TREMATODES Department of Microbiology and Parasitology

TREMATODES

Department of Microbiology and Parasitology

CLASSIFICATION OF MEDICALLY IMPORTANT GROUPS AND SPECIES OF TREMATODES

• PHYLUM: Platyhelminthes CLASS: Trematoda (flukes)

Subclass Digenea1. Order Strigeiformes

a. Superfamily Schistosomatoidea Family Schistosomatidae

1) Schistosoma haematobium2) Schistosoma mansoni3) Schistosoma japonicum


1. Order Strigeiformesb. Superfamily Echinostomatoidea

Family FasciolidaeFasciola hepaticaFasciola giganticaFasciolopsis buski

Family EchinostomatidaeEchinostoma ilocanum



Subclass Digenea2. Order OpisthorchiformesFamily OpisthorchiidaeGenus ClonorchisClonorchis sinensisGenus OpisthorchisOpisthorchis felineusOpisthorchis viverriniFamily heterophyidaeHeterophyes heterophyes



Subclass Digenea3. Order Plagiorchiformes

Family TroglotrematidaeParagonimus westermani


• Species which inhabit the portal blood stream of vertebrates.

Schistosoma japonicum Schistosoma mansoni Schistosoma haematobium


• Species which inhabit the liver of vertebrates

Fasciola hepatica Clonorchis sinensis Opisthorchis felineus


• Species which inhabit the small intestines of vertebrates Fasciolopsis buski Echinostoma ilocanumHeterophyid group

• Species which inhabit the lungs of vertebrate Paragonimus westermani

Echinostoma ilocanum

Echinostoma ilocanumEuparyphium ilocanum

Common name: Garrison’s fluke-the species was formerly Echinostoma- Huffman and Fried considered it in a related genus Eupharium

A. EPIDEMIOLOGY• the eggs of this fluke was first discovered by Garrison among

prisoners of the Bilibid Prison in Manila• Tubangi in 1933 completed its life cycle• It is endemic in the Ilocos provinces, Leyte, Samar and

Mindanao• Man acquires the infection from eating raw snail Pila luzonica called “kuhol”


B. MORPHOLOGY1. Adult• adults are reddish gray in color when alive• measuring 2.5 – 6.5 mm in length by 1 - 1.35 mm breadth• the anterior end is provided with a circumoral disk surrounded

with a crown of 49 – 51 spines • the integumen is covered with plaque-like scales• the oral sucker lies in the center of the oral disk, the ventral sucker is located in the anterior fifth of the body

proper• the tests are deeply lobed and are located posteriorly • the ovoidal ovary is located in front of the testes



B. MORPHOLOGY2. Ovum• the eggs are straw colored, operculated, ovoidal

measuring 83-116 microns by 58-69 microns• they are immature when passed in the feces• the eggs may be mistaken for Fasciola or Fasciolopsis

eggs except that they are slightly smaller and the operculum appears like a tiny dot on the egg shell



B. MORPHOLOGY3. Cercariae• has a simple tail and a body resembling in

miniature form that of the adult


C. LIFE CYCLE• The definitive host are man, dog, rats and

other snail eating mammals • The adult worms inhabit the small intestines

and lay immature eggs (unembryonated) which are passed out in the feces

• The eggs mature in fresh water in 6-15 days hatch and librates the miracidia

• The free-swimming miracidia penetrate the first intermediate host a snail

Gyraulus convexiusculus

• The miracardia metamorphose into mother rediae and produce in turn, daughter rediae and cercariae

• The free-swimming cercariae leave the body

of the snail and encyst in another fresh-water snail, Pila luzonica, the second intermediate host

• The metacercariae is the infective stage to man.

• When ingested by man or other animals it excysts and matures in the small intestines


Lumnaea spp. 2nd IH Radix spp. 1st IH

Gyraulus spp. An IH Viviparus spp. 2nd IH

Cobicula spp. 2nd IH


D. PATHOLOGY• little damage is caused to the intestinal mucosa by

attachment of these flukes• Clinical Features:

Inflammation and mild ulceration often occurs due to the penetration of the sharp-spined collar into the intestinal mucosa. In heavy infections, nausea, vomiting, diarrhea, fever and abdominal pain may occur.


