Trematodes

Question 1

What are trematodes?

Answer 1

• Flukes
• Unsegmented parasitic worms
• 2 suckers
• A branching intestinal canal
• Bilat. flattened (except Schisostoma)
• Hermafrodites
• Larvae develop in molluscan hosts first

Question 2

Important trematodes

Answer 2

• Liver flukes - Fasciola
• F.hepatica - common liver fluke
• F.magna - great american liver fluke
• F.gigantea
• Rumen flukes: Paramphistomum+Calicophoron
• P.cervi
• P.ichikawai
• C.daubneyi
• Lancet flukes - Dicrocoeliosis dendriticum
• Blood flukes - Schistostoma spp. (Europe: S.turkestanicum, Human: S.mansoni, S.haematobium, S.japonicum)

Question 3

Liver fluke

1. IM host
2. Final host
3. Detection
4. Place of infection

Answer 3

1. Lymnoid snails - mainly Galba Truncatula (freshwater snail)
2. i) sheep, goat, rabbit, hare ii) cattle, deer iii) horse, pig, dog, cat, human
3. Flotation or sedimentation (eggs present in feces after 6-12w)
4. Acute: young flukes in parenchyme. Chronic: biliary ducts

Question 4

Rumen fluke

1. IM host
2. Final host
3. Detection
4. Place of infection

Answer 4

1. P.: planorbirds, C.: Galba Truncatula
2. P.cervi: sheep+goat, P.cervi+ishikawai: wild Ru, C.: cattle
3. Flotation or sedimentation
4. SI –> Forestomacs

Question 5

Lancet fluke

1. IM host
2. Final host
3. Detection
4. Place of infection

Answer 5

1. First: landsnails, second: ants
2. sheep, goat, cattle, wild Ru, rabbit, hare, rarely pig and horse
3. Flotation
4. Hypertrophic biliary ducts of liver

Question 6

Life cycle of liver fluke

Answer 6

1. Adult worms produce non-embryonated eggs shed with host´s feces
2. Eggs becomes embryonated in water
3. Zygote containing eggs develope to ciliated larvea - Miracidium
4. Miracidium finds IM host - snails, and in the body forms 2nd larvae - sporocysts -> 3rd larva - rediae (paedogenesis, inside sporocyst) -> cercaria (in body of redia)
5. Cercaria swims out of snail into water, and becomes metacercaria in vegetation
6. Metacercaria is ingested by definitive host, excyst in duodenum and becomes juvenile fluke
7. Juvenile fluke penetrates intestines and migrates to liver via abdominal cavity (4-6 weeks) - praepatent period ca. 10 weeks
8. Mature into adult flukes in biliary ducts

Question 7

Life cycle of rumen fluke

Answer 7

Similar to liver fluke, but:

• IM host may be other than lymnaeid snails
• Never leaves intestinal tract on the way to forestomachs
• Praepatent period is longer - 16-18 weeks

Question 8

Life cycle of lancet fluke

Answer 8

Similar to liver fluke, but:

• Eggs shed from host already contains miracidium
• No redia stage
• Cercaria with long tail and sharp spine are released from snails with expelled mucous on plants
• Infects another IM host – ants and here turns to metacercariae
• Ants are accidentally ingested by grazing animals
• Juvenile flukes goes to liver through biliary ducts
• Preapatent period approx. 7-10 weeks

Question 9

Difference between the eggs

Answer 9

• Liver fluke egg: yellow, thin shelled, with a cap (operculum), 120-150 um, oval,
• Lancet fluke eggs: hard-shelled, thicker and lighter than liver fluke, miracidium inside has two eye-like excretory cells (only seen when mature)
• Rumen fluke egg: 120-180 um, colorless, oval, thin-shelled with a cap

Question 10

Intermediate host

Answer 10

• Liver fluke: mainly Galba Truncata in Europe and other freshwater snails in other parts of the world
• Rumen fluke: Galba Truncata for Calicophoron species, planorbirs snails for Paramphistomum species
• Lancet fluke: 1st small landsnails, 2nd ants in Formica genus

Question 11

Definitive host:

Answer 11

• Liver fluke: i) sheep, goat, rabbit, hare ii) cattle, deer, mouflon, buffalo, camel iii) dogs, cats, horses, swine, humans
• Rumen fluke: ruminants: cattle for Calicophoron, wild ru for Paramphistomum, sheep and goat for P.cervi
• Lancet fluke: sheep, goat, cattle, wild Ru, rabbit, hare, rarely pigs and horses