Trematodes: Flukes Classification and Characteristics

• Trematodes are unregimented helminthes, flat and broad, resembling leaves or flatfish.
• "Fluke" originates from the Anglo-Saxon word 'floc', meaning 'flatfish'.
• Trematodes are named for their prominent suckers with a hole in the middle
• In Greek, 'trema' means hole, and 'eidos' means appearance.

Classification Based on Habitat

• Blood flukes include Schistosoma spp.
• Liver flukes (found in the biliary tract) include Clonorchis sinensis, Fasciola hepatica, and Opisthorchis spp.
• Intestinal flukes include Fasciolopsis buski, Heterophyes heterophyes, Metagonimus yokogawai, Watsonius watsoni, and Gastrodiscoides hominis (large intestine).
• Lung flukes include Paragonimus westermani.

General Characteristics of Flukes

• Fluke sizes vary from just visible, like Heterophyes, to large and fleshy, like Fasciola and Fasciolopsis.
• Flukes have 2 muscular cup-shaped suckers (distomata): an oral sucker around the mouth and a ventral sucker (acetabulum) in the middle.
• Fluke bodies are covered by an integument that often bears spines, papillae, or tubercles.
• They lack a body cavity, circulatory, and respiratory organs.
• The alimentary system includes the mouth surrounded by the oral sucker, a muscular pharynx, and the esophagus which bifurcates to form 2 blind caeca, that reunite in some species and anus is absent.
• The excretory system has flame cells and collecting tubules, leading to a median bladder.
• Trematodes have a simple nervous system of paired ganglion cells.
• Most flukes are hermaphroditic (monoecious) but schistosomes are dioecious (sexes separate).
• Hermaphroditic flukes have both male and female structures allowing self-fertilization, though cross-fertilization also occurs.
• In schistosomes, the female fits in the gynecophoric canal of the male for close apposition.
• Trematodes are oviparous, laying operculated eggs, except for schistosomes.

Life Cycle

• Medically important trematodes are in the Digenea subclass.
• Digenea are digenetic, requiring 2 hosts to complete their life cycle.

Fasciola Hepatica

• F. hepatica was the first trematode discovered in 1379 by Jehan de Brie.
• Linneus named it in 1758.
• The largest and most common liver fluke in humans, with sheep as the primary host and cattle to a lesser extent.
• F. hepatica is worldwide, mainly in sheep-rearing areas.
• It causes the economically important disease "liver rot" in sheep.
• The parasite resides in the liver and biliary passages of the definitive host.
• It is a large, leaf-shaped fluke, 30 mm long, 15 mm broad, and grey/brown.
• The fluke has a conical anterior projection with an oral sucker and is rounded posteriorly.
• An adult worm lives in the biliary tract of the definitive host for many years: about 5 years in sheep and 10 years in humans.
• F. hepatica, like all trematodes, is hermaphroditic.
• F. hepatica eggs are large, ovoid, operculated, bile-stained, and around 140 µm by 80 µm.
• Eggs contain immature larvae, called miracidium.
• These eggs do not float in saturated salt solution.
• F. hepatica and Fasciolopsis buski cannot be differentiated from their eggs.
• The eggs are unembryonated when freshly passed.
• F. hepatica completes its life cycle with 1 definitive and 2 intermediate hosts.
• Definitive hosts include sheep, goat, cattle, and humans.
• Intermediate hosts are snails of the genera Lymnaea and Succinea encystment occurs on aquatic plants, which act as the second intermediate host.
• The infection mode is by ingesting metacercariae encysted on aquatic vegetation.
• Adult worms live in the biliary passage of sheep or humans.
• Eggs are laid and shed in feces.
• Embryos mature in water in about 10 days, and the miracidium escapes.
• It penetrates the tissue first intermediate host, snails of the genus Lymnaea.
• The miracidium progresses through sporocyst and redia stages in the snail to become cercariae in 1-2 months.
• Cercariae escape into water and encyst on aquatic vegetation to become metacercariae
• Metacercariae can survive for long periods.
• Sheep, cattle, or humans eating contaminated watercress or water vegetation become infected.
• Metacercariae excyst in the duodenum of the definitive host and pierce the gut wall to enter the peritoneal cavity.
• They penetrate the Glisson's capsule, traverse of the liver parenchyma, and reach the biliary passages, where they mature into adult worms in 3-4 months.

