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Editor's Notes

1. Eggs of Hymenolepisdiminuta.  These eggs are round or slightly oval, size 70 - 85 µm X 60 - 80 µm, with a striated outer membrane and a thin inner membrane. The space between the membranes is smooth or faintly granular.  The oncosphere has six hooks.  There are no polar filaments extending into the space between the oncosphere and the outer shell.
2. Trichurishe unembryonated eggs are passed with the stool .  In the soil, the eggs develop into a 2-cell stage , an advanced cleavage stage , and then they embryonate ; eggs become infective in 15 to 30 days.  After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae  that mature and establish themselves as adults in the colon .  The adult worms (approximately 4 cm in length) live in the cecum and ascending colon.  The adult worms are fixed in that location, with the anterior portions threaded into the mucosa.  The females begin to oviposit 60 to 70 days after infection.  Female worms in the cecum shed between 3,000 and 20,000 eggs per day.  The life span of the adults is about 1 year.
3. D.latum
4. Dipylidiumcaninum egg packetsGravid proglottids are passed intact in the feces or emerge from the perianal region of the host .  Subsequently they release typical egg packets .  On rare occasions, proglottids rupture and egg packets are seen in stool samples.  Following ingestion of an egg by the intermediate host (larval stages of the dog or cat flea Ctenocephalidesspp.), an oncosphere is released into the flea's intestine.  The oncosphere penetrates the intestinal wall, invades the insect's hemocoel (body cavity), and develops into a cysticercoid larva .  The larva develops into an adult, and the adult flea harbours the infective cysticercoid .  The vertebrate host becomes infected by ingesting the adult flea containing the cysticercoid .  The dog is the principal definitive host for Dipylidiumcaninum.  Other potential hosts include cats, foxes, and humans (mostly children) , .  Humans acquire infection by ingesting the cysticercoid contaminated flea.  This can be promulgated by close contact between children and their infected pets.  In the small intestine of the vertebrate host the cysticercoid develops into the adult tapeworm which reaches maturity about 1 month after infection .  The adult tapeworms (measuring up to 60 cm in length and 3 mm in width) reside in the small intestine of the host, where they each attach by their scolex.  They produce proglottids (or segments) which have two genital pores (hence the name "double-pored" tapeworm).  The proglottids mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool .
5. Hookworm eggs in unstained wet mounts, taken at 400× magnificationCausal Agents:The human hookworms include the nematode species, Ancylostomaduodenale and Necatoramericanus.  A larger group of hookworms infecting animals can invade and parasitize humans (A. ceylanicum) or can penetrate the human skin (causing cutaneous larva migrans), but do not develop any further (A. braziliense, A. caninum, Uncinariastenocephala).  Occasionally A. caninum larvae may migrate to the human intestine, causing eosinophilic enteritis.  Ancylostoma caninum larvae have also been implicated as a cause of diffuse unilateral subacuteneuroretinitis.Life Cycle (intestinal hookworm infection):Eggs are passed in the stool , and under favorable conditions (moisture, warmth, shade), larvae hatch in 1 to 2 days.  The released rhabditiform larvae grow in the feces and/or the soil , and after 5 to 10 days (and two molts) they become filariform (third-stage) larvae that are infective .  These infective larvae can survive 3 to 4 weeks in favorable environmental conditions.  On contact with the human host, the larvae penetrate the skin and are carried through the blood vessels to the heart and then to the lungs.  They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed .  The larvae reach the small intestine, where they reside and mature into adults.  Adult worms live in the lumen of the small intestine, where they attach to the intestinal wall with resultant blood loss by the host .  Most adult worms are eliminated in 1 to 2 years, but the longevity may reach several years.Some A. duodenale larvae, following penetration of the host skin, can become dormant (in the intestine or muscle).  In addition, infection by A. duodenale may probably also occur by the oral and transmammary route.  N. americanus, however, requires a transpulmonary migration phase.
6. The eggs of Taeniasolium and T. saginata are indistinguishable from each other, as well as from other members of the Taeniidae. The eggs measure 30-35 micrometers in diameter and are radially-striated. The internal oncosphere contains six refractile hooks.Life cycle of Taeniasaginata and Taeniasolium Taeniasis is the infection of humans with the adult tapeworm of Taeniasaginata or Taeniasolium.  Humans are the only definitive hosts for T. saginata and T. solium.  Eggs or gravid proglottids are passed with feces ; the eggs can survive for days to months in the environment.  Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated with eggs or gravid proglottids .  In the animal's intestine, the oncospheres hatch , invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci.  A cysticercus can survive for several years in the animal.  Humans become infected by ingesting raw or undercooked infected meat .  In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years.  The adult tapeworms attach to the small intestine by their scolex  and reside in the small intestine .  Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium.  The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day).  T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids.  The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces.  T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively.
7. Hymenolepis nanaThese eggs are oval and smaller than those of H. diminuta, with a size range of 30 to 50 µm.  On the inner membrane are two poles, from which 4-8 polar filaments spread out between the two membranes.  The oncosphere has six hooks.
