TREMATODES

1. FLAT FLUKES/ WORMS

2. CASE -1

3. Cases of human fascioliasis in India: Tip of the iceberg
J Ramachandran1, SSR Ajjampur1, A Chandramohan2, GM Varghese3
Ramachandran J, Ajjampur S, Chandramohan A, Varghese G M. Cases of human fascioliasis in India: Tip of the iceberg. J
Postgrad Med 2012;58:150-2

4. Case – 2
• A 40‐year‐old Indian female presented with a 2‐week history of epigastric
pain, vomiting, and passage of flesh‐like material in the stool. She
provided a history of consumption of raw singhada (water caltrop). She
used to wash the kitchen utensils and raw vegetables in pond water. Blood
examination showed hemoglobin of 10.5 g/dL and normal total eosinophil
count. Stool examination was normal. Esophagogastroduodenoscopy
showed multiple live flatworms attached to the pyloric and duodenal
mucosa (Fig. ​(Fig.1).1). Worms were variable in size and reddish‐brown in
color. Endoscopic extractions of some of the worms were performed with
the help of biopsy forceps. They were fleshy, reddish brown,
dorsoventrally flattened, and leaf‐like, measuring 4.0 cm in length, 2.5 cm
in breadth, and 2.5 mm in thickness with no prominent or obvious
cephalic cone, resembling F. buski (Video Clip S1, Supporting information).
Microscopic examination of an adult worm confirmed F. buski. The patient
was treated with praziquantel 75 mg/kg in three divided doses for 1 day.
The patient was asymptomatic and doing well on follow‐up.

6. JGH Open. 2020 Apr; 4(2): 284–286.
Published online 2019 Apr 22. doi: 10.1002/jgh3.12187

7. FEATURES CESTODES
(tapeworms)
TREMATODES
(flukes)
NEMATODES
(roundworms)
Shape (adult
worm)
Platy/ flat ribbon like
Usually long
Segmented
Platy/flat leaf like
Muscular and stout
unsegmented
Cylindrical
Variable length
unsegmented
Larval forms Cysticercus
Coracidium
Procercoid, plerocercoid
Hydatid cyst
Miracidium
Sporocyst
Redia
Cercaria
Metacercaria
Rhabditiform
Filariform
Microfilaria
Hosts Two hosts (except H.nana)
Definitive host: m.c
humans (except
echinococcus)
Two hosts and 1
paratenic host
Definitive : always
human
1st IM: snail/molluscs
2nd IM: fish/crab/aq
plants
Single host-man
(except filarioidea &
dracunculoidea)
Reproductive tract Monoecious
Each segment has both
male & female organs
Monoecious except
schistosoma
Well developed and
complete
Dioecious
Alimentary canal Absent Present but incomplete present & complete

8. FEATURES CESTODES
(tapeworms)
TREMATODES
(flukes)
NEMATODES
(roundworms)
Excretory system Present
Flame cells, capillaries
& collecting tubules
B/L Symmetrical
Flame cells &
collecting tubules
Not well developed
Nervous system
Examples
Present only in scolex
Taenia, echinococcus,
h.nana
Present
Ganglion and nerve
trunks
Schistosoma,
fasciola, clonorchis,
Rudimentary

9. TREMATODES/ FLUKES
These are leaf like or flattish, hence are also called
BLOOD FLUKES-
Schistosoma
INTESTINAL FLUKES-
SI- Fasciolopsis buski, Heterophyes,
Metagonimus, Watsonius
LI- Gastrodiscoides hominis
TISSUE FLUKES-
LIVER- Fasciolola hepatica, F. gigantica, Clonorchis
sienensis, Opistorchis
LUNG- Paragonimus westermani

10. General characters
• Adult trematodes are leaf shaped, flat unsegmented
worms.
• Organs of attachment c/d “suckers”.
– Oral suckers- around mouth & ventral sucker on ventral
surface of body
• It lives in the intestine, liver, lung or blood vessels of
humans.
• Hermophrodites (dioecious) except Schistosomes
(monoecious).
• Reproductive system- well developed and complete
• Alimentary canal- present but incomplete
• Excretory system- B/L symmetrical
– “Flame cells” present- basis of identification of species.

