TREMATODES Faculty: AGUAZIM SAMUEL, M.D. Lange Chapter 55Lange
Chapter 55 Slide 2 Slide 3 Slide 4 A 34-year-old Brazilian man
presented with a 24-year history of prominent, progressively
dilating superficial veins. The veins of the lower limbs dilated
first, gradually becoming discolored and indurated (Panel A). After
5 years, varicosities appeared on the anterior chest and abdominal
wall (Panel B). Gynecomastia, splenomegaly, and bilateral
varicoceles also developed. Jaundice, spider angiomata, and
testicular atrophy were not seen. There was no evidence of liver
failure; however, a platelet count of 20,000 per cubic millimeter
indicated thrombocytopenia. Duplex Doppler ultrasonography of the
abdomen showed periportal fibrosis, splenomegaly, and high portal
flow. Esophagogastroduodenoscopy confirmed the presence of
esophageal varices. Viable eggs ofSchistosoma mansoni were found in
stool specimens, which confirmed the diagnosis of intestinal
schistosomiasis leading to portal hypertension and splenic
sequestration. He was treated with praziquantel and cleared the S.
mansoni infection. Despite evidence of profound portal
hypertension, he has done well. More than 200 million people
worldwide are infected with schistosomes. Of these, approximately
120 million have symptoms and 20 million are severely ill. During
the past decade, targeted interventions combining snail control,
improved water quality, and the treatment of infected persons have
contributed to diminishing the burden of disease. Slide 5 Slide 6
Trematodes chapter 55 General characteristics Trematodes are
commonly called flukes Are leaf shape worms which are generally
flat and fleshy Are hemophrodite except for schistosoma, which have
separate male and female Have complicated life cycle occuring in
two or more host have operculated eggs( except for schistosoma)
which contaminated water, perpetuating the life cylce and which are
also used to diagnose infections. The first intermediate hosts are
snails. Slide 7 Trematodes The most important trematodes are:
Schistosoma species (blood flukes) Clonorchis (liver fluke)
Paragonimus (lung fluke). Schistosomes have by far the greatest
impact in terms of the number of people infected, morbidity, and
mortality. Slide 8 SCHISTOSOMA Disease: Schistosomiasis.
Schistosoma mansoni, Schistosoma japonicum affect the
gastrointestinal tract. Schistosoma haematobium affects the urinary
tract. Slide 9 Epidemiology: Approximately 250 million people are
infected with schistosomes and 600 million are at risk Slide 10
SCHISTOSOMA Characteristics: Trematode (blood fluke). Adults exist
as two sexes but are attached to each other. Eggs are distinguished
by spines: - Schistosoma mansoni has large lateral spine. -
Schistosoma japonicum has small lateral spine - Schistosoma
haematobium has terminal spine Slide 11 Male and female
schistosomes Slide 12 Schistosoma mansoni has large lateral spine
Slide 13 with small lateral spine Egg of Schistosoma japonicum with
small lateral spine Slide 14 Schistosoma haematobium has terminal
spine. Slide 15 with terminal spine Eggs of Schistosoma haematobium
with terminal spine Slide 16 Slide 17 Free-swimming forked tail
cercariae Slide 18 Life cycle of SCHISTOSOMA In the venous site,
the female lays fertilizing eggs which penetrate the gut or bladder
wall. The eggs are excreted in the stool or urine and must enter
fresh water to hatch. Once hatched, the ciliated larvae (miracidia)
penetrate snails and undergo further development into sporocysts
and multiplication occurs to produce many free- swimming cercariae
Humans are infected by free-swimming forked tail cercariae that
penetrate the skin. Cercariae form larvae schistosomula that
penetrate blood vessels and are carried to the lung and the liver,
where they become adults flukes. Slide 19 Schistosoma Pathogenesis:
Eggs in tissue induce inflammation, granulomas, fibrosis, and
obstruction, especially in liver and spleen hepatosplenomegaly. S.
mansoni damages the colon (inferior mesenteric venules) S.
