Farmers should be taking action now to help control liver fluke this autumn, as wet weather sees cases escalating already, according to Wiltshire vet Keith Cutler.
And it’s not just usual risk areas next to rivers and standing water where farmers should take action, but overflowing water troughs, wheel ruts and rain ponds, which also provide the perfect habitat for the intermediate host, the mud snail, he warns.
Mr Cutler, from Salisbury, says cases are also appearing in low-risk areas. “It is usual to see cases in water meadows, but even the chalk downlands are suffering because of the amount of ground water from persistent rain.
NADIS says fluke cases in western Scotland may reach epidemic levels, with Wales, north-west and south-west England, Northern Ireland and Scotland also at high risk.
Several reasons account for the rapid fluke increase this year. Wet and mild weather has increased fluke habitats, allowing fluke to thrive and spread to previously unaffected parts of the country. This, coupled with previously high incidence, means fluke and snail numbers started from higher levels this year.
Mr Cutler says there may be more acute cases this year due to increased numbers of fluke. “Ingestion of large numbers of fluke over a short period can lead to anaemia and often sudden deaths in animals where sufficient numbers of fluke are present.
“Chronic fluke disease is when one or two larvae have penetrated the liver and has more easily identifiable symptom such as weight loss, anaemia and bottle jaw.”
Cumbrian vet David Black has also seen a rise in fluke antibodies in dairy herds through bulk milk samples. “Although we haven’t seen many clinical cases, more than 60% of dairy herds have tested positive for fluke antibodies in bulk milk. Inevitably this may be knocking 5-10% off yield, particularly when you consider liver fluke can depress dry matter intake by 10-11%.
“A low-grade infection of just 100 fluke has been shown to reduce milk yield by 400 litres a cow a lacataion and, for a 100-cow herd at 18p/litre, this equates to £7200 a year,” he says.
NADIS also estimate impact on productivity for cattle farming alone costs about £23m a year or £20 per infected animal.
But for dairy herds its not as simple as treating with a flukicide, warns Mr Black. “Milk withdrawal periods are at least seven days and meat withdrawal 56-60 days, so treatment can only really take place during the dry period.”
It is important to remember not all treatments kill all stages of liver fluke, says Mr Cutler. “Farmers should consult their vet as to which product to use, as dose rate is also important,” he adds.
A defined preventative strategy is critical in reducing animal’s exposure to fluke, he says. “Fencing off grazing areas next to water and also maintaining gateways can help. Spreading copper sulphate can also help kill the snail although this may not be so environmental sound.”
Mr Cutler also recommends producers buying in sheep to ask for the liver fluke history on farm of origin and treatment history.