E. DIAGNOSIS• specific diagnosis is based on demonstration of eggs in the patient’s

stools• Because the eggs are large, careful measurements must be taken to

avoid confusion with the eggs of Fasciola or Fasciolopsis. Species-level identification cannot be done based on egg morphology and adults are needed for a definitive diagnosis.

F. TREATMENT• Praziquantrel

G. PREVENTION AND CONTROL

• Thorough cooking of snails in endemic areas

Chlonorchis

Chlonorchis sinensis

• Common name: Chinese liver fluke- first discovered in the bile passages of a Chinese carpenter in Calcutta in 1875

A. EPIDEMIOLOGY:• occurs in large areas of China ( including Taiwan ) Japan,

Korea, and Vietnam.• Clonorchiasis has been reported in non endemic areas

(including the United States). In such cases, the infection is found in Asian immigrants, or following ingestion of imported, undercooked or pickled freshwater fish containing metacercariae.


B. MORPHOLOGY:1. Adult• of moderate size, from 1-2.5 cm. by 0.3-0.5 cm.• broadest in the midportion of the body

tapering towards both ends• adult worm live in the bile ducts and

apparently localize first in the more distal portions, just under the capsule of the liver• adult worm are known to live as long as 30

years

Clonorchis sinensis



B. MORPHOLOGY:1. Ovum• eggs resemble very closely those of

Heterophyes and Metagonimus but may have a small comma-shaped process at the abopercular end• the average length is 29 microns


Small knob at abopercular end Note operculum resting on “shoulders”



C. LIFE CYCLE:• Eggs are passed out in the feces which reaches water.• The egg is ingested by a snail and it hatches in the snails

intestine releasing a miracidium.• The miracidium bores in to the tissue of the snail producing a

cercariae.• The cercariae encyst in the second intermediate host which is

a fresh water fish producing a metacercariae.• Man gets infected by eating fresh water fish.• The metacercariae excyst in the small intestine.

Chlonorchis sinensisParafossarulus manchouricus, the most common snail host of C. sinensis in endemic areas in southeast Asia.

Bithynia sp., another common intermediate host of C. sinensis.


D. PATHOLOGY1. light infections are generally asymptomatic• heavier infections, if acquired over an extended period,

seldom cause early symptoms• the symptoms include fever, diarrhea, epigastric pain,

anorexia, enlargement and tenderness of the liver• there may be leukocytosis and eosinophilia• eggs appear in the feces after a month and acute symptoms

subside• once the acute symptoms subside persons not subject to

repeated reinfection generally do not have any recognizable symptoms from the chronic low-grade infections


D. PATHOLOGY2. Heavy worm burdens • as a result of repeated infections over a period of

years may result to localized biliary obstruction at times aggravated by intrahepatic stone formation, cholangitis and the formation of multiple liver abscesses

• cholecystisis and cholelithiasis may be the result of invasion of the gallbladder by these worms


D. PATHOLOGY• Thickening and localized dilatation of the bile ducts is

seen in heavy infections, accompanied by moderate to marked hyperplasia of the small mucinous glands

• These changes may persist for many years in patients whose infections have become very light

• Hou ( 1965 ) described adenocarcinoma (cholangiocarcinoma) arising from the hyperplastic bile duct mucosa in persons infected with C. sinensis and concluded that they have been induced by the infection


E. DIAGNOSIS:• recovery of the eggs from the feces• recovery of the eggs from duodenal aspirates or

the enteric capsule• compliment fixation and intradermal tests – not

generally available

F. TREATMENT : • Praziquantrel

Opisthorchis

Opisthorchis felineus

• as the name implies it parasitizes cats• in areas where human population eat raw fish, humans

are also infected• it also inhabits bile ducts and produces much the same

disease picture• the life cycle is also similar to Clonorchis sinensis• the adult Opisthorchis felineus differs from C. sinensis

only in some relatively minor details of structure• eggs of O. felineus are narrower than those of C.

sinensis and otherwise they are indistinguishable

Eggs of Opisthorchis spp. are 19-30 µm long by 10-20 µm wide and are often indistinguishable from the eggs of Clonorchis sinensis

The eggs are operculated and possess prominent opercular 'shoulders' and abopercular knob.

