1. Flukes. Fasciolosis. Fascioloidosis Flashcards
What 3 phylum of parasitic helmints do we study?
- Flatworms Platyhelmintes (include flukes and tapeworms)
- Roundworms Nematoda
- Thorny-headed worms Acanthocephala
Another name for fasciolosis. Where is it localised in the world?
Liver fluke disease, hepatic ditomatosis, liver rot
Worldwide in grazing animals, most commonly in a chronic form without characteristic clinical signs
Fasciolosis is caused by ___ ?
- Fasciola hepatica - common liver fluke (2-3cm) - temperate areas
- Fasciola gigantica - large liver fluke (2-10cm) - (sub)tropical regions
Fasciola hepatica
- leaf-shaped
- up to 5 cm long, 1 cm width
- conical anterior end
- tegument with spines (to anchor itself)
- brownish-grey
- 2 suckers: apical and ventral
- longevity: several years
Site of Fasciola hepatica
Bile ducts (gall bladder)
Rarely in other organs (e.g. lungs - ectopic sites)
Intermediate hosts of Fasciola hepatica
Amphibious freshwater snails of the genus Lymnaea (Galba)
- Galba (Lymnaea) truncatula - dwarf pond snail in Europe only !!!
- Lymnaea tomentosa and Lymnaea columella in Australia
Life cycle of Fascila hepatica
Indirect, pp period is ~10 weeks
- Adult worms produce large (120-150 micrometers) eggs which are shed with host’s feces
- Zygote containing egg develops to a ciliated larva (miracidium) in water usually within 2 weeks
- Larva hatches and swims in water to find and penetrate into freshwater snail
- In the body of snail the first larva turns to a bladder-like sporocyst
- In the cavity of sporocyst a third larval form develops by asexual budding, so called paedogenesis
- The third larval form, called redia has a mouth and a blind sac of intestine and actively consume the tissues of the snail host. Depending on the size and nutrition of the snail, from the first generation of mother rediae several generation of daughter rediae can come into being inside of the same intermediate host
- After some time the cercaria develops inside the body of the redia. Cercariae have long tail and two suckers
- After rain the mudflat where the snail live becomes wet and cercariae actively swarm out of the snail and swim for some minutes to find solid surface
- Cercariae attach themselves to vegetation, shed their tail and encrypt a metacercariae
- After ingestion (cyst walls will be removed by digestion) be the final host the juvenile fluke (marita) penetrates the intestine and migrates to the liver via abdominal cavity
- Migration in the liver parenchyma takes 4-6 weeks
- Settling and reaching maturity in biliary ducts
- miracidium -> sporocyst -> redia -> cercaria -> metacercaria (PP period is approx 10 weeks)
Longevity of Fasciola hepatica
Several years (in sheep up to 11 years)
Morphology of Fasciola hepatica eggs
- oval
- one operculate
- golden yellowish ! (that’s how its differentiated from rumen flukes - those are whitish)
- 130-145 micrometers
- with zygote
General morphology of flukes
unsegmented parasitic worms with 2 suckers* and a branching intestinal canal
Their larvae always develop in molluscan hosts first
Acute fasciolosis (in sheep)
- in short amount of time huge amount of metacercaria is consumed
- no characteristic clinical signs!
- sudden death may occur at 2-5 weeks after massive infection
- no eggs in feces!!!
How to diagnose acute fasciolosis?
Only necropsy
No eggs in the faeces!
Enlarged, haemorrhagic liver with traumatic tracts of migrating young flukes
Subacute fasciolosis
- massive, longer period of metacercaria intake
- loss of appetite and weight, progressive haemorrhagic anaemia, peritonitis, enlarged liver, cholangitis, liver fibrosis, death
- anaemia normocytic and normochromic type, later hypochromic, macrocytic due to increased iron loss
Chronic fasciolosis
- moderate prolonged intake of metacercaria
- chronic cholangitis and hepatic fibrosis
- oedema under the jaw (‘bottle jaw’)
- dysproteinaemia caused by an increase in the gamma-globulin concentrations in the serum and by the loss of albumin; hypoalbuminemia, eosinophilia and elevated liver enzymes.
Diagnosis of fasciolosis
- detection of the eggs (in acute fasciolosis there are no eggs in feces) - the specificity is high but low sensitivity, volume of feces is important!
Eggs of rumen flukes are very similar (colour!) - Serology
- ABs in serum or milk -> no differentiation between active and past infections
- coproantigen from faeces (from 2-5 weeks post infection) - Blood parameters (AST, GLDH elevated in (sub)acute, GGT in chronic; eosinophilia, anaemia, hypoalbuminaemia)
- PCR
- Necropsy
Enlarged, haemorrhagic liver with traumatic tracts of migrating young flukes; acute, traumatic, haemorrhagic hepatitis; cholangitis, liver cirrhosis, presence of immature and early mature flukes.
