Fluke Flashcards
What are the names of the common liver fluke?
Fasciola hepatica
Fasciola gigantica
What are the types of rumen fluke?
Paramphistomum spp
Calcicophoron daubneyi
What are the types of lancet fluke?
Dicrocoelium Dendriticum
What are the typical characteristics of flukes?
Indirect life-cycle
Dorso-ventrally flattened
Hermaphrodite
No body cavity
Tegument
Where is fasciola hepatica and gigantica found?
Hepatica- UK and Europe, Austrailia, South America, High altitude tropics
Gigantica- Hot and humid tropics
What impacts on animal production does Fasciolis cause?
Growth rate
Milk yield
Wool and fibre
Liver Condemnation
Disease- morbidity and mortality
Describe the lifecycle of F. hepatica
- Undifferentiated eggs shed in faeces from definitive host
- Over 2-4 weeks they develop within the eggs first showing an eye spot into a miracidium through operculum- has to be over 10 degree
- Miracidium uses cillia to swim to snail within 24 hrs otherwise die
- Micacidum burrow into snails foot and shed their outer layer and become sporocyst
- The sporocyst undergo clonal expansion to a rediae to a cercariae
- 1 miracidia = 600 cercariae
- After 6 weeks the parasites break out of the snail and encyst by losing their tale after attachment on pasture to a metacercariae
- Metacerciriae are ingested and are newly excyted juvenliles (leave the cyst)
- NEJs pass through peritoneal cavity from duodenum to liver- 6-8 days
- Imature migratory flukes migrate through liver using proteolytic enzymes to the bile duct and grow in size and become sexually mature adults
What are the different diffinitive mammalian hosts?
Ruminants
Camelids
Wild animal reservoir
Horses- dont develop patent infections
Humans
What are the intermediate snail hosts of F. hepatica and F. gigantica?
F. hepatica- amphiboius mud snail- Galba truncatula in UK
F. gigantica- water snails
How do adult fluke move and hold their position?
They use suckers and spines
What are the two forms of the disease Fasciolosis?
Acute and Sub-acute
Type of disease determined by the number of metacercariae ingested and the time period over which they are ingested
What causes acute fasciolosis and when is it seen?
Immature/juvenile migrating flukes with large numbers
Only ususally occurs in sheep in UK
October-december
Multifocal necrotic or haemorrhagic tracts throughout the liver
Describe the pathogenesis and clinical signs of acute fasciolosis?
Pathogenesis-
Migration of immature flukes through the liver parenchyma
haemorrhagic tracts
Inflammation
Liver enlargment
Fibrosis
Clinical signs-
Sudden death
weakness/dullness
abdominal pain
Anaemia
What causes chronic fasciolosis occur and when does it occur?
Occurs in sheep and cattle
Low numbers of metacercariae ingested over long period of time
Adult fluke in bile ducts
Disease in late winter/early spring- Jan- March
Describe the pathogenesis and clinical signs of chronic liver fluke
Pathogenesis-
Adult flukes feeding on blood in bile ducts
Spines on the tegument irriate bile duct walls
Hyperplasia of bile ducts
fibrosis and calcification (cattle)
cholangitis
Clinical signs-
Progressive weight loss
anaemia
sub- mandibular oedema
ascites
What is sub-acute fasciolosis?
Sheep ingest metacercariae over a long period of time
Disease casued by immature/juvenile and adult flukes
Clincial signs- rapid weight loss, anaemia
How long does it take for the liver fluke life cycle?
6 months
What are the factors that affect the epidemiology of liver fluke?
Snail and snail habitat
Temperature- 10-25 degrees
Moisture
Overwintering-
- Carrier animals
- Eggs on pasture
- Metacercariae on pasture
- Fluke stages within snail
What happens in spring for liver fluke?
Low snail population at first
Eggs on pasture
Increase in temperature
snail populaiton increases
Eggs develop (2-4 weeks depending on temp)
Miracidia infect snaila
What happens in summer with liver fluke?
Summer infections of snails
Asexual reproduction- sporocyst- rediae- cercariae
Three wet months-
Large numebers of cercaridae released on pasture in september
Large numbers of metacercaridae on pasture and ingested
acute disease 2-6 weeks
Cool dry summer
Fewer metacercariae produced
released gradually from snails between September and November
chronic disease in winter and early spring the following year
How is liver fluke diagnosed at an individual level?
Clinical signs (sudden death, weight loss anaemia)
Season (autumn and winter)
Farm history
PM examination
How is liver fluke diagnosed at a farm level?
Compostie faecal egg counts (10 animals/group)
Bulk tank milk ELISA
Abbatoir returns
What diagnostic tests are availible for liver fluke?
FEC- fecal egg counts
High specificity
Composite samples
Poor sensitivity, labourious
Only detects patent infection
Copro-antigen ELISA
similar to FEC- detects patent infection
Antibody detection ELISA
Milk or bulk tank milk as well as serum
Detects exposure not necessarily current infection
How is liver fluke best controled?
Disease forecasting
Grazing managment
Elimination of snail habitat
Drug prophylaxis- no residual activity
Triclabendazole- effective against all stages of fluke but resistance in the UK
Others are effective against late immature and adult flukes
