TREMATODES; FASCIOLA

Question 1

Opisthorchis

Answer 1

=O. sinensis
=O. felineus
=O. viverini

Question 2

Paragonimus

Answer 2

=P. westermani
=P. kellicotti

Question 3

Fasciolopsis

Answer 3

=Fasciolopsis buski

Question 4

Fasciola

Answer 4

=Fasciola hepatica
=Fasciola gigantica

Question 5

Other

Answer 5

Echinostoma

Question 6

Reproduction in trematodes

Answer 6

=With the exception of schistosomes (blood flukes) all flukes are hermaphroditic
=Each fluke possesses both sex organs
=Self-fertilization usually takes place, but cross-fertilization can also occur

Question 7

Two Fasciola species (types) infect people, which ones are they?

Answer 7

=Fasciola hepatica, which is also known as “the common liver fluke” and
=Fasciola gigantica also known as “the sheep liver fluke.”
Can also infect humans

Question 8

Contrast the size of the two fasciola species

Answer 8

=F. hepatica measures up to 30 mm by 15 mm
=F. gigantica measures up to 75 mm by 15 mm

Question 9

Epidermiology of Fasciola

Answer 9

=Fasciola hepatic: all continents except Antarctica
=Fasciola gigantica: In some tropical areas

=Infective Fasciola larvae (metacercariae) are found in contaminated water—typically, stuck to (encysted on) water plants or, potentially, floating in the water—such as in marshy areas, ponds, or flooded pastures

Question 10

Transmission of Fasciola

Answer 10

=The main way people (and animals) become infected is by eating raw watercress or other contaminated water plants (for example, if the plants are eaten as a snack or in salads or sandwiches)
=People also can get infected by ingesting contaminated water, such as by drinking it or by eating vegetables that were washed or irrigated with contaminated water.
=Under unusual circumstances, infection might result from eating raw or undercooked sheep or goat liver that contains immature forms of the parasite.

Question 11

Lifecycle of Fasciola Species

Answer 11

1. Immature eggs are discharged in the biliary ducts and passed in the stool
2. Eggs become embryonated in freshwater over ~2 weeks.
3. Embryonated eggs release miracidia, which invade a suitable snail intermediate host.
4. In the snail, the parasites undergo several developmental stages (sporocysts-rediae-cercariae).
5. The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other substrates.
6. Humans and other mammals become infected by ingesting metacercariae-contaminated vegetation (e.g., watercress).
7. After ingestion, the metacercariae excyst in the duodenum and penetrate through the intestinal wall into the peritoneal cavity.
8. The immature flukes then migrate through the liver parenchyma into biliary ducts, where they mature into adult flukes and produce eggs.
9. 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.

Adult females can produce up to 25000 eggs per day

Question 12

F. Hepatica hosts

Answer 12

=Defintive host
*Sheep
*Cattle
*Humans (Accidental)
*Other Mammals

=Intermediate host
*Fresh Water Snail
**The snail intermediate hosts for Fasciola spp. are in the family Lymnaeidae, particularly species in the genera Lymnaea, Galba, Fossaria, and Pseudosuccinea
**Africa is Galba or Lymnaea truncatulla

=Geographic Range:
Cosmopolitan; anywhere sheep and cattle are raised

Question 13

F. hepatica Pathogenesis

Answer 13

=The majority of damage caused in the liver arises from suckers action and spiny tegument abrasions as parasite migrates through the liver parenchyma

=Mechanical damage is accompanied by cellular inflammatory reaction generated by the host, which leads to immunopathogical condition

=Haemorrhage, necrosis, fibrosis and cirrhosis are common findings during the disease

Question 14

The course of F. hepatica infection

Answer 14

①The acute phase
⓶The chronic phase
③The obstructive phase

Question 15

1. Acute Phase of F. hepatica infection

Answer 15

=Rarely seen in humans and occurs only when a large number of metacercariae are ingested at once
*Fever, tender hepatomegaly, and abdominal pain are the most frequent symptoms of this stage of infection
*Vomiting, diarrhoea, urticaria (hives), anaemia, may be present caused by the migration of the F. hepatica larvae throughout the liver parenchyma
*The larvae penetrate the liver capsule and begin to produce symptoms 4-7 days after ingestion
*Migration and acute phase continues for 6-8 weeks until the larvae mature and settle in the bile ducts

