Revision Liver Trematodes Flashcards
Outline different types of Fascioliidae?
Fasciola hepatica (30 mm)
Fasciola gigantica (75 mm)
Fascioloides magna (100 mm)
+ many others
Outline the general fluke lifecycle?
Outline fascioloidosis in different hosts?
Cattle/Camelids : Pathogenicity usually low, but liver may still be condemned at slaughter. (eggs not passed) [dead-end host]
Sheep/goats : Few pathogens can cause a very serious disease due to the extent of migration. (eggs not passed) [aberrant host]
Deer : Adults become encapsulated, usually no pathology. (Eggs are passed)
Patent infection in deer suggests; the true host.
Discuss immune response to trematodes in goats?
- Immune response in goats
- Increase in blood eosinophils.
- Increased eosinophil and plasma cell infiltrate in tissues in which flukes have migrated.
- Serum IgG specific for the E/S products of F. magna detected in sheep and goats.
Otherwise very few immunological studies done with this species.
How are liver trematodes diagnosed?
- Eggs in faeces via McMaster. However, in some cases none will be seen e.g. Fascioloides in sheep and cattle.
- ELISA (available for some trematodes). Plasma enzymes which signal liver or bile duct damage e.g gamma- glutamyltransferase(GGT)
- Generally on condemnation of liver or following necropsy.
Outline treatment for fluke diseases?
Discuss fasciola gigantica?
- Chronic fascioliosis in cattle, Buffalo less susceptible.
- Acute often fatal disease in sheep.
- Severe economic loss in weight gain and milk throughout Africa and Asia.
- Life cycle the same as F. hepatica but snail species may be different.
Discuss buffalo and fasciola?
- Pre-patent period in cattle has been reported at 64 days but in buffalo this is about 95 days.
(longer incubation period)
- Although infection rate in both cattle and buffalo is similar pathology in cattle is greater.
(less pathology)
- Eosinophilia delayed in buffalo compared to cattle which may account for a more rapid pathological effect in cattle.
(less immune response)
Look at this Dicrocoelium dendriticum?
(Lancet/small/lesser fluke) 6 mm –1.0 cm
What is the lifecycle of Dicrocoelium dendriticum?
Discuss what Dicrocoelium dendriticum does in the host?
In the host (usually ruminant)
- Usually sub-clinical but can cause disease during very heavy infections.
- If clinical then usually sheep rather than cattle.
- Does not penetrate the liver capsule, tissue or gut wall as with F. hepatica.
- Anaemia, oedema, liver fibrosis and hepatic damage may occur in heavy infection.
- Little is known about the immune response, antibody responses have been seen against adult protein secretions.
Discuss epidemiological factors of Dicrocoelium dendriticum?
- Eggs quite resistant (can survive many months on pasture).
- May lead to exposure of land snails and ants to large number of eggs.
- Wild life may act as reservoirs.
- Resistance to Flukicides.
Discuss fasciola hepatica?
Fasciola hepatica
- Known as ‘Liver fluke’
- Hepatic parasite of ruminants
- Extremely common in the UK
- Prevalence increasing with time
- Spread of disease to previously unaffected areas
- Responsible for significant economic loss
- Does have public health implications
Discuss the lifecycle of fasciola hepatica?
F. hepatica has a definitive ruminant mammalian host and an intermediate molluscan host
How is Fasciola hepatica diagnosed?
- Gold standard is the faecal egg count (FEC)
- Standard sedimentation technique followed by examination under microscope.
- Eggs are 140 μm x 80 μm in size.
- Additionally clinical exam can reveal some signs of infection, e.g. Body score, diarrhoea
- Serum concentrations of liver enzymes AST, GGT, GLDH are indicative of infection.
- Differential blood count -eosinophilia
- Progress in antibody based diagnostics –Bio-X diagnostics ELISA kit –Cathepsin L1 based kits
What is the clinical presentation of fasciola hepatic infection?
Acute, Sub-acute, Chronic.
Dependent on a number of factors:
- Dose of metacercariae
- Rate of uptake of metacercariae
- Final worm burdens
- Animals are routinely treated?
- Parasites are drug resistant or not?
- Animal condition at onset of infection.
How does acute fasciola hepatica infection present?
- Sudden death between Aug-Oct (time required to pick up large enough number of metacercariae from pasture.
- Signs of liver damage including haemorrhage.
- Non-clinical diagnosis –liver damage + many larvae bile ducts and gall bladder (liver enzymes in plasma/ albumin and globulin conc.)
- Also think about epidemiology. Rainy/dry year
How does sub-acute fasciola hepatica infection present?
- Rapid loss of body condition
- Poor fleece condition
- Depression
- In-appetance
- Inability to stand
- Non-clinical diagnosis by liver enzymes/protein conc. in plasma and immature flukes in bile duct and gall bladder (again need to consider epidemiology)
- Death may occur in Autumn but fatal sub-acute fasciolosis usually occurs in Winter.
How does chronic fasciolosis present?
- Very poor body and fleece condition
- Bottle jaw may be apparent
- Death may occur during lambing
- Non-clinical diagnosis -eggs in faeces and adult flukes in bile duct
Describe liver pathology in F hepatic infection?
- Juveniles migrate through liver until they locate the bile ducts where they mature
- Severe disease occurs when many ME are ingested over a short period of time resulting in liver haemorrhage/anaemia
- Usually small amounts are ingested over longer period of time, liver function compromised by fibrosis
Discuss infectious necrotic hepatitis (black disease)?
- Occurs in cattle and sheep.
- Animal ingests spores of Clostridium novyi in soil.
- Non-pathogenic in oxygen rich environment
- Within the liver, bacteria multiply rapidly in area of necrosis caused by migrating flukes
- Bacteria produce tissue toxins which cause severe damage to liver
- Usually no signs-animal suddenly dies
- This can lead to misdiagnosis as acute fasciolosis
What is the treatment of F. hepatica?
- If fluke is present treat with triclabendazole in Sept/Oct & again in Jan if FEC is positive.
- Treat against adult only stages in May/June preventing pasture contamination.
- Do not use the same treatment at Sept/Oct, Jan, or May/June.
- Treat additionally if particularly wet years.
- Isolate & treat all new animals bought from outside.
- Inefficient/wasteful use of triclabendazole means drug resistance is a major concern in Ireland & UK.
- Fence off wet areas (e.g. pasture running to rivers and streams)
- Increase soil drainage.
- Control of wildlife reservoirs of Fasciola –where possible & legal!
What is the epidemiology of F. hepatica?
- In Europe almost exclusive snail host is Lymnaea truncatula (common pond snail)
- In other countries other Lymnaea species are important.
- Snail habitat crucial to spread therefore wet conditions ideal.
- Climate change and drug resistance believed to be important in UK spread.