11. • Trematodes are oviparous and lay
operculated eggs, except in case of
schistosomes.
1. Embroyanted eggs- Schistosoma
2. Unembroyanated eggs which mature in
water- Fasciola, Fasciolopsis and
Paragonimus
3. Embroyanted eggs but hatch only in a
suitable host- Clonorchis & Metagonimus

12. Trematodes

13. Fasciola hepatica
Fasciola gigantica

14. Causal Agent
• The trematodes Fasciola hepatica (also known as the common liver
fluke or the sheep liver fluke) and Fasciola gigantica are large liver
flukes (F. hepatica: up to 30 mm by 15 mm; F. gigantica: up to 75
mm by 15 mm), which are primarily found in domestic and wild
ruminants (their main definitive hosts) but also are causal agents of
fascioliasis in humans.
• Although F. hepatica and F. gigantica are distinct species,
“intermediate forms” that are thought to represent hybrids of the
two species have been found in parts of Asia and Africa where both
species are endemic. These forms usually have intermediate
morphologic characteristics (e.g. overall size, proportions), possess
genetic elements from both species, exhibit unusual ploidy levels
(often triploid), and do not produce sperm. Further research into
the nature and origin of these forms is ongoing.

15. Immature eggs are discharged in the biliary ducts
and passed in the stool .
Eggs become embryonated in freshwater over ~2
weeks ; embryonated eggs release miracidia ,
which invade a suitable snail intermediate host.
In the snail, the parasites undergo several
developmental stages (sporocysts , rediae , and
cercariae ). The cercariae are released from the
snail and encyst as metacercariae on aquatic
vegetation or other substrates.
Humans and other mammals become infected by
ingesting metacercariae-
contaminated vegetation (e.g., watercress) .
After ingestion, the metacercariae excyst in the
duodenum and penetrate through the intestinal
wall into the peritoneal cavity.
The immature flukes then migrate through the liver
parenchyma into biliary ducts, where they mature
into adult flukes and produce eggs .
In humans, maturation from metacercariae into
adult flukes usually
takes about 3–4 months; development of F.
gigantica may take somewhat longer than F.
hepatica.

16. Hosts
• Fasciola hepatica and F. gigantica are primarily parasites of
domestic and wild ruminants (most commonly, sheep, cattle, and
goats; also, camelids, cervids, and buffalo). Infections occasionally
occur in aberrant, non-ruminant herbivore hosts, including equids,
lagomorphs, macropods, and rodents. Detection of Fasciola spp.
eggs in the feces of carnivores probably represents spurious
passage following consumption of contaminated liver.
• The snail intermediate hosts for Fasciola spp. are in the family
Lymnaeidae, particularly species in the genera Lymnaea, Galba,
Fossaria, and Pseudosuccinea. At least 20 snail species have been
identified as intermediate hosts for one or more Fasciola spp. Snail
species may differ with respect to their suitability to serve as
intermediate hosts for F. hepatica versus F. gigantica; host ranges
for both Fasciola spp. are a subject of ongoing research.

17. Geographic Distribution
• Fasciola hepatica is found on all inhabited continents, in more than 70
countries, particularly where sheep or cattle are raised. Human infections
have been reported in parts of Europe, the Middle East, Latin America
(e.g., Bolivia and Peru), the Caribbean, Asia, Africa, and rarely in Australia.
Although the conditions for F. hepatica life cycle exist in the some parts of
the United States, most of the reported U.S. cases of F. hepatica infection
in humans have occurred in immigrants who became infected in other
countries.
• Fasciola gigantica is mainly found in tropical and subtropical regions.
Human cases have been reported in parts of Asia and Africa, as well as in
Hawaii and Iran.
• “Intermediate forms” have been reported from areas, particularly in Asia,
where both F. hepatica and F. gigantica are endemic. However, other non-
sperm-producing forms with unusual ploidy and morphology occasionally
have been reported in areas where the two species are not sympatric
(e.g., the United Kingdom), which underscores the need for more research
into atypical forms.

18. Clinical Presentation
• Fasciola spp. infection in humans has two main phases, which may or may
not be associated with symptoms or other clinical manifestations. During
the early phase of the infection (usually referred to as the acute phase;
also, the migratory, invasive, hepatic, parenchymal, or larval phase), the
period when the larval fluke is migrating from the intestines and through
the liver parenchyma, larval migration can be associated with
inflammation, tissue destruction, and toxic/allergic reactions. Nonspecific
symptoms/signs (e.g., abdominal pain, nausea, vomiting, hepatomegaly,
malaise, fever, cough) and laboratory abnormalities (e.g., peripheral
eosinophilia, elevated transaminase levels) may develop. Occasionally,
larval flukes migrate to ectopic sites, such as the lungs, subcutaneous
tissue, pancreas, genitourinary tract, eyes, or brain.
• During the chronic phase of the infection (also referred to as the biliary or
adult phase), clinical manifestations, if any, may develop months to years
postexposure and include inflammation or blockage of bile ducts or the
gallbladder (e.g., cholangitis, cholecystitis), which can be intermittent.
Inflammation of the pancreas may also occur.

