PARASITOLOGY - Ruminant Trematodes Flashcards
What is the most significant trematode that affects ruminants?
Fasciola hepatica (‘Liver fluke’)
Remember liver fluke can be transmitted between cattle and sheep
(T/F) Ruminants develop immunity to fasciola hepatica
FALSE. Ruminants don’t develop protective immunity against fasciola hepatica
What is the lifecycle of fasciola hepatica?
- Fluke eggs are shed in the faeces of the final host (10 - 12 weeks after initial infection) onto pasture
- Fluke eggs require moisture and over 10°C in order the undergo embryonisation into miracidia
- After 2 - 4 weeks, the miracidia hatch from the eggs and migrate in thin films of moisture to actively seek a galba truncatula intermediate host
- Over 6 - 8 weeks, the miracidium develop into cercariae within the galba truncatula
- The cercariae emerge from the galba truncatula under the correct environmental conditions (moisture and over 10°C)
- Cercariae migrate onto wet herbage and shed their tails, encysting as metacercariae, the infective stage of fasciola hepatica
- Metacercariae are ingested by the final host when grazing
- Metacercariae are excysted within the small intestine, releasing juvenile fluke
- Over 1 - 8 weeks, the juvenile fluke migrate through the intestinal wall, along the inner surface of the abdominal wall to the diaphragm against which lies the ventral lobe of the liver. The juvenile fluke penetrate the diaphragmatic surface of the liver and migrate through the liver parenchyma to the bile ducts
- Between 8 - 12 weeks of infection, the juvenile fluke develop into adult fluke and feed off blood at the biliary mucosa. At 10 - 12 weeks, the adult fluke begin to produce eggs
What is the prepatent period of fasciola hepatica?
10 - 12 weeks
What is the ideal environment for galba truncatula?
Galba truncatula live in muddy/areas aith slow moving water
When is liver fluke challenge at its peak?
Liver fluke pasture challenge peaks in the autumn
What is acute fascioliasis?
Acute fascioliasis is acute disease as a result of the mass migration of juvenile fluke through the liver parenchyma to reach the bile ducts, which results in extensive parenchymal damage, haemorrhage, severe abdominal pain and sudden death
Seen 1 - 8 weeks into the PPP as this is when the juveniles migrate
(T/F) Acute fascioliasis is only typically seen in sheep
TRUE.
When is acute fascioliasis most prevalent?
Acute fascioliasis is more prevalent in the late summer/autumn
What is chronic fascioliasis?
Chronic fascioliasis is a chronic disease as a result of adult fluke in the bile ducts, resulting in anaemia, submandibular oedema, ascites (due to hypoalbuminaemia), anorexia, immunomodulation and weight loss/ill thrift
Seen 10 - 12 weeks after initial infection
How does immunomodulation secondary to chronic fascioliasis affect livestock?
Immunomodulation increases the risk of secondary bacterial co-infection (particularly clostridial disease)
When is chronic fascioliasis most prevelant?
Chronic fascioliasis is most prevelant in late winter/early spring
Which factors influence the epidemiology of fasciola hepatica?
Local environmental conditions
Presence of galba truncatula
Farming management
What is the economic impact of fasciola hepatica in dairy cattle?
Reduced milk yield and quality
Poor calving to conception rates
What is the economic impact of fasciola hepatica in beef cattle?
Reduced growth rates
Poor fertility
Poor calf weaning weight
Poor feed conversion ratio
Liver condemnation at the abattoir
What is the economic impact of fasciola hepatica in sheep?
Poor growth rates
Poor fertility
Mortality
Liver condemnation at the abattoir
What can be used to monitor and diagnose fasciola hepatica?
Fluke egg detection
Coproantigen ELISA
Serology
Post mortem (PM)
Abattoir feedback
What is indicated by the detection of fluke eggs on a faecal sample?
Detection of fluke eggs on a faecal sample detects liver fluke when egg-laying adults are present, so should be used later in the autumn/winter, when the flukes have had 10-12 weeks to develop into adults
What are the benefits of fluke egg detection?
Fluke egg detection can be undertaken on individual faecal samples or pooled samples, which can reduce costs. Fluke egg detection can be used to both detect infection with adult fluke and to assess treatment efficacy and indicate resistance if used like a reduction test
Why is it so important to be able to differentiate between liver fluke and rumen fluke eggs on fluke egg detection?
Both liver and rumen fluke use the same intermediate host, so both are likely to be present where galba truncatula habitats exist. Correctly identifying these eggs is essential given that adult rumen fluke are not thought to cause any significant health impacts, whereas liver fluke do and require treatment
What is the coproantigen ELISA?
The coproantigen ELISA detects a secretory antigen produced by feeding adult fluke in the bile ducts
What are the limitations of the coproantigen ELISA for diagnosis of fasciola hepatica?
Coproantigen ELISA has limited sensitivity and specificity for diagnosis of fasciola hepatica
What is the main benefit of coproantigen testing for fasciola hepatica?
