Partially embryonated at the 2-8 cell stage of development.Shell is smooth & thin & the cleavage retracted.
Hookworm Ancylostoma duodenale60 m x 40 m. Range, 57-76 m x 35-47 m.Oval or ellipsoidal with a thin shell.Colorless with grayish cells.4- to 8-cell stage.Occasionally, eggs in advanced cleavage (16 or more cells) or even embryonated may be seen. Rhabditiform larvae may be present if the specimens are old. Species identification can not be made on eggs alone; therefore, eggs should be reported simply as hookworm.Necator americanus65 m x 40 m. Range, 57-76 m x 35-47 m.Necator americanus and Ancylostoma duodenale, the two genera, cannot be distinguished on the basis of their eggs. Culturing of the larvae is required.Differential Morphology of the Diagnostic Stages of Helminths Found in Humans: Larvae RHABDITIFORM LARVA (First Stage. Has bulbed esophagus.)FILARIFORM LARVA (Third Stage. Lacks prominent bulb in esophagus.)SpeciesSizeGenital Primordium Buccal Cavity SizeLength of EsophagusTip of TailStrongyloides stercoralis225 m × 16 m. Range, 200- 300 m × 16-20 m.Prominent. Is an elongate, tapered, or pointed structure located along ventral wall about the body length.
Short, about 1/3-1/2 as long as the width of the anterior end of the body.550 m × 20 m. Range, 500-550 m × 20-24 m.Extends approximately 1/2 length of body.Notched.
Hookworm250 m × 17 m. Range, 200- 300 m × 14-17 m.Inconspicuous. Rarely distinct. When seen, is small, located nearer the tail than that of Strongyloides.
Long. Approximately as long as the width of the body.500 m. Range, 500-700 m × 20-24 m.Extends about 1/4 1ength of body.Pointed.
Differential Morphology of the Adult Stages of Helminths Found in Humans SpeciesMaleFemaleOtherAscaris lumbricoides Males are 2-4mm in diameter and 10-30 cm long. The male posterior end is curved ventrally with two spicules,but no copulatory bursa.
Females are 3- 6mm wide and 20-35cm long. The vulva is located in the anterior end and accounts for about a third of its body length. Uteri may contain up to 27 million eggs at a time with 200,000 being laid per day. The posterior end is straight and conical.
The mouth at the anterior end of both male and female has three finely denticulate lips, one dorsal and two ventro-lateral.
Baylisascaris procyonisAdult worms measure 15 to 20 cm in length and 1 cm in width, tan-white in color, cylindrical and tapered at both ends. They are large stout worms with three lips on the anterior end. Do not have salient cervical alae.Toxocara canisMale worms measure 9–13 by 0.2–0.25 cm. Female worms 10–18 by 0.25–0.3 cm.The adult canis has a round body with spiky cranial and caudal parts, covered by yellow cuticle. The cranial part of the body contains two lateral alae (length 2–3.5 mm, width 0.1 mm).Toxocara catiMay be brownish-yellow to cream

3. colored to pink and may be up to 10cm in length. Adults have short, wide cervical alae giving their anterior ends the distinct appearance of an arrow (hence their name).Toxascaris leoninaHave straight heads, conical tails lacking a protruberance and heavy wingless spicules. Measures 2-7 cm. long.Measures 2-7 mm long.
Anisakis simplexHave a pseudocoel and complete digestive system. The nematode psuedocoel, filled with fluid, functions as a hydrostatic skeleton. possesses three protruding lips around its mouth opening.Trichuris trichiuraMeasures 30 – 45 mm in length. Distinguished from the female by its coiled caudal extremity about 360 degrees or more. A single lanceolate spicule protrudesthrough a refractile penial sheath which has a bulbous termination covered w/ manysmall recurved spines.
Measures 35 – 50 mm in length. Vulva opens at the anterior end of the fleshy portion of the body. Has a single uterus & ovary. Bluntly rounded at the posterior end.
Capillaria philippinensisVery delicate, tiny worms. The male worms measure about 2.3-3.2 mm in length and 23-38 m in width. Small caudal alae. Spineless spicule sheath.
Very delicate, tiny worms. Very delicate, tiny worms. The male worms measure about 2.5-4.3 mm in length and 29-47 m in width. Esophagus is half as long as body. Females usually have eggs in utero which may either be 8-10 eggs arranged in a single row or 40-45 eggs arranged in 2 rows. The female produce eggs & juveniles (larvae) that are passed in the human's feces.Capillaria hepaticaMeasures about 10mm long. has a slightly chitinized spicule within a protrusible membranous sheath.Measures about 20mm long by about 0.1mm wide. Has a protrusible membranous vulvular opening in the esophageal region.Adults are more delicate than Trichuris.
Trichinella spiralisMeasures 1.4-1.6mm in length by 40-60 m in transverse section. Cloaca is found at the caudal end which is evertible during coitus. It is guarded by 2 conspicuous conical papillae which clasp the female during copulation. Spicule is absent. posterior end is curved ventrad.
About 3-4 mm long & 60-80 m in width. vulva opens at the anterior 5th of the body. Has a single uterus which contains larvae. A single ovary is found near the bluntly rounded caudal end.
Enterobius vermicularis2-5 mm long by 0.4 mm in width) with a curved tail and a single spicule (rarely seen)Small, yellowish white female (8-13 mm long by 0.4 mm in width) has a winglike cuticular extension called alae near the mouth, a prominent esophageal bulb and a long pointed tail.Strongyloides stercoralisParasitic malesRhabditoid in type & are almost identical with free-living male.Free-living femalesAre smaller than the parasitic ones & measure 1 mm in length. Short & stout & have a double bulbed muscular esophageal pharynx.Parasitic femalesAre delicate filiform worms, measuring up to 2.2 mm in length. Esophagus occupy 1/3 or 2/5 of the anterior part of the body. Are parthenogenetic, requiring no males in order to produce fertilized & fully embryonated eggs.

