What are common symptoms?
- Condemnation of livers
- Reduced liveweight gains through reduced feed conversion efficiency
- Reduced milk yields
- Reduced fertility
- In severe (but few) cases - death
Youngstock tend to be more susceptible to fluke, however adult cattle do still suffer from the disease. Depending on the level of infection, liver fluke could cost producers between £20-25 per head.
Diagnosis of liver fluke is not simple. EBLEX suggests that liver fluke is often confused with poor nutrition, Johne's disease, salmonellosis or parasitic gastroenteritis. If producers are not normally affected they may not recognise the signs or treat routinely. It is therefore important that if any of the above symptoms are noticed, a vet is contacted.
What causes it?
Liver fluke is caused by a parasite Fasciloa hepatica. Fluke eggs, which are passed in the faeces of a mammalian host, develop and hatch into motile ciliated miracidia - a process which takes nine days at the optimal temperature of 22 to 26o. Development will not occur below 10o. These miracidia have a short lifespan and must come into contact with the host (snail) within three hours.
Development of the parasite continues in infected snails, until cercaria are shed from the snail as motile forms and attach themselves to firm surfaces, such as grass blades, where they become the infective metacercariae. These are then reingested by the final host, completing the life cycle. Once inside cattle, metacercaiae migrate through the gut wall, cross the peritoneum and penetrate the liver capsule and bile ducts.
An adult fluke can be up to 3cm long and can survive in cattle anything between six months to two years. Mild temperatures and above average rainfall provide optimum conditions for fluke development. Wet areas on dry farms are high risk.
How to prevent it?
Dr Phil Hadley from Eblex believes that prevention through pasture rotation is effective against fluke, as this prevents cattle grazing the snail habitat. If possible keep cattle from grazing on wet areas such as pond margins, river banks and marshy ground.
He also says that an appropriate anthelmintic (worming) regime should be used, ensuring products used target eggs, immature and adult fluke and are combined in a programme which mininises wormer resistance.
Control of liver fluke disease should be an important part of a farm health plan drawn up with the farmer's local veterinary surgeon. Monitoring the levels of infection in sheep and cattle using fluke egg counts, abattoir returns and veterinary investigation of ill-thrifty animals is an essential part of successful control.
How to treat it?
A number of products are available for treating fluke in cattle. Flukicides are effective against immature and adult fluke.
Advice for farmers on flukicide usage, particularly with regard to frequency, should take account of the previous farm history, results of abattoir returns, if they are available, and faecal monitoring, tempered with the knowledge that triclabendazole-resistant flukes have been recorded in the UK and Eire.
Where the cattle are out-wintered, for example suckler cows, they should be treated twice. Once during the October/December period to remove the infection that has built up over the summer months and a second time in April or May to remove any fluke infection, which may have been picked up over the winter months. This will help to limit the risk of subsequent egg contamination of the pasture.
Treating cattle seven to 14 days after housing with a flukicide can be very effective in reducing the impact of fluke through the winter says EBLEX. This would then mean that treatment at turnout could be avoided until mid-summer. This might be combined with a worm treatment for convenience, which will help to reduce pasture contamination.
Where possible there may be a benefit in delaying the housing treatment until five to eight weeks after housing to ensure all larval stages of fluke have matured to adulthood and then treating with a flukicide or combine the fluke treatment with worm dose.
Resistance to triclabendazole has been reported in both the UK and Ireland. Where this is suspected discuss the issue with your vet and choose an alternative drug.
In their first year, spring born calves are unlikely to require treatment until housing, and autumn born calves should be treated mid-summer in combination with the routine wormer treatment.
There are no flukicides available with a nil milk withdrawal period, therefore, for routine control treat dairy cows at drying off time.
In urgent clinical cases dairy cows need to be treated and the appropriate withholding period applied. Witholding period information is carried on the product label and datasheet and advice should be sought from a veterinary surgeon.
With potential costs of £20-25 per head or more if an animal dies, it is certainly beneficial for producers to prevent this parasite from infecting cattle. With reports of an increase in cases of liver fluke, farmers are advised to be aware of the problem, even if their herds have not previously been affected and they should take a strategic management approach to preventing and treating cases.
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