Trematodes
Phylum Platyhelminthes, 7. All are transmitted via oral/ingestion except
class Trematoda, Schistosomes.
subclass Diginea 8. Infective stage is metacercaria except Schistosomes.
9. All possess two muscular suckers except H.
also referred to as “Flukes” heterophyes.
flattened, leaf shaped, non-segmented
some species appear elongated and cylindrical Larval stages of Trematodes
1. Miracidium–a ciliated larval stage that emerged for
adult flukes are covered with a metabolically active the trematode egg.
tegument equipped with spines and have no anal 2. Sporocyst–a saclike structure that produces
opening secondary larval stages and is the first larval stage in
all adult flukes are equipped with two muscular the developmental cycle in the snail host.
suckers: 3. Redia–a larval stage with an oral sucker that is
a. Oral sucker –anterior portion, opening to the oral produced by sporocyst. Absent inblood flukes.
cavity; ingestion 4. Cercaria–a free swimming larva of trematodeswhich
b. Ventral sucker/Acetabulum – ALWAYS larger, escapes from a sporocystor redia. Infective stage of
posterior to the oral sucker; for attachment Schistosomes.
5. Metacercaria–an encysted larva found in the 2ndIH.
Classification of Trematodes Infective stage of hermaphroditic flukes.
1. Hermaphroditic/Organ dwelling flukes: inhabits
host organs Laboratory Diagnosis
o equipped with both male and female Specimen of choice: Specie dependent
reproductive organs o Feces
o may be found in the intestines, liver, pancreas o Duodenal drainage
and lungs o Rectal biopsy
2. Blood flukes: inhabits host blood vessels around o Sputum
liver, intestinal tract or urinary bladder o Urine
o separate sexes (dioecious) Eggs are the primary morphologic form seen
o includes Schistosomaspp. Serologic tests are available
Classification of Trematodes Pathogenesis and Clinical Symptoms
1. Intestinal species Symptoms vary by infection and affected areas, may
a. Fasciolopsis buski–Large intestinal fluke include:
b. Heterophyes heterophyes–Heterophyid fluke a. Eosinophilia
c. Metagonimus yokogawai–Heterophyidfluke b. Allergic and toxic reactions
2. Liver species c. Tissue damage
a. Fasciola hepatica –Sheep liver fluke d. Jaundice
b. Clonorchissinensis–Chinese liver fluke e. Diarrhea
3. Lung species
a. Paragonimuswestermanni–Oriental lung fluke
*diagnosis is in stool, sputum
4. Blood species
a. Schistosomajaponicum–Manson’s blood fluke
b. Schistosomamansoni–Blood fluke
c. Schistosomahaematobium–Bladder fluke
*diagnosis is in urine
Generalities of Trematodes
1. All have well developed reproductive organs.
2. Alimentary canal is incomplete.
3. All are flat and leaf like except Schistosomes.
4. All are hermaphroditic except Schistosomes.
5. All are operculated except Schistosomes.
6. All requires 2 intermediate hosts except
Schistosomes.
PEREZ
TREMATODES
Fasciolopsis - large, ovoid, yellowish
brown
buski/ Fasciola - operculated
spp. egg - with well-rounded
posterior end often
described as “hen egg”
shaped
- released immature
Fasciolopsis
buski adults
Fasciolopsis
buski
intermediate
host
Fasciola - large, flat, leaf like
- with cephalic cone with
hepatica wide base (shoulders) at
adult the
anterior portion
Fasciola - longer, with less
developed
gigantica adult shoulders and shorter
cephalic cone
Echinostoma - tegument is covered with
plaque like scales
ilocanum adult - anterior end is equipped
with
circumoral disk (a.k.a
collar bone; 49-51 hooks)
PEREZ
Echinostoma - straw colored, ovoid
- operculated
ilocanum egg
Echinostoma
ilocanum
intermediate
hosts
Clonorchis - thick shell, operculated
- “bell shaped”
sinensis egg - thickened opercular rim
(shoulders)
- small polar knob opposite
the operculum
Clonorchis
sinensis adult
worm
Opistorchis
felineus
Opistorchis
viverrini
PEREZ
Fasciolopsis buski
largest intestinal trematode of humans and pigs
Common Name: Giant Intestinal fluke
Final host: humans, dogs
1st IH (snail):
o Segmentinacoenosus, Hippeutiscantori
nd
2 IH (water plants):
o Trapabicornis (“water caltrop”)
o Eliocharistuberosa(“water chestnut”)
Eggs are similar to Fasciola spp. and therefore cannot be
differentiated.