19. Fasciola hepatica eggs.
• Eggs of Fasciola spp. are broadly
ellipsoidal, are operculated,
measure 130–150 µm long by 60–
90 µm wide, and are passed
unembryonated in
feces. Fasciola spp. eggs can be
difficult to distinguish
from Fasciolopsis buski eggs,
although the abopercular end
of Fasciola spp. eggs often have a
roughened or irregular area. Eggs
are often reported as
“Fasciola/Fasciolopsis” eggs due
to morphologic overlap. Also, egg
size cannot reliably distinguish F.
hepatica from F. gigantica.

20. F. hepatica adults.
Adults of Fasciola hepatica are large and broadly-flattened, measuring up to 30 mm long and 15
mm wide. The anterior end is cone-shaped, unlike the rounded anterior end of Fasciolopsis buski.
Adults reside in the bile ducts of the liver in the definitive host.
F. hepatica adults observed in endoscopic retrograde cholangiopancreatography (ERCP).
Adults of Fasciola hepatica observed with endoscopic retrograde
cholangiopancreatography (ERCP) imaging.

21. Intermediate hosts of Fasciola spp.
Members of the genus Fasciola require a snail in the family Lymnaeidae to complete
their life cycle. The species of snail can vary, in terms of location, habitat and
elevation. In places where both F. hepatica and F. gigantica occur, each species of fluke
has its own species or more of intermediate hosts.

22. Diagnostic Findings
• Eggs can be detected by light microscopy during the chronic (adult)
phase of infection. Eggs can be recovered from stool or material
obtained by duodenal or biliary drainage or aspiration. F.
hepatica and F. gigantica eggs are effectively morphologically
indistinguishable and also can be difficult to distinguish from (or can
be confused with) eggs of Fasciolopsis buski and eggs of
some Echinostoma spp. Adult flukes may be detected with
endoscopic retrograde cholangiopancreatography [ERCP]). Migrating
larval flukes may be detected in histologic sections.
• False fascioliasis (pseudofascioliasis) refers to the presence of eggs in
the stool not because of an actual infection but rather because of
recent ingestion of liver contaminated with eggs, which are not
infective for humans. The potential for misdiagnosis can be avoided
by having the patient abstain from eating liver for several days before
a repeat stool examination.

23. Antibody Detection
• Serologic testing can be useful in the acute phase of infection because specific antibodies
to Fasciola may become detectable 2 to 4 weeks after acquisition of infection, whereas egg
production typically does not start until at least 3 to 4 months after exposure. Serologic testing can
also be of value for cases of chronic Fasciola infection in persons with low-level or sporadic egg
production, as well as in persons with ectopic infection. It may also help rule out pseudofascioliasis
associated with ingestion of parasite eggs in sheep or beef liver.
• The typical approach for immunodiagnosis of human F. hepatica infection includes use of an
enzyme immunoassay (EIA) with excretory-secretory (ES) or recombinant antigens and
confirmatory testing of EIA-positive specimens with an immunoblot assay.
• CDC has developed a CLIA-approved immunoblot assay for the diagnosis of Fasciola infection,
which is based on a recombinant F. hepatica antigen (FhSAP2)*. A positive reaction is defined as the
presence of a band at ~38 kDa. The sensitivity of the assay is ≥94% (16/17) and the specificity is
≥98% (113/115) for humans with chronic Fasciola infection. This assay has not yet been validated
for acute Fasciola infection.
• *Shin, S.H., Hsu, A., Chastain, H.M., Cruz, L.A., Elder, E.S., Sapp, S.G., McAuliffe, I., Espino, A.M. and
Handali, S., 2016. Development of two FhSAP2 recombinant–based assays for immunodiagnosis of
human chronic fascioliasis. The American Journal of Tropical Medicine and Hygiene, 95(4), pp.852-
855.
• Laboratory Safety
• Standard precautions apply for the processing of stool, serum, and tissue specimens. Fasciola spp.
eggs cannot infect humans because of the need for larval development in an intermediate host
(snail).

24. Treatment
• Triclobendazole

25. Prevention
• Snail population control?
• Treatment of animals for fasciolosis -
indiscriminate anthelmintic usage?
• Vaccination?