Coproantigen testing can be used to assess treatment efficacy for fasciola hepatica and indicate resistance if used like a reduction test
How can you do serology testing for fasciola hepatica?
Serology can be done using an ELISA on individual blood or milk (individual or bulk tank) samples to detect antibodies produced following exposure to fasciola hepatica. This usually has to be sent to a lab for results however there is now a penside lateral flow test available to detect antibodies in cattle and sheep using a drop of blood from an ear prick
Be aware the antibodies produce DO NOT provide protective immunity
What are the benefits and limitations of serology to test for fasciola hepatica?
Serology testing is useful as the ELISA can detect antibody levels from two weeks after exposure to fasciola hepatica, and thus is the easliest reliable indicator of fluke. However, the antibody levels will remain high even after successful treatment and in previously exposed older animals, so this test is best used to demonstrate if the animals have been exposed to fasciola hepatica. Monitoring first season grazing animals through regular serology testing can be used to roughly determine when the fluke challenge starts on that particular farm. Once there is evidence of exposure, using fluke egg detection (and maybe coproantigen ELISA) will give more information on the age of fluke present and the likely level of infection. Using the first season grazing animals as ‘sentinel’ animals can guide both the need and the timing of treatments, providing an early warning system before other tests can be utilised.
What is an ideal way to utilise the serology ELISA for fasciola hepatica?
It is useful to take monthly, representative samples from approximately 10 first season, sentinel grazing animals beginning mid-summer to guide both the need and the timing of treatments, providing an early warning system before other tests can be utilised
What are the control methods for fasciola hepatica?
Grazing management
Flukicide drugs
What grazing management can be used to try and control fasciola hepatica infections?
Avoid grazing on high risk pasture (however this can be very challenging as on some farms every pasture can be high risk)
High risk pasture is pasture that is an ideal environment for galba truncatula
What is strategic flukicide treatment?
Strategic flukicide treatment is the treatment of groups of animals at particular times to limit pasture contamination with eggs and hence reduce the risk of parasitism
What is therapeutic flukicide treatment?
Therapeutic flukicide treatment is treating animals with flukicide when they exhibit clinical signs
Which flukicides are available in the UK?
Triclabendazole
Nitroxynil
Closantel
Clorsulon
Oxyclozanide
Albendazole
It is important not to always use the same flukicide and to be aware overuse of any individual flukicide will speed up the development of resistance
Which flukicide have fasciola hepatica started to develop resistance to?
Triclabendazole
Try to avoid if necessary due to developing resistance
What is the spectrum of activity for triclabendazole?
Triclabendazole is targets all stages of the fasciola hepatic lifecycle in an infected animal
What is the only flukicide licensed in dairy cattle?
Triclabendazole
What should you be aware of when using triclabendazole to treat dairy cattle?
Triclabendazole cannot be used to treat dairy cattle when they are contributing to the milk tank, and thus you are limited to being only able to treat dairy cattle for fluke during the dry off periods
What are the benefits of nitroxynil as an alternative flukicide to triclabendazole?
Though nitroxynil doesn’t target the early stages of fasciola hepatica, it does target some of the immuature stages and targets the adults. Furthermore, nitroxynil has an injectable form which is a more practical route of administration
Oral admin - esp. for beef cattle - can be very challenging
However needs to be imported
Which flukicide is sold in combination with ivermectin?
Clorsulon is often sold in combination with ivermectin
Remember closrulon is only licensed in cattle
Why are combined fluke and worming products discouraged?
Combination fluke and worming products are discouraged due to the unlikelihood of animals needing to be treated for fluke and nematodes at the same time of year, risking speeding up the development of anthelmintic resistance
Which flukicide has efficacy agaisnt rumen fluke as well as liver fluke?
Oxyclozanide
Remember rumen fluke doesn’t really have a clinical effect
What should you be aware of if using albendazole as a flukicide?
Albendazole is a benzimidazole but at double dose has a flukicide effect on fasciola hepatica. Be aware you will also be treating for nematodes when using this product
Why is it so important to do monitor and do diagnostic tests prior to treating with flukicides?
The threat of fasciola hepatica varies from year to year, from farm to farm, and even from field to field so it is important to risk assess and test for fluke prior to treatment to determine if treatment is necessary and appropriate, especially as treatment options vary depending on the maturity of the fluke present. Overuse of flukicides speeds up the development of resistance
Which strategic anthelmintic treatments could you do at winter housing?
Can blood sample sentinel animals for serology to determine exposure for fasciola hepatica (can also send for pepsinogen for oestertagiosis in cows). Can also monitor using pooled fluke egg counts. If evidence of exposure, can treat with flukicides at housing and retreat 8 weeks later, or can just delay flukicide treatment 8 weeks into housing
WATCH LECTURE AGAIN TO FIGURE OUT TREATMENTS, USE COWS AND SCOPS WEBSITES TO HELP