4. Free-living malesBroadly fusiform, smaller than the parasitic female with the tail pointed & curved ventrad.HookwormsMales has a conspicuous copulatory bursa.Females have a simple conical tail vulva is postequatorial, 2 ovaries lay several Thousands of eggs a day for 9 years.Grayish white or pinkish with the head slightly bent in relation to the rest of the body. This bend forms a definitive hook shape at the anterior end for which hookworms are named. Stout and anterior end is curved. Buccal capsule is largely and usually armed with cutting plates, teeth, lancets. Lips are reduced or absent.Wuchereria bancroftiThe adult male worm is long & slender, between 4 & 5 cms. in length, a tenth of a cm in diameter, & features a curved tail. The female is 6-10 cms. long, is ovoviviparous (gives birth to microfilariae), & three times larger in diameter than the male. This size deviation can be attributed to the vast numbers of microfilariae that the female produces each day. Posterior end is narrow & abruptly pointed.Brugia malayiMale adult worms (25 mm) are smaller than female worms.Female adult worms (50 mm) are larger than male.Long and threadlike, B. malayi and other nematode possess only longitudinal muscles and move in an S-shape motion. Adults are typically smaller than adult W. bancrofti.Onchocerca volvulusWire-like, filiform & blunt at both ends.Loa loaMales measure 30 to 34 mm in length and 0.35 to 0.43 mm in diameter. Female worms measure 40 to 70 mm in length and 0.5 mm in diameter. Adult worm is thread-like, whitish, and tapers towards the cephalic end with the male having a curved posterior.Dracunculus medinensisMale is half the size of the female adult.Adult female worm measures 50-120 cm by 1 mm. LIFE CYCLES OF NEMATODES
Ascaris lumbricoides

5. Anisakis simplex
Trichuris trichiura

6. Enterobius vermicularis
Strongyloides stercoralis

8. Dracunculus medinensis

9. Differential Morphology of the Diagnostic Stages of Helminths Found in Humans: Eggs (Trematodes) SpeciesSizeShapeColorStage of Development When Passed Specific Features and VariationsSchistosoma mansoni140 m x 66 m. Range, 114-180 m x 45-73 m.
Elongated with prominent lateral spine near posterior end. Anterior end tapered and slightly curved.
Yellow or yellow brown.Embryonated. Contains mature miracidium.Lateral spine. Found in feces; in rare cases, in urine also. Eggs are discharged at irregular intervals and may not be found in every stool specimen. Are rare in chronic stages of infection.
Schistosoma japonicum 90 m x 70 m. Range, 68-100 m x 45-80 m.
Oval. Small lateral spine is often seen or may appear as a small hook or "knob" located in a depression in the shell.
Yellow or yellow brown.Embryonated. Contains mature miracidium.Found in feces. Often coated with debris and may be overlooked.
Schistosoma haematobium143 m x 60 m. Range, 112-170 m x 40-70 m.
Elongated with rounded anterior end and terminal spine at posterior end.Yellow or yellow brown.Embryonated. Contains mature miracidium. In some references- partly mature when laid.
Terminal spine. Found in urine, occasionally in feces. Egg often covered with debris.
Clonorchis sinensis30 m x l6 m. Range, 27-35 m x 11-20 m.
Small, ovoidal, or elongated with broad rounded posterior end and a convex operculum resting on "shoulders" produced by the protruding shell like a lid of a teapot. A small "knob" may be seen on the posterior end.
Yellow brown.Embryonated. Contains mature miracidium.Small size, operculum and "knob" on posterior end. Shell often is covered by adhering debris.
Paragonimus westermani 85 m x 53 m. Range, 68-118 m x 39-67 m.
Ovoidal or elongate with thick shell. Operculum is slightly flattened and fits into shoulder area of shell. Posterior end is thickened. Egg often asymmetrical with one side slightly flattened.
Yellow brown to dark/golden brown.Unembryonated. Found in sputum, occasionally in feces. Resembles egg of D. latum but is larger, slightly asymmetrical and the operculum is smaller and flatter. The widest part of the Paragonimus egg is usually anterior to the center; in a D. latum, the widest area is around the center.
Fasciola hepatica145 m x 80 m. Range, 120-150 m x 63-90 m.
Ellipsoidal, transparent shell with thin double walls. Small, indistinct operculum.
Yellow to light brown.Unembryonated. Contains a larg mass of lecithin granules when freshly voided.Large size. Broadly oval eggs.
Fasciola gigantica160 m x 190 m. Ellipsoidal, transparent shell with thin double walls. Small, indistinct operculum.
Yellow to light brown.Unembryonated. Contains a larg mass of lecithin granules when freshly voided.Large size. Broadly oval eggs.
Fasciolopsis buski140 m x 80 m. Range, 130-159 m x 78-98 m.
Ellipsoidal, clear thick shell. Small, indistinct operculum.Yellow brown.Unembryonated. Filled with yolk cells in which an indistinct germinal cell is imbedded.
Large size. Resembles F. hepatica egg and cannot be easily distinguished from Fasciola.