26. Fasciolopsis Buski

27. Fasciolopsis buski
• Common name- SI fluke- Largest
trematode
• Asia Giant Intestinal Fluke
• Geo. Distribution-
– India -Assam, W. Bengal,
SE Asia - China, Korea, Taiwan,
Vietnam, Thailand and Bangladesh.
• Prevalence is related to
growing and feeding of
pigs on water plants
• Habitat SI fluke- man, pig

28. Life cycle
Transmission
Human infection is acquired by ingesting
metacercariae encysted on row aquatic vegetable
when they are peeled with teeth or by eating.
• Two different hosts
Definitive host
Man, pig, dog or rabbit.
Intermediate host
Snail

29. The trematode Fasciolopsis buski, the largest
intestinal fluke of humans.
Life Cycle
Immature eggs are discharged into the
intestine and stool. Eggs become embryonated
in water, eggs release miracidia, which invade a
suitable snail intermediate host .
In the snail the parasites undergo several
developmental stages (sporocysts , rediae, and
cercariae ). The cercariae are released from
the snail and encyst as metacercariae on
aquatic plants .
The mammalian hosts become infected by
ingesting metacercariae on the aquatic plants.
After ingestion, the metacercariae excyst in the
duodenum and attach to the intestinal wall.
There they develop into adult flukes (20 to 75
mm by 8 to 20 mm) in approximately 3 months,
attached to the intestinal wall of the
mammalian hosts (humans and pigs) .
The adults have a life span of about one year.
Geographic Distribution
Asia and the Indian subcontinent, especially in areas where humans
raise pigs and consume freshwater plants.
.

30. • Adult:
• Size is about 20-75× 8-20 ×1-
3mm, found in man & pig.
• Fleshy, elongated/ elliptic with
a broad anterior end.
• The ventral sucker is near by
the much smaller oral sucker.
• Morphology resembles to
F.hepatica.
25,000 eggs per day, each oval
and measuring approximately
130 x 80-85 m.

31. Egg- 15-x 90 micron, oval,
operculated, bile stained,
non-infective, doesn’t float in
saturated salt solution
Miracidium- free swimming
form, found in
fresh water
Sporocyst- snail
Redia- snail
Cercaria- snail- exit form
Metacercaria- aquatic plant
Snail in the genus Hippeutis,
an intermediate host for F.
buski. Image courtesy of
Conchology, Inc, Mactan
Island, Philippines.
Snail in the genus
Segmentina, an intermediate
host for F. buski. Image
courtesy of Conchology, Inc,
Mactan Island, Philippines.

32. Pathogenicity & C/F- Small Intestine
• Ulcer & local inflammation at site of attachment
• Light infection – asymptomatic & weakness
anemia, eosinophilia
• Heavy infection - Diarrhoea, fever, abdominal
pain. Malabsorption, protein losing enteropathy,
inc. toxin absorption leading to toxemia
• SUMMARY: Most infections are light and
asymptomatic. In heavier infections, symptoms
include diarrhea, abdominal pain, fever, ascites,
anasarca and intestinal obstruction

33. • Lab diagnosis
Stool Sample- Egg- operculated, bile stained, oval
adult worm,
serology no value.
• Treatment- Praziquantel
• Prevention- Proper cooking of Aq. Plant,
mollusucidals- Cu S O4 1: 50,000 strength
• In water

34. Fasciolopsis
buski
140 µm x 80
µm. Range,
130-159 µm x
78-98 µm.
Ellipsoidal,
thin shell.
Small,
indistinct
operculum.
Yellow
brown.
Unembryonat
ed. 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.
Eggs of Fasciolopsis buski are
broadly ellipsoidal,
operculated and measure 130-
150 µm long by 60-90 µm
wide.
The eggs are unembryonated
when passed in feces.
The eggs of F. buski can be
difficult to distinguish
from Fasciola hepatica,
although the abopercular end
of the latter often has a
roughened or irregular area

35. Treatment
• Praziquantel , adults, 75 mg/kg/day orally in
three divided doses for 1 day; the dosage for
children is the same.
• (Note: praziquantel should be taken with
liquids during a meal.)
• *Not FDA-approved for this indication

36. Paragonimus westermanii
• COMMON NAME- Oriental lung fluke
• NOMENCLATURE- Platyhelminthes- Trematodes
• GEO. DISTRIBUTION-SE Asia, South & Central
America
India- North Eastern part (max. prevalence),
Kerala, TN, Maharashtra