Fasciola spp.
Common Name:
o Sheep liver fluke = Fasciola hepatica
o Giant/Tropical liver fluke = Fasciola gigantica
MOT: Ingestion of improperly cooked water plants
Habitat: liver and biliary passages (bile ducts)
1st IH (snail):
o Lymnaea philippinensis , Lymnaea auricularia rubiginosa
2nd IH (water plants):
o Ipomea obscura (morning glory or kangkong)
o Nasturtium officinale (water cress)
Laboratory Diagnosis b) Fascioliasis (sheep liver rot)
a) Specimen of choice: stool 1. Acute:
- eggs are indistinguishable dyspepsia,
- symptoms and travel history may be helpful fever and
b) Speciation may be done via: right upper quadrant abdominal pain
- recovery of adult Fasciolopsis worm 2. Chronic:
- Enterotest, ELISA, gelldiffusion or other parasite reach bile ducts
methodology to recover adult Fasciola
Treatment
Pathogenesis and Clinical Symptoms 1. F. buski
a) Fasciolopsis Praziquantel
abdominal discomfort 2. F. hepatica
edema dichlorophenol(bithionol)
Inflammation success has been documented with
Malabsorption syndrome triclabendazole, but it is not available in
bleeding of affected area the U.S.
intestinal obstruction
diarrhea Prevention and Control
death (rare) 1. Exercising(especially in areas known to harbor
gastric discomfort reservoir host):
a. Proper human fecal disposal
b. Sanitation practices
2. Controlling snail population
3. Avoiding consumption of raw water plants or
contaminated water
PEREZ
Echinostoma ilocanum
Common Name: Garrison’s fluke
1st IH (snail):
o Gyraulusconvexiusculus, Hippeutisumilicalis
2nd IH (snail):
o Pilaluzonica(“kuhol”)
o Vivipara angularis(“susongpampang”)
Laboratory Diagnosis: detection of eggs in stool
Pathogenesis: inflammation, ulceration, diarrhea,
intoxication due to metabolites from the parasite
Treatment: Praziquantel (25mg/kg, 3)
Prevention and Control:
o proper sanitation procedures
o avoidance of raw or undercooked 2nd IH
Clonorchis sinensis
Common Name: Oriental/Chinese liver fluke
MOT: Ingestion of improperly cooked freshwater fish
1stIH (snail): Parafossarulus/Bulimus/Aloncima
2ndIH (fish): Ctenopharyngodonidellus(Cypirinidaefish)
Laboratory Diagnosis:
- detection of eggs in stool or duodenal aspirates
- Enterotest may also be performed
- adults may be removed during surgery or autopsy
procedure (rare)
Cholangiography (radiologic):
- saccular dilations of the intrahepatic bile ducts
-rapid ductal tapering toward the periphery, “arrowhead sign”
Pathogenesis and Clinical Symptoms o calculi, acute suppurative cholangitis
1. Light infections (< 100) (common bile duct), recurrent pyogenic
o asymptomatic or few non-specific cholangitis, cholecystitis (gall bladder),
clinical signs such as diarrhea and hepatitis (liver) and pancreatitis
abdominal pain (pancreas).
2. Moderate infections (101 – 1000 adults)
o fever, diarrhea, loss of appetite, rash, Epidemiology:
edema, night blindness, swollen - endemic in far East (China, Vietnam, Taiwan)
abdomen and enlargement of liver - reservoir host includes fish eating mammals, dogs and
3. Very high worm burden (25,000 flukes) cats
o acute pain in the upper right quadrant Treatment: Praziquantel and albendazole
and subside in a few weeks Prevention and Control:
4. Chronic complications - proper sanitation procedures
o liver malfunction - avoidance of raw or undercooked fish and shrimp
PEREZ