Opisthorchis

Opisthorchis

Opisthorchis felineus Opisthorchis viverrini

Clonorchis sinensisOpisthorchis felineus

Opisthorchis

Snails in the genera Bithynia and Cordiella may serve as a first intermediate host for Opisthorchis spp.

Opisthorchis• The adult flukes deposit fully developed eggs that are passed in the feces• After ingestion by a suitable snail (first intermediate host) , the eggs release

miracidia , which undergo in the snail several developmental stages (sporocysts , rediae , cercariae ).

• Cercariae are released from the snail and penetrate freshwater fish (second intermediate host), encysting as metacercariae in the muscles or under the scales .

• The mammalian definitive host (cats, dogs, and various fish-eating mammals including humans) become infected by ingesting undercooked fish containing metacercariae.

• After ingestion, the metacercariae excyst in the duodenum and ascend through the ampulla of Vater into the biliary ducts, where they attach and develop into adults, which lay eggs after 3 to 4 weeks .

• The adult flukes (O. viverrini: 5 mm to 10 mm by 1 mm to 2 mm; O. felineus: 7 mm to 12 mm by 2 mm to 3 mm) reside in the biliary and pancreatic ducts of the mammalian host, where they attach to the mucosa.

Heterophyid family

Heterophyid

THE FAMILY HETEROPHYIDAE• The more common species are the following:

Heterophyes heterophyesMetagonimus yokogawai

Heterophyid

A. EPIDEMIOLOGY• practically all species are potential parasites of man and 14

species have been found infecting man• Heterophyes and Metagonimus occur in Japan, Korea, China,

Taiwan and the Philippines• In the Philippines, dogs, cats and birds are important reservoir

host• Man acquires the infection from consumption of raw fresh water

or brackish water fishes• Fishermen, boatman, hunters, mining prospectors, rangers and

other persons whose occupations being them to close associations with marine life are probably more prone to eat fish in the raw state.

Heterophyid

B. MORPHOLOGY1. Adult• the family heterophyidae are small, elongated, oval

or pyriform, measuring less than 2 man in length • the cuticle is covered with fine scale-like spines • in other species, beside the oral and ventral suckers,

there is a genital sucker or gonotyle situated near the ventral sucker. The gonotyle is provided with spines

Heterophyes heterophyes Metagonimus yokogawai

Heterophyid

B. MORPHOLOGY2. Ovum• the eggs are minute, operculated, ovoidal, light brown in

color and measure 28-30 by 15-17 microns• the eggs when oviposited are already mature and contain

fully developed miracidia• those of heterophyes are on average very lightly larger

than those of Metagonimus but differences are too slight to be of value

• the eggs closely resemble in size and shape those of worms belonging to the genera Clonorchis and Opisthorchis

HeterophyidC. LIFE CYCLE • The definitive hosts are man, cat and other flesh eating mammals. • The adult flukes inhabit the small intestines of the definitive hosts.• Eggs containing fully developed miracidia are passed out in the feces and

upon reaching a body of water they are ingested by the appropriate snail host

• The first intermediate host may be any fresh water as brackish water snail• Inside the snail, the miracidium is liberated from the egg and passes

stages of sporocyst, one or two redial generation and then cercariae• The free living cercariae escape from the snail host and encyst in the

second intermediate hosts which may be any fresh water or brackish water fish

• The encysted metacercariae are attached to the fish scales in fins, tails and • Upon ingestion of raw infected fish the metacercariae excyst in the

duodenum and attach to the wall of the small intestines

Heterophyid

Cerithideopsilla cingulata is the main first intermediate host for H. heterophyes in southeast Asia.

Heterophyid

D. PATHOLOGY• Adult flukes provoke inflammation at the site of attachment in the

intestinal mucosa there is mild irritation, colicky pains, mucus diarrhea and superficial necrosis of the mucus coat

• In the Philippines, it has been found that heterophyid eggs or adults may

be filtered thru the intestinal wall and brought to the heart muscles via the blood circulation granulomas that form around these eggs produce cardiac insufficiency

• Eggs may also be carried to the spinal cord resulting loss of motor and sensory functions

• Eggs carried to the brain may result in seizures and neurologic deficits or even cerebral hemorrhage

Heterophyid

E. DIAGNOSIS• diagnosis is based on the recovery of eggs in the stool eggs are difficult to differentiate from those of Clonorchis and

