Phylum Plathelminthes, Class Trematoda

Question 1

Trematodes v Cestodes

Answer 1

Trematoda
Fla/ fleshy leaf like unsegmented bodies
Alimentary canal present but incomplete (w/o anus)
Suckers but no hooks
Sexes are seperate in schistosomes whilst other flukes are hermaphrodiic
Oviparous

Cestodes
Tape like dorsoventrally flattened
No alimentary system
Head have suckers, some w/ hooks
Scolex, neck, proglottids

Question 2

Platyhelminthes v nematohelminthes

Answer 2

Platy
Body - dorsoventrally flattened like leaf/ tape like segmented/unsegmented
Sex - Mostly hermaphrodites except schistosomes in trematodes
Body cavity - absent
Head - cestodes (suckers, some have hooks), trematodes (suckers w/o hooks)
Alimentary canal - incomplete/absent
Hosts - Cestodes (2 hosts except Hymenolepsis -1, and Diphyllobothrium -3), Trematodes (3 hosts except schistosomes - 2)
Oviparous

Nematohelminthes
Body - elongated, cylindrical, unsegmentes
Sex - seperate
Body cavity - present
Head - hooks and suckers absent, well developed buccal capsule w/ teeth/cutting plates in some species
Alimentary canal - complete w/ anus
Hosts - require 1 host except filarial worms (2) and dracunculus (2 hosts)

Question 3

Flukes

Answer 3

Classification - habitat
Blood, liver, intestinal, lung

General characteristics
SIze - 1mm-several cm (M shorter and stouter than F)
2 muscular cup shaped suckers (distomata)
Oral sucker around mouth anteriorly
Ventral sucker in middle ventrally

Question 4

Blood Flukes - Genus Schistosoma

Answer 4

Habitat - Venous Plexi of definite host w/location varying according to species

Definite host - man
Intermediate host - fresh water snail

Dioecious - sexes seperate

Morphology
Forms - ovo, miracidium, cercaria
Ovo - elongated nonperculated brown eggs containgng ciliated embryo (miracidium)
Cercariae -
Adult -
Leaf like unseg body w/ 2 cuplike suckers w/ delicate spines
Birfurcated intestine
M broader than F
Produce elongated nonperculated eggs containing ciliated embryo (miracidium)

Question 5

Fasciopla hepatica

Answer 5

Sheep liver fluke
Cosmopolitan distribution, largest and most common, found mainly in sheep rearing areas

Habitat - liver and bilary passages of definite host

Morphology
Adult - 
- lrg 3cm x 1.5cm, gray/brown
- broader flattened leaf shape
- conical projection ant (oral sucker), ventral sucker posteriorly and rounded posteriorly
-uterus, ovary, testes, vitellaria
- live in bilary tract for many years (5yr sheep, 10 yrs human)
Eggs - 
- large, ovoid, operculated, bile stained
- contain immature larva (miracidium)
- unembryonated when freshly passed
Rediae - 
Cercariae - round head w/ tail

Question 6

Fasciola hepatica

- Life cycle and disease

Answer 6

Definite host - sheep, goat, cattle, man
Intermediate - Snails (encystment occur on aquatic plant - 2nd intermediate host)

Lifecycle

1) Definite host ingest metacercariae encysted on aquatic vegetation
2) metacerciae excyst in duodenum > migrate to bile ducts > adult worm
3) Eggs laid in biliary passages > shed operculated egg in feces
4) Embryo mature in water and miracidium escape > penetrate tissue of intermediate host (snail Genus Lymnaea)
5) Miracidium > 1 - sporocyst > 2 - 1st gen redia > 3 - 2nd gen redia > 4 - cercariae (1-2m)
6) cercariae escape into water and encyst of vegetation > metacercariae

Disease - Fasioliasis
Acute = fever, R upper quadrant pain, hepatomegalt
Chronic phase = biliary obstruct, jaundice, anaemia, cholelithiasis
Diagnosis - detect eggs in stool and aspirated bile, USG, ELISA, ERCP
Prophylaxis - prevent water polution w/ feces and proper disinfection

Question 7

Opistorphis felineus

Answer 7

cat Liver fluke

Morphology

• oral sucker, oesophagus
• no ventral sucker
• testes behind uterus

Life cycle
Similar to Fasciola hepatica but free swimming cercariae encyst in skin/flesh of fresh water fish > metacariae (infective)
> ingested by humans/ cats

Most infections are asymptomatic. Most pathologic manifestations result from inflammation and intermittent obstruction of the biliary ducts.

Question 8

Dicrocelium dendriticum

Answer 8

Lancet fluke - biliary parasite

Definite host - sheep and other herbivores
1st intermediate - snails
2nd intermediate - Ants of genus formica

Morphology

• testes infront of uterus and ovary
• oral sucker at point
• ventral sucker

Lifecycle

1) eggs passed in feces of sheep and ingested by land snails
2) cercariae appear in slime balls secreted by snail > eaten by ants > metacercariae develop
3) Herbivores ingest from accidentally eating ants

Transmission
can be transmitted to humans by eating infected animal