Extended liver fluke season and climate change

Fascioliasis

An important stage of the Liver fluke life cycle takes place in mud snails and requires wet and warm conditions (above 7 – 10°C) during the summer months. Over the last couple of years unseasonal weather has seen these conditions well into autumn and winter. This means that sheep and cattle are still being infected later in the season and more frequent testing and treatment may be required.

Fascioliasis can have a serious financial impact on a sheep farm with immediate losses up to 10 per cent caused by acute/subacute disease. Chronic disease could half profits by reducing lamb crop and increasing ewe mortality. Lack of treatment in cattle will lead to reduced growth and yields and discarded milk if treatment is no targeted.

We recommend testing your sheep and cattle for the presence of Liver fluke. Treatment needs to be targeted at your flock/herd and will vary from farm to farm. Please discuss your individual requirements with your vet to develop a treatment plan for the coming months.

Liver Fluke

Liver fluke has a complicated life-cycle involving a tiny mud snail which is the intermediate host responsible for infection on pasture.

Traditionally Liver fluke was thought to be very regional however movement of stock, changing weather patterns and ground conditions have increased the fluke risk to the whole of the UK. Lancashire has a climate that favours the snail and therefore also favours fluke transmission and increase fluke risk.

A move to housing dairy cows all year round may be thought to remove the risk of Liver Fluke from the herd, but positive bulk milk samples are still reported from zero grazing herds! Where heifers are turned out they may become infected and maintain a reservoir of infection. Where fluke is identified these animals should receive appropriate treatment. Sheep, deer, hares, geese and horses can all carry fluke and complete the lifecycle outside of the snail.

New research by the Mordun Institute has found that Metercerariae (the stage passed by the mud snail that are ingested by cattle) are very persistent and this stage of fluke can survive in silage. Heat and pH are thought to be involved in killing off the Metercerariae in most cases, but in less well fermented silage, wet silage and less acidic silage this is less so. With this in mind poorly made silage, later cuts and big bale silage pose the highest risk. Last year’s silage crops were certainly made in challenging conditions.

Further investigations into housed youngstock infections, egg survival and spread in slurry are ongoing but if you have history of fluke infections in housed cattle submitting further investigation may be useful.

Liver fluke herd

Even in herds that are housed 365, there is still a risk of liver fluke. There is an inexpensive bulk milk test available, some interpretation is needed if first lactation heifers are introduced after grazing. However there is a test available (the coproantigen test) that will test for current infection to differentiate this. It is also thought that Liver fluke can survive in cattle for 2 years.

Due to the complex life cycle and products available to treat lactating cattle, treatment is often targeted at dry cows often making it difficult to treat the correct animals at the correct stage of infection. Creating a testing and treatment plan with your vet is the best course of action on an individual farm basis. Care should be taken to select appropriate treatment product for dairy cattle, flukicide residues are increasingly being detected in bulk milk samples.

liver fluke treatment plan

Liver Fluke

The NADIS liver fluke forecast for the end of 2017 held true with many flocks in Lancashire being exposed to a heavy burden of fluke.

Both acute fluke and sub- acute fluke were prevalent so treatments administered were targeting immature fluke. The products used were either triclabendazole and/or closantel and/or nitroxanil depending on the flocks’ history. While these products are very effective, repeated use will inevitably increase the risk of resistance, to the active ingredient.

To limit resistance, other flukicidal products should be considered, now that the main risk period is coming to an end. Paddocks grazed over the autumn and winter will now carry a much lower burden of the infective metacercariae so treatments can be targeted at the adult flukes (Chronic fluke) that have survived. Targeting the adult fluke at this time of year will reduce the number of fluke eggs shed onto pasture before the mud snails become active.

If you would like anymore information, please contact us.

Liver Fluke

The NADIS Liver Fluke forecast uses veterinary surveillance combined with weather reports to predict the risk of disease over the coming months. ‘There was an increase in diagnoses of liver fluke disease at the start of this year and the risk of acute fluke is forecast to be high in some parts of North West England and North Wales. It is therefore likely, that treatment for acute fluke will be necessary during October on farms in these regions, especially where there is a history of liver fluke disease.’

