Liver Fluke Disease Flashcards
What type of climate increase fluke numbers?
Warm and wet
How does clinical and sub-clinical fluke disease present differently?
Clinical - sick sheep, sudden death
Subclinical - thin sheep, welfare and production loss
Liver fluke have developed resistance to?
Triclabendazole
How does rain affect the epidemiology of liver fluke?
- Increases snail habitats
- Allows the development of fluke eggs
- Dispersal of cercariae from snails
What must the temperature be for miracidia to develop in eggs?
More than 10 degrees
UK conditions for fluke and eggs are at what times of the year?
Between spring and early winter
In the late summer, what takes place in the fluke cycle?
Large numbers metacercariae released from snails onto pasture
What is the consequence of large numbers of metacercariae being released from snails in the late summer?
Acute facsiolosis in sheep in autumn
When does Chronic fasciolosis occur?
Winter and spring as less metacecariae are ingested
Describe the summer infection of fluke
- in spring, eggs are excreted from infected sheep/overwintered eggs
- Miracidia infects snails
- in summer/autumn - cercariae and metacecariae are shed by snails
- Winter disease in sheep
Describe winter infection of fluke
- In autumn snails infected with miracidium hibernate
- in late spring, metacecariae infect sheep
- early summer acute disease of sheep
What are the signs of acute fluke disease?
- Severe haemorrhage due to migration of immature stages through the liver
- Sudden death
- Weakness
- Pale
- Dyspnoeic
Describe the pathogenesis of chronic fluke disease
- Smaller numbers metacercariae ingested over autumn and winter
- Blood feeding adults in the bile ducts
- Haemorraghic anaemia, hypoalbuminaemia
- Hepatic fibrosis and cholangitis
What are the clinical signs of chronic fluke disease?
- Anaemia
- Weight loss
- Sub mandibular oedema
- Weight loss
- Enlarged liver
- Secondary clostridial infection - Black’s Disease
How can fluke be diagnosed?
- Faecal egg counts
- Coproantigen ELISA
- Serum ELISA antibody test
What is a possible disadvantage of diagnosing fluke using a FEC?
False negatives in early infections and acute disease
How long post infection do FEC detect fluke?
12 weeks
How long post infection do coproantigen ELISA tests detect fluke?
10 weeks
How long after infection do serum ELISA antibody tests detect fluke?
2-4 weeks
Which drug against fluke can kill all stages?
Triclabendazole - but there is some resistance
Name 2 alternative drugs that can be used for fluke
Albendazole
Closantel
How can managing the environment help to control fluke?
- Assess farm for snail habitats and fence off - Muddy, wet fields, pooling of water, blocked ditches, rushes
- Improve the pasture - Drain, improve, or avoid at least late summer autumn
- Reduce stocking density in autumn
How/in what ways can fluke be monitored on farm?
- Have a guide to timing doses
- Use forecasting
- Post-mortem any animals that die of sudden death
- Assess how well the drugs are working
Describe how targeted drug treatments can be used to target fluke whilst helping prevent resistance?
- Use Triclabendazole in the autumn against immature stages
- Use Closantel in the winter against immatures and adults
- Use albendazole in the late spring against adults
When could additional treatments be given to high risk farms/high risk years?
Additional doses in November- immature stages (TCBZ)
Additional doses in June (for winter infection of snails) immature stages as well (TCBZ)
How can fluke drug resistance be prevented?
- Rotational use of drugs
- Only use triclabendazoles when necessary i.e. autumn
- Test for triclabendazole resistance
How can you test for triclabendazole resistance?
Composite Faecal Egg Count Reduction Test
Why is spring dosing against fluke important?
Against adults - prevents egg output and summer infection of snails
