Dose now to control Liver Fluke
According to a Teagasc cattle specialist the risk of liver fluke disease is expected to be high throughout the whole country over thee coming months. The forecast takes account of the heavy rainfalls that have characterised four of the last five grazing seasons
“Cattle develop only weak immunity to liver fluke and although adult cattle are more resistant than younger stock, all cattle including suckler cows are at risk and should be treated,” explained Teagasc’s Liam Fitzgerald.
Just now and over the next few weeks is the ideal time to treat cattle for fluke. Animals pick up the infective fluke larvae (metacercariae) from the grass, so therefore once cattle are housed they cannot pick up any new infection.
“Treatment after housing is obviously a critical time to control fluke disease and also a good strategic method of limiting the spread of the disease on the farm,” he further explained.
“The timing of treatment after housing depends on the type of drug used. Some drugs will not kill the very early stage of the infective “immature” fluke so you should wait until the fluke have matured to a susceptible stage before treatment with such drugs.
“The infective stages of fluke are “early immature”, covering the period of about six weeks between ingestion of the young flukes off the grass to their arrival in the liver. The “immature” stage lasts up to another six weeks while the flukes are burrowing through the liver and feeding heavily on liver tissue. The “adult” stage refers to flukes of 10-12 weeks old that have made their way through the liver where attach themselves to the bile ducts and feed on blood.
“Here they produce eggs that carry on the life cycle when shed in the dung on to pasture. Heavy infection causes anaemia and loss in performance. The loss in performance has been estimated at 20kg-30kg on a weanling or store animal over the winter. Effective housing treatment not only prevents performance losses but reduces the amount of pasture contamination with fluke eggs in spring.”
The Teagasc representative went on to point out that the most effective drugs are those that kill the early immature stages as well as the adults. In this way, effective treatment is given before significant liver damage and loss of performance occurs and before the flukes get to produce eggs, which is important in the case of out-wintered stock.
Products containing triclabendozole are effective against the early immature stage and can be given at one and two weeks after housing. Products containing closantel and nitroxynil can be given about six weeks after housing when any larvae picked up prior to housing will have reached the immature stage that is the susceptible stage for these drugs. Products containing rafoxanide may not kill fluke less than eight weeks.
In most cases, the next two weeks is the appropriate time to treat cattle that were housed in late October/early November and have not been treated already.
The Teagasc representative concluded: “Check with your vet in relation to the likely incidence of the disease on your farm and the most suitable treatments. Vets will have a good knowledge of the incidence and severity of the disease in their work areas and are in a position to give specific advice. Combination doses that control type II worms but adult fluke only are not the best choice at this time of the year.
“The newly introduced injectable Closamectin, which controls immature fluke and type II worms, is suitable for young stock that have not already got a worm dose at housing and have been indoors for about six weeks.