8. ENTEROBIUSEggs are deposited on perianal folds .  Self-infection occurs by transferring infective eggs to the mouth with hands that have scratched the perianal area .  Person-to-person transmission can also occur through handling of contaminated clothes or bed linens.  Enterobiasis may also be acquired through surfaces in the environment that are contaminated with pinworm eggs (e.g., curtains, carpeting).  Some small number of eggs may become airborne and inhaled.  These would be swallowed and follow the same development as ingested eggs.  Following ingestion of infective eggs, the larvae hatch in the small intestine  and the adults establish themselves in the colon .  The time interval from ingestion of infective eggs to oviposition by the adult females is about one month.  The life span of the adults is about two months.  Gravid females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area .  The larvae contained inside the eggs develop (the eggs become infective) in 4 to 6 hours under optimal conditions .  Retroinfection, or the migration of newly hatched larvae from the anal skin back into the rectum, may occur but the frequency with which this happens is unknown.
9. Fertilized egg of A. lumbricoides in an unstained wet mount of stool, 200× magnification.  A larva is visible in the egg.
10. EchinostomaAdultAdult measure 2.5-6.5 x 1.1 mm.Elongated,rounded tapering ends,posterior more attenuate.Note: A horseshoe-shaped collar,bearing one or two rows of straight spines,which surrounds the dorsal and lateral sides of the oral sucker.Rounded or with indented lobes testes situated in posterior half.Transversely oval ovary in midline.are much longer than wide and measure about 2-10 mm long by 1-2 mm wide, depending on the species.  The oral sucker is surrounded by a collar of spines, the number of which varies among species.  The oral and ventral suckers are located fairly close to one another.  A single ovary is situated near the large, paired testes.  Adults reside in the small intestine of the definitive host.Many animals may serve as definitive hosts for various echinostome species, including aquatic birds, carnivores, rodents and humans.  Unembryonated eggs are passed in feces  and develop in the water .  The miracidium takes on average 10 days to mature before hatching  and penetrating the first intermediate host, a snail .  Several genera of snails may serve as the first intermediate host.  The intramolluscan stages include a sporocyst , one or two generations of rediae , and cercariae .  The cercariae may encyst as metacercariae within the same first intermediate host or leave the host and penetrate a new second intermediate host . Depending on the species, several animals may serve as the second intermediate host, including other snails, bivalves, fish, and tadpoles.  The definitive host becomes infected after eating infected second intermediate hosts .  Metacercariaeexcyst in the duodenum  and adults reside in the small intestine .
11. StrongyloidesstercoralisInfektif: larva filariform
12. D. latum
13. H. nana
14. Mature proglottid of T. solium, stained with carmine.  Note the number of primary uterine branches (<13).Life cycle of Taeniasaginata and Taeniasolium Taeniasis is the infection of humans with the adult tapeworm of Taeniasaginata or Taeniasolium.  Humans are the only definitive hosts for T. saginata and T. solium.  Eggs or gravid proglottids are passed with feces ; the eggs can survive for days to months in the environment.  Cattle (T. saginata) and pigs (T. solium) become infected by ingesting vegetation contaminated with eggs or gravid proglottids .  In the animal's intestine, the oncospheres hatch , invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci.  A cysticercus can survive for several years in the animal.  Humans become infected by ingesting raw or undercooked infected meat .  In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years.  The adult tapeworms attach to the small intestine by their scolex  and reside in the small intestine .  Length of adult worms is usually 5 m or less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T. solium.  The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool (approximately 6 per day).  T. saginata adults usually have 1,000 to 2,000 proglottids, while T. solium adults have an average of 1,000 proglottids.  The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces.  T. saginata may produce up to 100,000 and T. solium may produce 50,000 eggs per proglottid respectively.
15. T. saginata
16. F. BuskiInfek: metaserkaria
17. HeterophyesheterophyesIntestinal fluke, size 1-1.7 mm in length and 0.3-0.4 mm in widthLarge and strong ventral suckerGenital sucker (gonotyle), with spines, is adjacent to ventral suckerTwo oval testes situated posterior part of the body
18. MetagonimusAdults release fully embryonated eggs each with a fully-developed miracidium, and eggs are passed in the host’s feces .  After ingestion by a suitable snail (first intermediate host), the eggs hatch and release miracidia which penetrate the snail’s intestine .  Snails of the genus Semisulcospira are the most frequent intermediate host forMetagonimusyokogawai.  The miracidia undergo several developmental stages in the snail, i.e. sporocysts , rediae , and cercariae .  Many cercariae are produced from each redia.  The cercariae are released from the snail  and encyst as metacercariae in the tissues of a suitable fresh/brackish water fish (second intermediate host) .  The definitive host becomes infected by ingesting undercooked or salted fish containing metacercariae .  After ingestion, the metacercariaeexcyst, attach to the mucosa of the small intestine  and mature into adults (measuring 1.0 mm to 2.5 mm by 0.4 mm to 0.75 mm) .  In addition to humans, fish-eating mammals (e.g., cats and dogs) and birds can also be infected by M. yokogawai .
19. H. diminuta
20. D. caninum