Fasciolosis is a common parasitic disease of both cattle and sheep in the UK, caused by Fasciola hepatica and is estimated to cost the cattle industry £23 million annually.

In cattle, infection is more commonly encountered in beef cows grazing poor wet pasture but disease can be seen in dairy cattle especially after summering cattle, most likely bulling heifers, away from home on infested pastures.

Liver fluke lancashire farm

Life cycle

The life cycle involves a snail host whose activity and availability require adequate moisture and a suitable ambient temperature during the summer months. Recent wet summers (2015) have been ideal for this complicated fluke lifecycle by supporting large numbers of snails in wet habitats. Cerceriae are released from snails between August and October which develop- into the infective metacercariae, which can survive on pasture for several months to infect grazing cattle.

Clinical Signs

Dairy Cows – In severe chronic infestations, dairy cows show reduced milk yields and poor fertility together with excessive weight loss. Many show chronic diarrhoea.

Beef Cows – The clinical signs are similar to those encountered in dairy cows but can be especially severe in spring-calving beef cows where liver fluke exacerbates the metabolic demands of advanced pregnancy in cattle on marginal winter rations. This results in the birth of weakly calves to cows with little milk, causing high perinatal losses. Severely affected cows may become debilitated with an increased incidence of metabolic and infectious diseases at calving.

Twin-bearing cows show the most severe signs due to the high demands of two foetuses. Unlike infestation in sheep, peripheral oedema is a less common finding with chronic fasciolosis in cattle. Severe infections may cause anaemia.

Bulls – Infested bulls show similar clinical signs as cows such as chronic weight loss and diarrhoea.

Fattening cattle – UK slaughter plants are reporting increasing numbers of liver condemnations due to fluke damage in 12 to 18 month-old fattening cattle where reduced live-weight gains were not suspected by producers presumably due to low-moderate infestation levels.

Sheep

Signs of acute fluke disease

Sheep with acute fluke infestation may simply be found dead without prior signs of illness therefore it is important to have all sudden deaths investigated to allow immediate preventive measures.
Post-mortem examination is essential to establish a diagnosis of acute fluke.
Less severe clinical signs include reduced grazing, rapid weight loss, weakness, abdominal pain, anaemia, and slow to gather.

Differential Diagnoses

Weight loss and chronic diarrhoea in individual cattle will also be investigated by your veterinary surgeon for paratuberculosis and salmonellosis. Chronic liver fluke and paratuberculosis have been reported in the same animal. Other causes of chronic weight loss in adult beef cows could include other bacterial causes such as pyelonephritis, vegetative endocarditis, chronic mastitis, and chronic suppurative pneumonia.

Inadequate nutrition generally presents as a whole group/herd problem of poor production and weight loss during the late winter months in beef herds with diarrhoea an uncommon finding unless poor quality silage is fed.

Fluke Control Measures

Liver fluke disease can be largely controlled by effective drugs administered at the correct time as part of the flock health plan.
Wherever possible, reduce the risk of fluke infection by keeping sheep away from potentially contaminated, poorly-drained areas of the farm.
Triclabendazole (TCBZ) is the drug of choice in cases of acute fluke disease because it is effective against very young immature fluke stages.
However, advice will also be needed where TCBZ-resistance has been previously suspected on farms and the effectiveness of fluke treatments monitored.
The coproantigen ELISA test can be used to monitor TCBZ efficacy two to three weeks after dosing, and farmers should contact their veterinary surgeon for further advice where drug resistance is suspected.
Later fluke treatments could use closantel or nitroxynil especially if TCBZ- resistance is suspected or proven on the farm.
Where these drugs are used then accurate dosing is essential as toxicity is possible.
Also, ensure all lambs are vaccinated against clostridial diseases because migrating flukes predispose to Black disease.

If you’re concerned about Liver Fluke and would like more information, feel free to contact us.