Pathogenicity

• Fascioliasis occurs when the parasite traverses the liver tissue, causing parenchymal injury.
• Humans have a more severe inflammatory response, as humans are not primary hosts.
• Some larvae can penetrate the liver and diaphragm, ending up in the lung.
• The acute phase causes fever, right upper quadrant pain, eosinophilia, and tender hepatomegaly.
• These symptoms subside as parasites reach their destinations.
• Ingestion of raw liver of infected sheep causes halzoun (suffocation); adult liver worms attach to the pharyngeal mucosa.
• False fascioliasis is the ingestion of infected raw liver, and the eggs are present in feces.
• Halzoun is common in Lebanon, the Middle East, and North Africa.

Diagnosis of Fasciola Hepatica

• The best method is demonstrating eggs in feces or aspirated bile from the duodenum.
• F. hepatica and F. buski eggs are indistinguishable.
• Eosinophilia is revealed in the blood.
• Serological tests like immunofluorescence, ELISA, immunoelectrophoresis, and complement fixation help detect specific antibodies in lightly-infected individuals.
• ELISA becomes positive within 2 weeks of infection and negative after treatment, but Fasciola copro-antigen can be detected in stool in chronic fascioliasis.
• Ultrasound, CT scans, and Endoscopic Retrograde Cholangiopancreatography(ERCP) may be helpful.
• Percutaneous cholangiography may be helpful in diagnosis.
• The treatment of choice is oral triclabendazole (10 mg/kg once).
• Bithionol is an alternative drug (30–50 mg for 10–15 days).
• Prednisolone at a dose of 10–20 mg/kg controls toxemia.

Blood Flukes: Schistosomes

• Schistosomes are dioecious trematodes that cause Schistosomiasis (bilharziasis).
• The disease is a water-borne health problem affecting millions in Africa, Asia, and Latin America.
• Over 100 million people are infected with S. haematobium, S. mansoni, and S. japonicum.
• Two other species of Schistosoma parasitic on humans are S. mekongi and S. intercalatum.
• The male worm is broader than the female; it is rolled ventrally into a cylindrical shape, creating a gynecophoric canal for the female.
• Hence, schistosome means split body (Greek schisto: split, soma: body).
• Schistosomes were formerly named Bilharzia after Theodor Bilharz, who first observed them in 1851 in the mesenteric veins of a patient in Cairo.
• Schistosomes differ from hermaphroditic trematodes.
• They are unisexual (dioecious).
• They lack a muscular pharynx.
• Their intestinal caeca reunite after bifurcation and form a single canal.
• Schistosomes produce non-operculated eggs.
• They lack a redia stage in larval development.
• Schistosome cercariae have forked tails and infect by penetrating unbroken skin.

Schistosoma Haematobium

• The adult worms live in the vesicle and pelvic plexuses of veins.
• Adult males are 10-15 mm long by 1 mm thick with a finely tuberculated cuticle
• They have two muscular suckers, the oral sucker being smaller, and they have a gynecophoric canal.
• Adult females are long and slender, 20 mm by 0.25 mm, with the cuticle being confined to the ends.
• The gravid female worm contains 20–30 eggs in its uterus and may pass up to 300 eggs daily.
• Schistosoma Haematobium eggs are ovoid, about 150 µm by 50mm, non-operculated, and transparent shells that each carry a terminal spine (characteristic of the species).
• The S. haematobium life cycle has 2 hosts.
• Humans are the only natural definitive hosts.
• Freshwater snails are the intermediate host.
• The infective form is cercaria larva.
• The eggs in urine are embryonated, hatch under the right conditions, and release free-living ciliated miracidia.
• Miracidia swim in water, penetrate intermediate hosts (snails of the genus Bulinus), and reach its liver.
• In Africa, it is Snail Bulinus.
• Inside the snail, miracida loses their cilia, and after 4-8 weeks, successively pass through the stage of first and second-generation sporocysts.
• Large numbers of cercariae are produced by asexual reproduction within the second generation of sporocysts
• The cercaria has an elongated ovoid body and forked tail (furcocercous cercaria).
• cercariae swim in water for 1-3 days, and they penetrate the unbroken skin.
• Skin penetrations is caused by lytic substances secreted by penetration glands.
• On entering the skin, the cercariae shed their tails and become schistosomulae, which enter peripheral venules.
• They then start through the vena cava into the right side of the heart, the pulmonary circulation, the left side of the heart, and the systemic circulation, reaching the liver.
• In the intrahepatic portal veins, the schistosomulae grow and become adolescents (about 20 days after).
• As they sexually differentiate, they start migrating against the bloodstream into the inferior mesenteric veins.
• They reach the vesicle and pelvic venous plexuses where they mature, mate, and lay eggs.
• Eggs start appearing in urine after 10-12 weeks.
• Clinical Schistosome illnesses depend on the evolution stages of infection.
• These stages include skin penetration and the incubation period, egg deposition and extrusion, and tissue proliferation and repair.
• Clinical features during this incubation period can be local cercarial dermatitis or general toxic symptoms.
• Cercarial dermatitis causes transient itching and lesions (swimmer's itch).
• Is seen more often in visitors due to repeated contacts.
• This is accompanied by leucocytosis and eosinphilia.
• A palpable version of this is Katayama Fever.