Opistorchis• the egg contain fully developed miracidium which has the

internal organs arranged in bilateral symmetry

• Cardiac heterophyidiasis may be mistaken for cardiac beri-beri

since they resemble closely the gross appearance of the latter• there is thickening of the right ventricle however tissue

sections will reveal eggs of heterohyids or even adults

Heterophyid

F. TREATMENT• Praziquantrel 25 mg / kg p.o tid x 1 day

G. PREVENTION AND CONTROL • avoiding ingestion of raw or inadequately cooked

fresh water or brackish water fishes

Paragonimus westermani


• Common name: Oriental lung fluke Disease: Paragonimiasis

A. EPIDEMIOLOGY• because of its distribution and its spotty distribution

and its low prevalence it is not considered a public health problem at the moment

• the endemic foci are Sorsogon, Camarines, Samar, Leyte, Mindoro, Agusan and some provinces in Mindanao


B. MORPHOLOGY1. Adult• the habitat of this fluke is in the lungs where they

are encapsulated in pockets or cystic structures adjacent to the bronchi

• the adult fluke is ovoid, reddish brown in color and measures 7.5 – 12 mm in length by 4-6 mm breadth resembling a coffee bean


Adults of Paragonimus spp. are large, robust, ovoid flukes

They are hermaphroditic, with a lobed ovary located anterior to two branching testes. Like all members of the Trematoda, they possess oral and ventral suckers.



B. MORPHOLOGY2. Ovum• the eggs are golden brown in color, oral and provided with

flattened operculum which is distinctly set off from the rest of the shell by raised opercular shoulders

• the eggs measure 80-55 microns and are immature when oviposited

3. Metacercariae• round and measures not more than 0.5 mm in diameter• this is infective stage for man and other definitive hosts

they are yellow-brown, ovoid or elongate, with a thick shell, and often asymmetrical with one end slightly flattened. At the large end, the operculum is clearly visible. The opposite (abopercular) end is thickened.

The eggs are unembryonated when passed in sputum or feces.


Paragonimus westermaniC. LIFE CYCLE• adult worms are found inside the human lungs• eggs are produced and escape from the cyst into the alveoli• they are carried up into the trachea and coughed up with the sputum or

swallowed back and passed out in the feces• when eggs reach a body of water, they develop and became mature in 2-7 weeks the miracidium pushes the operculum and swims freely in the water in search for

the appropriate snails host (Brotia asperata) as its first intermediate host • Metamorphosis takes place in the snail from sporocyst to first generation redia to

2nd generation redia to cercaria• The cercaria leaves the snail and looks for its 2nd intermediate host which is a

mountain crab (Sundathelphusa philippina) where it encysts as metacercaria • Human infection takes place when man ingests infected and insufficiently cooked

crab• other animals such as cats, dogs, field rats and other rodents serve as reservoir

hosts

D. PATHOLOGY• no recognizable symptoms attend the migration of parasites• as they grow in the lungs there is an inflammatory reaction, which

may be sufficient to produce fever• when cysts rupture, a cough develops and there may be increased

production of sputum• the sputum is frequently blood tinged and may contain numerous

dark brown eggs and Charcot-Leyden crystals• the severity and progression of symptoms depends on the number

of parasites present• increasing fibrosis of the lungs occurs with longstanding infections• the clinical picture may closely resemble that of pulmonary

tuberculosis

E. DIAGNOSIS • diagnosis depends on identification of the characteristic dark golden-brown eggs

in sputum or feces, although the clinical picture may be suggestive

F. TREATMENT

• Paraziquantrel 25 mg / kg p.o. tid x 2 days or• Bithional 30-50 mg / kg p.o.

G. PREVENTION CONTROL

• for as long as man does not eat raw crabs, man will never get infection even if the infection in nature may continue amongst reservoir host

Pulmonary paragonimiasis is the most common presentation of patients infected with Paragonimus spp., although extrapulmonary (cerebral, abdominal) paragonimiasis may occur.

Detection of eggs in sputum or feces of patients with paragonimiasis is often very difficult; therefore, serodiagnosis may be very helpful in confirming infections and for monitoring the results of individual chemotherapy.

In the United States, detection of antibodies to Paragonimus westermani has helped physicians differentiate paragonimiasis from tuberculosis in Indochinese immigrants.