10. LIFE CYCLES OF TREMATODES
Life cycle of Fasciola hepatica and Fasciola gigantica

11. Differential Morphology of the Diagnostic Stages of Helminths Found in Humans: Eggs (Cestodes) SpeciesSizeShape ColorStage of Development When PassedSpecific Features and VariationsTaenia saginata Taenia solium35 m. Range, 31-43 m.Spherical with thick striated shell.Walnut brown.Embryonated. 6-hooked oncosphere present inside a thick shell.Thick, striated shell. Eggs of T. solium and T. saginata are indistinguishable and species identification should be made from proglottids or scoleces. "Taenia" spp. should be reported if only eggs are found.Taenia pisiformis32-38 m.Round radially striated eggs with hexacanth embryo.Greenish pink.Embryonated. 6-hooked oncosphere present inside a thick shell.Echinococcus granulosus30-43µm in diameter.Small and round, thick-shelled with hexacanth embryo.Embryonated. 6-hooked oncosphere present inside a thick shell.Hymenolepis 72 m. Round or slightly oval. Yellow.Embryonated. 6-hooked Resembles H. nana but

12. diminuta*Range, 70-86 m x 60-80 m.Striated outer membrane and thin inner membrane with slight poles. Space between membranes may appear smooth or faintly granular.
oncosphere inside shell.lacks polar filaments. Poles are rudimentary and often hard to see.
Hymenolepis nana47 m x 37 m. Range, 40-60 m x 30-50 m.
Oval. Shell consists of 2 distinct membranes. On inner membrane are two small "knobs" or poles from which 4 to 8 filaments arise and spread out between the two membranes.
Colorless, almost transparent.Embryonated. 6-hooked oncosphere inside shell.4-8 Polar filaments.
Dipylidium caninum*35-40 m. Range, 31-50 m x 27-48 m.
Spherical or oval. 5-15 eggs (or more) are enclosed in a sac or capsule.Colorless.Embryonated. 6-hooked oncosphere inside shell.Eggs are contained in a sac or capsule which ranges in size from 58 m to 60 m x 170 m. Occasionally capsules are ruptured and eggs are free.Diphyllobothrium latum66 m x 44 m. Range, 58-76 m x 40-51 m.
Oval or ellipsoidal with an inconspicuous operculum at one end and a small "knob" at the other end.Yellow to brown.Unembryonated. Germinal cell is surrounded by a mass of yolk cells which completely fills inner area of shell. Germinal cell is usually not visible.
Egg resembles hookworm egg but has a thicker shell and an operculum.
* Usually found in lower animals, only occasionally found in humans.Differential Morphology of the Larval Stages of Helminths Found in Humans: Tapeworm SpeciesSizeLarval stageSpecific Features and VariationsTaenia solium0.5 cm to 1.5 cm in length and an invaginated scolex.Cysticercus celulosaeFluid filled bladder.Taenia saginata16-20 mm long × 5-7 mm wide.Cysticercus bovisUsually on surface of fecal material. May be single detached proglottids. Each gravid proglottid may contain 80 thousand eggs.Taenia pisiformisCysticercus pisiformisPea sized fluid filled bladder.Echinococcus granulosusGrows to about 5-10 cm within the first year.Bladder-worm or hydatid cystA hydatid cyst can hold as much as 15 liters of fluid and hold millions of infective stages known as hydatid sand.Hymenolepis diminutaCysticercoidLarva has no bladder but instead has a tail. The dark body within the spherical portion is the scolex. The longer the tail, the more mature the cysticercoid.Hymenolepis nanaCysticercoidSpade shaped with the rest of the worm still inside the cyst.Dipylidium caninumCysticercoidDiphyllobothrium latumPlerocercoid can vary in size from 5 mm to 3 cm in length.Procercoid (in the 1st IH) and Plerocercoid in the 2nd IH (sparganum)Plerocercoid has a shallow bothria at the anterior end.
Differential Morphology of the Diagnostic Stages of Helminths Found in Humans: Tapeworm Gravid Proglottids SpeciesSizeAppearance of UterusOtherTaenia soliumIs normally 4 m to 10 m in length, but can become very large, over 12 m long in some situations.
12 mm in length x 5-7 mm wide.Central "stem" or trunk with 7-12 main lateral branches on each side.Usually on surface of fecal material. May be in short chains of 2-3 proglottids. Each gravid proglottid may contain 30-50 thousand eggs. T.solium may contain 800-900 proglottids/adult. Taenia saginataIs normally 2 to 3 m in length, but can become very large, over 50 m long in some situations.
16-20 mm long × 5-7 mm wide.Central "stem" or trunk with 15-30 main lateral branches on each side.Usually on surface of fecal material. May be single detached proglottids. Each gravid proglottid may contain 80 thousand eggs. T.saginata may contain 1-2 thousand proglottids/adult.Taenia pisiformismay reach up to 200 cm in length.