japonicum damages the small intestine (superior mesenteric venules)
S. haematobium damages the bladder venules which can lead to
carcinoma of the bladder Slide 20 Schistosoma Transmission:
Transmitted by penetration of skin by cercariae. Humans are
definitive hosts; snails are intermediate hosts. Endemic in
tropical areas: S mansoni in Africa and Latin America, S
haematobium in Africa and Middle East, S japonicum in Asia Slide 21
Schistosoma haematobium eggs in section of bladder Slide 22 Portal
obstruction, in liver and spleen (hepatosplenomegaly) Slide 23
Slide 24 Schistosoma Laboratory Diagnosis: Eggs visible in feces or
urine. Treatment:Praziquantel. Prevention: Proper disposal of human
waste. Swimming in endemic areas should be avoided. Slide 25
Immunity: IL-4 and IL-5 induces B cells to class- switch to
produces IgE. IL-5, which induces bone marrow precursors to
differentiate into eosinophils IL-3 (along with IL-4), which
stimulates mast-cell growth. Ag / Ab activate complement. Slide 26
Clonorchis sinensis Disease: Clonorchiasis (chinese liver fluke)
Characteristics: Trematode (liver fluke). Life cycle: Humans ingest
undercooked fish containing encysted larvae (metacercariae) In
duodenum, immature flukes enter biliary duct, become adults, and
release eggs that are passed in feces. Eggs are eaten by snails;
the eggs hatch and form larvae. These multiply through generations
and then produce many free- swimming cercariae, which encyst under
scales of fish and are eaten by humans Slide 27 Clonorchis sinensis
adult Slide 28 Clonorchis sinensis Transmission: eating raw or
undercooked freshwater fish. Humans are definitive hosts; snails
and fish are first and second intermediate hosts, respectively.
Endemic in Asia. Pathogenesis: Inflammation of biliary tract.
Laboratory Diagnosis: Brownish, small, operculated eggs visible in
feces. Treatment:Praziquantel. Prevention:Adequate cooking of fish.
Proper disposal of human waste. Slide 29 Symptoms: irritation of
the bile ducts which become dilated and deviated. The liver may
enlarge, become necrotic and tender and its function may be
impaired. Modest infections results in indigestion, weakness and
loss of weight. Heavier infections produce anemia, liver
enlargement, slight jaundice, edema, and diarrhea. Slide 30
Clonorchis sinensis operculated, brownish, Small egg Slide 31
Paragonimus Westermani Disease: Paragonimiasis. Characteristics:
Trematode (lung fluke). Slide 32 LIFE CYCLE Humans ingest
undercooked freshwater crab meat containing encysted larvae
(metacercariae). In gut, immature flukes enter peritoneal cavity,
burrow through diaphragm into lung parenchyma, and become adults
and produce eggs that enter bronchioles and are coughed up or
swallowed. Eggs in either sputum or feces that reach fresh water
hatch into miracidia that enter snails, multiply through
generations into larvae, and then form many free- swimming
cercariae that infect and encyst in crabs. Slide 33 Paragonimus
Westermani Transmission: Transmitted by eating raw or undercooked
crab meat. Humans are definitive hosts; snails and crabs are first
and second intermediate hosts, respectively. Endemic in Asia and
India. Slide 34 Paragonimus westermani egg Slide 35 Paragonimus
Westermani Pathogenesis: Inflammation and secondary bacterial
infection of lung. Laboratory Diagnosis: Eggs visible in sputum or
feces. Treatment:Praziquantel. Prevention:Adequate cooking of
crabs. Proper disposal of human waste. Slide 36 Features of
medically important trematodes Slide 37 Serum creatinine
concentration is used clinically as a convenient index of kidney
function, but it is important to remember that even a minimal
elevation in creatinine can reflect significantly decreased rate of
glomerular filtration. Hematocrit (varies with altitude): Male:
40.7-50.3% Female: 36.1-44.3% Slide 38 Increased eosinophils
(eosinophilia) is most often associated with allergic diseases and
parasites (such as worms). Possible disorders include: eczema
leukemia autoimmune diseases asthma hay fever Medications that may
cause an increase in eosinophils include: amphetamines (appetite
suppressants) tranquilizers bulk-type laxatives containing psyllium
certain antibiotics Slide 39 Slide 40 Slide 41 Slide 42 Other minor
parasite Fasciola Hepatica ( sheep liver fluke) Acquisition
Ingestion of aquatic plants, water cress Reserviour: sheep, cattle,
humans Dz: subclical- fever, nightsweats, malaise Rx: praziquantel
Slide 43 Fasciolopsis buski (giant intestinal fluke) Acquisition
Ingestion of acquatic plants, water chestnuts. Reserviour Host:
pigs, dogs, rabbits and humans Progression in humans Asymptomatic-
abd pain and diarrhea Dx: eggs in feces Rx: Praziquantel Slide 44
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