The complement fixation (CF) test has been the standard test for paragonimiasis; it is highly sensitive for diagnosis and for assessing cure after therapy. Because of the technical difficulties of CF, enzyme immunoassay (EIA) tests were developed as a replacement. The immunoblot (IB) assay performed with a crude antigen extract of P. westermani has been in use at CDC since 1988. Positive reactions, based on demonstration of an 8-kDa antigen-antibody band were obtained with serum samples of 96% of patients with parasitologically confirmed P. westermani infection. Specificity was >99%; of 210 serum specimens from patients with other parasitic and non-parasitic infections, only 1 serum sample from a patient with Schistosoma haematobium reacted. Antibody levels detected by EIA and IB do decline after chemotherapeutic cure but not as rapidly as those detected by the CF test.

Most published literature deals with pulmonary paragonimiasis due to P. westermani although in some geographic areas other Paragonimus species cause similar or distinct clinical manifestations in human infections. Cross-reactivity between species does occur but at varying levels for different species. Thus, use of a test for P. westermani may not allow detection of antibodies to other Paragonimus species.

TrematodesSchistosoma mansoni 140 mm x 66 mm.

Range, 114-180 mm x 45-73 mm.

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 mm x 70 mm. Range, 68-100 mm x 45-80 mm.

Oval. Small lateral spine is often seen or may appear as a small hook or "knob" located in a depression in the shell.


Found in feces. Often coated with debris and may be overlooked.

Schistosoma haematobium 143 mm x 60 mm. Range, 112-170 mm x 40-70 mm.

Elongated with rounded anterior end and terminal spine at posterior end.


Terminal spine. Found in urine, occasionally in feces. Egg often covered with debris.

Schistosoma intercalatum 175 mm x 60 mm. Range, 140-240 mm x 50-85 mm.

Elongated with tapered anterior end and terminal spine. Sometimes "spindle-shaped."


Terminal spine long, slender with bent tip. Resembles S. haematobium egg except it is longer, is thinner, and has a longer spine. Found in feces. May have debris adhering to shell.

Schistosoma mekongi 69 mm x 56 mm* Range, 51-73 mm x 39-66 mm.

Spherical. Small lateral spine, not always visible or may appear as a small "knob" in a depression in the shell.


Found in feces. Closely resembles S. japonicum egg except it is smaller. May be coated with debris.

Clonorchis sinensis 30 mm x l6 mm. Range, 27-35 mm x 11-20 mm.

Small, ovoidal, or elongated with broad rounded posterior end and a convex operculum resting on "shoulders." 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.

Opisthorchis felineus 30 mm x 12 mm. Range, 26-30 mm x 11-15 mm.

Elongated with operculum on anterior end and pointed terminal "knob" on posterior end.


Lacks prominent shoulders characteristic of Clonorchis and has more tapered end.

Heterophyes heterophyes 28 mm x 15 mm. Range, 28-30 mm x 15-17 mm.

Small, elongated or slightly ovoidal. Operculum. Slight "knob" at posterior end.


Resembles Clonorchis egg but with less distinct shoulders. Operculum is broader than in Clonorchis.

Metagonimus yokogawai 28 mm x 17 mm. Range, 26-30 mm x 15-20 mm.

Small, elongated or ovoidal. Operculum. No "shoulders" at anterior end. Small "knob" often seen on posterior end.


Resembles Clonorchis and Heterophyes eggs. Shell is slightly thinner than Heterophyes. Operculum is broader than Clonorchis.

Paragonimus westermani 85 mm x 53 mm. Range, 68-118 mm x 39-67 mm.

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 brown.

Unembryonated. Filled with yolk material in which a germinal cell is imbedded. Cells are irregular in size.

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 hepatica 145 mm x 80 mm. Range, 120-150 mm x 63-90 mm.

Ellipsoidal, thin shell. Small, indistinct operculum.

Yellow to light brown. Unembryonated. Filled with yolk cells in which an indistinct germinal cell is imbedded.

Large size. Broadly oval eggs.

Fasciolopsis buski 140 mm x 80 mm. Range, 130-159 mm x 78-98 mm.

Ellipsoidal, thin 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.

THE END

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TREMATODES Department of Microbiology and Parasitology