Laboratory Diagnosis

• This can be done through either urine microscopy or a bladder mucosal biopsy.
• Urine Microscopy can be done by demonstrating characteristic terminal spines by microscopic examination
• Histopathology is done with bladder musocal
• Another method of this form of detection is specific schistosome antigens
• In combination with an antibody sample.

Laboratory Diagnosis- Additional Testing

• Intradermal Skin Test (Fairley's test)
• Imaging can also be used.

Imaging

• This can be done viewing x-rays of the abdomen will show some bladder aereatal calcification.
• Untrasonography (USG) is useful here as well.

Schistosoma Haematobium Treatments

• Praziquantel is used and is to be administered (40mg/kg) for 1 day.
• The next drug choice is Metriphonate, and it is measured (7.5mg/kg) weekly for 3 weeks.

Schistosoma Mansoni

• Widely distributed in Africa, South America, and Caribbean islands.
• Adults live in the inferior mesenteric vein.
• Morphology is similar to S. haematobium, except-
• The adult worms are smaller, and integuments are studded with prominent tubercles.
• The gravid female's uterus contains 1-3 eggs only.
• The prepatent period (cercarial penetration to the beginning of eggs) is 4 to 5 weeks.
• The eggs have a characteristic lateral spine near the rounded posterior end
• Eggs are non-operculated is yellowish brown.
• The intermediate host is a Biomphalaria.
• In humans, schistosomulae mature in the liver, and the adult worms move against the bloodstream into the venules of the inferior mesenteric.
• The eggs penetrate the gut wall, reach the colonic lumen, and are shed in feces.

Other Pathogen factors of Schistosomiasis

• After penetration a pruritic rash results in swimmer's itch.
• Can develop locally
• Self limiting
• Acute versions may also cause Katayama fever, athralgia, and cough.
• During the egg deposition stage the infection spreads into the smal intestine, and is know as intestinal bilhariziasis.
• Patients develop crollickin abdiminal pain, and bloody diahreah.
• The eggs reach the Guts and cause inflammatory reactions, eventual hepatosplen, and portal Hypertension.,.

Schistosomiasis: Testing

• Lateral Spines may microscopically be demonstrated in the Stool samples.
• rectal muscosa, is the key biopsy check.
• Ultrasonography (USG) is useful to detect hepatolmagnlia.,

Schistosoma Japonicum

• Is also known as “Oriental Blood fluke”
• This is commonly located in Japan, China, Taiwan and the Philippians.
• It spreads from the illeocecal region
• The Morphology are rather similar from their counterparts
• Can be thinner in males.
• 100 eggs
• This can get passed, with 3500 eggs.
• eggs are smaller, and has shows aleratal small smpl

Schistosoma japonicum. life Cycle.

• Has a life Cycle that follows that of haematobium, with multiple
• Humans are the difinete host,
• This involves snails of the genus “Oncomelanai”
• The fork tailed Careria, are the infective human form

Pathogenicity

• This includes Oriental Schitosmais
• The acute type involves abdominal pai, and diaherrea.
• Chronic: Liver Maximally Effected. eggs in feces is an additional cause.