Question 16

2. Chronic Phase

Answer 16

=More common in human
*S/S include biliary cholic, abdominal pain, tender hepatomegaly, and jaundice
*In children, severe anaemia - common result of infection
*Biliary obstruction and inflammation are caused by the presence of the large adult worms and their metabolic waste in the bile ducts
*Inflammation of the bile ducts leads to fibrosis and a condition called “pipestem liver”, (white appearance of the biliary ducts after fibrosis)
*The final outcome is portal cirrhosis and even death

Question 17

3. Obstructive Phase

Answer 17

=Is a heavy and prolonged stage of infection
=Coincides with epithelial changes in the bile ducts due to irritation of the epithelium by the spines and the activity of proline

Question 18

Common S/S of F. hepatica infection
The First stage (prepatent or larval period):

Answer 18

=Abdominal Pain
=Fever
=Backache
=headache
=Chills
=Weight loss
=Urticaria
=Eosinophilia
=Elevation of AST, ALT
=Cough and chest discomfort

Question 19

Common S/S of F. hepatica infection
The second stage (patent or biliary period):

Answer 19

=Intermittent right upper quadrant pain
=Enlarged, tender liver
=Diarrhoea
=Eosinophilia

Question 20

Common S/S of F. hepatica infection
Complications:

Answer 20

Anaemia, cholangitis, biliary obstruction, subcapsular liver hematomas, hemoperitoneum Symptoms

Question 21

Two important complications of Fascioliasis

Answer 21

=Anaemia:
*due to Haematophagous activity of adult flukes (0.5 ml/day)
*infiltration of haemorrhagic tracts by immature flukes
*Initially anaemia is normochromic normocytic and later hypochromic macrocytic

=Hypoproteinaemia (Hypoalbuminaemia):
*Due to destruction of hepatic parenchyma by immature flukes
*Preferential use of amino acids for synthesis of globulin results in hypoalbuminaemia

Question 22

Lab Diagnosis of F. hepatica

Answer 22

=Stool/ duodenal/billiary aspirates microscopy (Sedimentation method)
*Eggs are large, operculated and golden in colour
*Eggs Don’t Show for 4 Months

=Antibody Test
*Can detect 2 Weeks After Infection
*Since eggs don’t show for 4 months, and in the case of ectopic infections where eggs are not present in the stool, serological tests can be used

=Ultrasound
*Visualize Adults in Bile Duct

=CT Scan
*Reveals Burrows in Liver

Question 23

Clinical Diagnosis of F. hepatica

Answer 23

=Diagnosis is based on consumption of a sheep or cattle rearing and a history of consumption of a home grown vegetables or watercress
=Together with some features of fever, eosinophilia, enlarged liver and raised blood transaminase levels

Question 24

Other tests for F. hepatica

Answer 24

=LFTs
*ALT, AST, LDH-L
*ALP and γ-GT
*Albumin, total protein

=Changes in levels of hepatic enzymes such as AST, ALT, LDH-L, are indicators commonly used to monitor fasciolosis progress

=γ-GT is an indicator of damage to bile ducts, and its activity peak follows the peaks of the AST, ALT, LDH-L in vivo

=Increases of ALP and γ-GT activities in post-incubation medium confirm the severe membrane damage.

Question 25

Treatment of F. hepatica infection

Answer 25

=Triclabendazole
*Easier to Use
*1-2 Oral Doses in 24 hrs
*Virtually 100% Effective

=Bithional
*Highly Effective
*Large Dose
*High Cost
*Long Treatment Period

=Surgery

Question 26

Prevention of F. hepatica infection

Answer 26

=Education/sensitization
*Cheapest and Most Cost Effective Way
=Wash Aquatic Vegetables in 6% Vinegar for 5-10 minutes
=Better herding practices
*Keep herds away from aquatic areas
=Moluskicide
*Controls Intermediate Snail Host

Question 27

Fasciola gigantica

Answer 27

=Bigger than Fasciola hepatica (5-7 cm in length)
=More lanceolate
=At anterior end cone is less prominent than F. hepatica
=Cuticle is spiny
=Internal morphology is the same as F. hepatica
=F. gigantica very rarely infects humans

=The life cycle, transmission, morphology, clinical representation and treatment are very similar to those of F. hepatica

=With the use of a scanning electron microscope the surface of F. gigantica appears very rough due to abundant microscopic spines and surface folding

=F. gigantica also has three different types of surface papillae which are used as sensory receptors. T