37. The eggs are excreted unembryonated in the sputum,
or alternately they are swallowed and passed with
stool . In the external environment, the eggs become
embryonated , and miracidia hatch and seek the first
intermediate host, a snail, and penetrate its soft
tissues .
Miracidia go through several developmental stages
inside the snail : sporocysts , rediae , with the latter
giving rise to many cercariae , which emerge from the
snail.
The cercariae invade the second intermediate host, a
crustacean such as a crab or crayfish, where they
encyst and become metacercariae. This is the
infective stage for the mammalian host .
Human infection with P. westermani occurs by eating
inadequately cooked or pickled crab or crayfish that
harbor metacercariae of the parasite . The
metacercariae excyst in the duodenum , penetrate
through the intestinal wall into the peritoneal cavity,
then through the abdominal wall and diaphragm into
the lungs, where they become encapsulated and
develop into adults . (7.5 to 12 mm by 4 to 6 mm). The
worms can also reach other organs and tissues, such
as the brain and striated muscles, respectively.
However, when this takes place completion of the life
cycles is not achieved, because the eggs laid cannot
exit these sites. Time from infection to oviposition is
65 to 90 days. Infections may persist for 20 years in
humans. Animals such as pigs, dogs, and a variety of
feline species can also harbor P. westermani.
Geographic Distribution
Paragonimus spp. are distributed throughout
the Americas, Africa and southeast
Asia. Paragonimus westermani is distributed
in southeast Asia and Japan. Paragonimus
kellicotti is endemic to North America.

38. Paragonimus westermani eggs range from 80-120 µm long by 45-70 µm wide.
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.

39. Eggs of Paragonimus spp. in tissue.
Paragonimus spp. eggs range
from 50-125 µm by 35-70
µm.
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.

40. EGGS in BAL & TISSUE

42. Adult of P. westermani.
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

43. OTHER IMP. PARAGONIMUS SPP.
• P. hetrotremus- Nagaland, Arunachal, Tripura
• P. miyazakii
• P. africanus
• P. pulmonalis

44. PATHOGENESIS
• Adult fluke- acute inflammatory reaction causing
eosinophilic granulomas & small multiple fibrous
cysts. Adult worm present inside fibrous cyst. Cysts
ususally less than 20 & m.c in right lung.
• Pathogenicity due to egg- cystic encapsulated eggs
in lung and less commonly in brain are key
pathological features.
• Cysts present in deeper layer of lungs and rupture
and open in bronchioles, if expectorated passed in
sputum and if swallowed passed in feces.

45. Clinical features
• The acute phase (invasion and migration) may be
marked by diarrhea, abdominal pain, fever, cough,
urticaria, hepatosplenomegaly, pulmonary
abnormalities, and eosinophilia.
• During the chronic phase, pulmonary manifestations
include cough, expectoration of discolored sputum,
hemoptysis, and chest radiographic abnormalities.
• Extrapulmonary locations of the adult worms result in
more severe manifestations, especially when the brain
is involved.

46. • Extra-pulmonary paragonimiasis-
– Abdominal
– Cerebral
– Subcutaneous
• Miscellaneous- kidney, testes, ovary affected

47. Diagnosis
• The clinical picture of chronic paragonimiasis resembles chronic bronchitis or
tuberculosis. Persons may cough up coffee-colored or blood-tinged sputum, often
accompanied by chest pain and/or shortness of breath. The sputum may be
peppered consisting of clumps of eggs produced by the adult fluke living in the lung.
• Peripheral eosinophilia is common and can be intense, especially during the early
larval migration stages. Many patients have a spectrum of abnormalities on chest
radiographs: lobar infiltrates, coin lesions, cavities, calcified nodules, hilar
enlargement, pleural thickening and effusions. Ring-shaped opacities of contiguous
cavities giving the characteristic appearance of a bunch of grapes are highly
suggestive of pulmonary paragonimiasis.
• Central nervous system disease may provide similar “grapebunch” findings,
characteristically seen in the temporal and occipital lobes on computed tomography
of the brain. CNS involvement occurs in up to 25% of hospitalized patients and may
be associated with Paragonimus-induced meningitis. CNS symptoms may include
headaches, seizures, and visual disturbances. Paragonimus flukes may also invade
the liver, spleen, intestinal wall, peritoneum, and abdominal lymph nodes.