Nemathelminthes (Classe:Nematoda)

General Characteristics:

• They are elongated, symmetrical with tapering ends and millimeters-to-meters in length.
• They also utilize a “Pseudocoele Visercara.”
• Utilize an anterior Mouth with Esophagus.
• The have simple excretory and nervous systems,
• Utilize separate Sexes, with the aid of single testis differentiated into seminal vessels,
• females use ovaries, utherus,
• Reproduction is done through Oviparous larve.
• Can be found as parasitic worms found in Soil /Water.

Ascaris lumbricoides

• Causes asdcariasis and intestinal rounds
• Adult worms live in infected intestine
• Mostly via contact through comtatinted soil/Eggs.

Ascaris lumbricoides: Morphology

• Cylinder, Tapering ends.
• They are coloured when first passed, but quickly become white.
• They are known to have 3 distinct lips that has denticulate lips.

Male

• Can measure 15-30 cm, and curves ventrally. The vulva, has ⅓ and enormous eggs.

Eggs

• Have a longer lifespan.
• the ferilized eggs are goldenbrown
• and has thick a external layer.

Ascaris lumbricoides: eggs -unfertlized

• They are non, elgongated and cannot be effective,
• they become rhadbdiform.

Ascaris lumbricoides: life cycle

• A frequent mode is water.
• and larvae form.
• they can migrate to portal liver vessels
• after the 4th day, they will grow multpiple times
• will mature after 6-12 weeks
• The adult ones live from 12-20 montsh.

Ascaris lumbricoides; Pathigenicy

• Causes Allerici and ascarisis.

2. Loaffers Pneumonia::

• occurs if lung tissue is destroyed.

B- 2 adukt Wrom

• acids can cause nausea.
• the test involves stool collection
• and gastric waeshings.

Enterobius Vermicularis

• Pinworm, Seatworm, Threadworm; considered the worklds most common Parasite.
• • The adults live in teh cecum or appedix
• Adults are short form, and bits of white.
• The mouth is surrofned 3 cutical wings.

Morphology

• feamles range from13mm
• Mlaes can range from 5mm,

Eggs

• The eggs are colrloless and biles stained.
• They are characteristic, olongated, and co vex.

Enterobis,s Vermucialris Lifecycle

• This is monoxenoius passing through the life of humans hosts
• it follows a natural infection
• but the eggs are embedded.
• contact from contaminated fingers.

NOTE::

• Autoingfection occurs more from fingers.
• Re infection occurs in teh perenial,

Pathigency/Features

• more found i children
• worm is prrutis
• leading skin excoriation.
• The worm crawls.

Diagnostic

• Diagomsis is dependsn on a test for the perinal puritis.
• Theyare are deosited a night,.

Lab method::

• Nith Swabh.
• Scotch Method

Scotch method:

• Adhesive is used on the wooden depressor
• used the surface and then a micrpspoe

Demonstration

• occurs though noticeble worms that are at the worm,,.

Treatment:

Pyrental , albendzaole a piperazine

• has to be gyiven daliy weekly

General Nematodes/ Firlaloidea Chatacteristics/

Firlaloidea Traits:

• they are traminmitted by the biote of insects.
• females ae viviprous, known as mocroferirara.
• they occcur as adults, and larvae
• some spciex retain eegm membranes.

Lyphmatic fillarisis

Wuchereria, bancrofiti

Adult are withish, transcules, and are threadlike

• femals are langer. Malvesa

Filliria

• can be in testes.
• adult womrs for 10 years.

Translucent. trait

• they utilize thir dstage larva.

Fillirisis.

Development.

• Vector. 2- 6 hours/ penetrates .
• 4-14 muscles dewelpoiemtn mou;toimne, secondstage, third stage.

Pathigencitiy

• The typicl maniifestation of fliraaisis are cuased by adyt l worms, the wormsd causes granulosa.

Diagomsis is based on 4 features

• microfirlra derm, seorlogica.

Female ,nematodes

Un segmented= ascaristis. Segenmted - andcylomsom