Cattle farmers are being encouraged to vaccinate their animals before turnout, amid growing concerns that routine wormer treatments are no longer reliable.
There is increasing unpredictability of infections and rising concerns about anthelmintic resistance, according to vet Ben Strugnell, from Farm Post Mortems.
He has reported an increase in lungworm cases, even in cattle treated with wormers, suggesting resistance is becoming more prevalent.
“Lungworm thrives in warm, wet conditions, but its timing is unpredictable, making it difficult to target worming treatments effectively,” said Mr Strugnell.
“This often leads to unnecessary treatments, and the use of anthelmintics in this way may be adding to the resistance pressure,” he said.
Mr Strugnell described a case last year where a farmer treated heifers for lungworm with macrocyclic lactones, at housing, but post-mortem results 6-8 weeks later showed high levels of lungworm still present in the lungs, suggesting treatment failure.
The farmer has now opted for pre-turnout vaccination to avoid losses, with Mr Strugnell believing these cases are the tip of the iceberg.
He says vaccination against lungworm in breeding stock pre-turnout should be seen as the gold standard in disease management policy moving forward.
“It’s difficult to predict when lungworm may strike, so vaccinating cattle before turnout allows animals to develop immunity without relying on wormers.”
Recent research from the University of Glasgow adds to the growing evidence of resistance to macrocyclic lactones (MLs), such as ivermectin and moxidectin, where MLs fail to treat lungworm infection in cattle.
The study found that in a group of first season grazing heifers on a Scottish farm, both ivermectin and moxidectin treatments failed to treat the disease.
Clinical signs progressed, and significant numbers of lungworm were observed after treatment, which is highly suggestive of resistance.
“There’s no field test for resistance, so it’s only detected after complete treatment failure,” said study author Paul Campbell, stressing the need for sustainable control measures like vaccination.
He said: “Due to lungworm’s unpredictable nature, vaccination allows cattle to develop reliable immunity while exposed to some lungworm on pasture, reducing the need for wormer treatment, which provides only temporary protection.
"No new wormers are coming soon, so we need to maintain the efficacy of our current products.”
Data indicates lungworm cases are on the rise, with a 10-fold increase in infections since the mid-1990s – particularly in Scotland and northern England.
Between the 2018 and 2019 grazing seasons, cases diagnosed and reported to the GB Veterinary Investigations Diagnosis Network were up by 44% throughout the entire UK.
Lungworm infections occur when cattle ingest grass contaminated with larvae from the parasite Dictyocaulus viviparus. The larvae migrate to the lungs, where they mature and reproduce.
The cycle can repeat rapidly as the larvae are passed out in faeces and consumed by grazing cattle.
