Cases and resistance against wormers continue to rise.

Cattle farmers are being urged to consider vaccinating their herds against lungworm before turnout, as cases continue to rise.

The advice comes after further research found that lungworm is continuing to develop resistance to commonly used wormers.

The study, from the University of Glasgow, saw evidence that lungworm was becoming more resistant to macrocyclic lactones (MLs) such as ivermectin and moxidectin. Data suggests that these drugs had failed to control lungworm infections amongst cattle.

Cattle become infested with lungworm when they graze pasture contaminated with larvae from Dictyocaulus viviparus. Ingested larvae will migrate to the lungs where it matures, reproduces and releases eggs.

These eggs are then coughed up, swallowed, and excreted, recontaminating the grazing environment.

Dr Kat Baxter-Smith, veterinary advisor with MSD Animal Health, says that vaccinations are key for controlling lungworm, enabling animals to build immunity. However, she says that pre-turnout vaccination has never been more important. 

The study reveals that lungworm has increased 10x by the mid-1990s. Between 2018 and 2024, diagnosed cases of parasitic pneumonia rose by 100 per cent across the UK.

Anecdotal reports and governmental data has also suggested that lungworm could be active in adult cattle, rather than just first- or second-season grazers.

Adult cattle can develop clinical diseases later in the season, often due to a lack of immunity. This lack of immunity is often the result of natural challenge, immunosuppression from other disease or very high worm burdens.

This makes it particularly important they are protected through vaccination.

Dr Baxter-Smith warns that routinely using wormers will encourage resistance to them. Meanwhile, vaccination will lead to immunity by providing controlled exposure to irradiated larvae.

Dr Baxter-Smith said: “Every farm is different. Talk to your vet about your grazing system, the age of animals at risk, and the worming policy you use,

“A vaccination plan tailored to your farm can help safeguard herd health, reduce financial losses, and protect the efficacy of the wormers we still have.”

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