48. Diagnosis
• Sputum examined microscopically may reveal Paragonimus eggs released by the
flukes in the lungs. Keep in mind that the acid-fast stain that is used for TB
testing of sputum destroys eggs. The eggs may also be found by multiple stool
exams on different days as a result of coughed-up eggs that are swallowed. The
microscopic eggs are yellowish brown, 80-120 µm long by 45-70 µm wide, thick-
shelled, and with an obvious operculum. Serologic tests can be especially useful
for early infections (prior to maturation of flukes) or for ectopic infections where
eggs are not passed in stool.
• Ectopic lesions from aberrant migration of flukes can involve any organ,
including abdominal viscera, the heart, and the mediastinum. The infection can
also affect the liver, spleen, abdomen, and skin. The most clinically recognizable
ectopic lesions arise from cerebral paragonimiasis, which, in highly endemic
countries, more commonly affects children. These children present with
eosinophilic meningoencephalitis, seizures, or signs of space-occupying lesions.
Many patients with central nervous system disease also have pulmonary
infections. P. skrjabini often produces skin nodules, subcutaneous abscesses, or
a type of creeping eruption known as “trematode larva migrans.”

49. Laboratory Diagnosis
• Morphologic Diagnosis
• Diagnosis is based on microscopic demonstration
of eggs in stool or sputum, but these are not
present until 2 to 3 months after infection. (Eggs
are also occasionally encountered in effusion
fluid or biopsy material.)
– Concentration techniques may be necessary in
patients with light infections. Biopsy may allow
diagnostic confirmation and species identification
when an adult or developing fluke is recovered.

50. LAB DIAGNOSIS
• PARASITIC DIAGNOSIS:
– Sputum microscopy
– Stool microscopy
• Demonstration of operculated eggs in both
the specimens. Presence of charcot leyden
crystals
• Sensitivity- 25-30%. Repeated examination
thus necessary

51. • SERO-DIAGNOSIS: high st &sp.
• Useful in:-
– Pre-patent period
– Extra-pulmonary paragonimiasis
• RADIOLOGICAL IMAGING:
– CXR: characterstic ring shadows
– CT, MRI brain: cluster of ‘soap
bubble’ appearance

52. Antibody Detection
• 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.

53. Antibody Detection
• 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.

54. TREATMENT
• Praziquantel is the drug of choice: adult or pediatric
dosage, 25 mg/kg given orally three times per day for 2
consecutive days. For cerebral disease, a short course
of corticosteroids may be given with the praziquantel
to help reduce the inflammatory response around
dying flukes.
• Alternative: Triclabendazole, adult or pediatric dosage,
10 mg/kg orally once or twice.
PREVENTION & CONTROL
• Avoid eating partially cooked cray/crabfish.
• Health education & sanitary measures
• Reservoir reduction

55. Species Size Shape Color
Stage of
Development
When Passed
Specific Features and
Variations
Schistosoma
mansoni
140 µm x 66 µm.
Range, 114-180
µm x 45-73 µm.
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 µm x 70 µm.
Range, 68-100
µm x 45-80 µm.
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
haematobium
143 µm x 60 µm.
Range, 112-170
µm x 40-70 µm.
Elongated with rounded
anterior end and
terminal spine at
posterior end.
Yellow or
yellow
brown.
Embryonated.
Contains mature
miracidium.
Terminal spine. Found in
urine, occasionally in feces.
Egg often covered with
debris.
Schistosoma
intercalatum
175 µm x 60 µm.
Range, 140-240
µm x 50-85 µm.
Elongated with tapered
anterior end and
terminal spine.
Sometimes “spindle-
shaped.”
Yellow or
yellow
brown.
Embryonated.
Contains mature
miracidium.
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 µm x 56 µm*
Range, 51-73 µm
x 39-66 µm.
Spherical. Small lateral
spine, not always visible
or may appear as a small
“knob” in a depression in
the shell.
Yellow or
yellow
brown.
Embryonated.
Contains mature
miracidium.
Found in feces. Closely
resembles S. japonicum egg
except it is smaller. May be
coated with debris.

56. Species Size Shape Color
Stage of
Development
When Passed
Specific Features and
Variations
Clonorchis
sinensis
30 µm x l6 µm.
Range, 27-35 µm x
11-20 µm.
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 s
pp.
30 µm x 12 µm.
Range, 26-30 µm x
11-15 µm.
Elongated with operculum
on anterior end and pointed
terminal “knob” on
posterior end.
Yellow
brown.
Embryonated.
Contains mature
miracidium.
Lacks prominent shoulders
characteristic
of Clonorchis and has more
tapered end.
Paragonimus
westermani
85 µm x 53 µm.
Range, 68-118 µm x
39-67 µm.
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.

57. THANK YOU