13. Echinococcus granulosusAdult tapeworm ranges in length from 2 mm to 7 mm and has 3 proglottids ("segments") when intact.
Has three proglottids ("segments") when intact — an immature proglottid, mature proglottid and a gravid proglottid.
Hymenolepis diminutaAdult tapeworm measures 20 to 60 cm long.0.7-0.8 mm long × 3-4 mm wide. Broader than long.Uterus not visible. Proglottid filled with eggs.Proglottids usually disintegrate in the intestinal tract and are rarely seen in stools. Egg is usual diagnostic stage.Hymenolepis nanaAdults measure 20 to 60 cm in length.0.2-0.3 mm long x 0.8-0.9 mm wide. Broader than long.Uterus not visible. Proglottid filled with eggs.Proglottids usually disintegrate in the intestinal tract and are rarely seen in stools. Egg is usual diagnostic stage.Dipylidium caninumAdult worms are about 18 inches (46 cm) long.12 mm long × 3 mm wide. Pumpkin-seed shape; tapers at each end.Uterus not visible. Proglottid filled with capsules containing eggs.Proglottids may be passed singly or in chains. Often resemble rice grains in stool.Diphyllobothrium latumIs the longest tapeworm in humans, averaging ten meters long. 2-4 mm long × 10-12 mm wide. Broader than long.Coiled into a rosette appearance.Occasionally, portion of worm may be passed. Egg is usual diagnostic stage. Up to 1,000,000 eggs per day per worm.
Differential Morphology of the Diagnostic Stages of Helminths Found in Humans: Tapeworm Scoleces SpeciesSizeShapeSuckers No.AppearanceOtherTaenia soliumApproximately 1 mm in diameter.Globular or rounded.4Cup-like.Double row of 25-30 large and small brown chitinous hooks arranged around a rostellum (small projection) at the top of the scolex.Taenia saginata1 to 2 mm in diameter.Rounded or slightly pyriform.4Cup-like.Does not have a rostellum or hooks.Taenia pisiformis4Retractable rostellum armed with two rings of rostellar hooks.Echinococcus granulosus4Rostellum is non-retractable and armed with a double crown of 28-50 recurved hooks.Hymenolepis diminuta0.2-0.4 mm in diameter.Globular or club-shaped.4Cup-like.Rudimentary apical rostellum without hooks.Hymenolepis nana0.3 mm in diameter.Globular.4Cup-like.Retractile rostellum with a single row of 20 to 30 hooks.Dipylidium caninum0.35 × 0.37 mm.Rhomboid or rounded.4Oval, cup-like.Prominent conical or ovoid rostellum with 30-150 small thorn-shaped hooks arranged in several rows (1-7 rows). Rostellum may be retracted into a depression at the upper margin of the scolex.Diphyllobothrium latum2 to 3 mm in length × 1 mm wide.Almond-shaped or spatulate.2Grooves.Does not have a rostellum or hooks. Deep grooves (suckers) are located dorsally and centrally on the scolex, but often appear to be lateral.

14. LIFE CYCLES OF CESTODES

15. *Mature cysticercus break out of liver and rest in the peritoneal cavity.
Life cycle of Echinococcus granulosus

16. Hymenolepis nana
Dipylidium caninum
Diphyllobothrium latum