Lungworm vaccine cuts wormer use by nearly 90%, study shows

Vaccinating youngstock for lungworm has resulted in an 87% reduction in the use of macrocyclic lactone wormers among dairy farmers who took part in a Welsh study.

The trial was led by Carmarthen-based vet Anuschka Marsman of ProStock Vets, who was supported at the start of the study by fellow vet Rob Howe.

It set out to shed light on how vaccinating for the parasitic infection could reduce routine wormer treatments, and the subsequent benefits of that to dung beetle populations.

See also: Why you should stop blanket cattle worming and how to do it

Lungworm disease, which is more commonly seen in first-year grazing animals in summer or early autumn, is one of the most significant respiratory diseases of cattle.

It can be very damaging economically and is also of major welfare concern. However, vaccination can protect animals from infection.

A total of 31 farmers, all First Milk suppliers in south and west Wales, took part in the study, which ran between March and December 2024; of these, 15 opted to vaccinate – three were already doing so.

Worm tests

Pooled samples for faecal egg counts (FECs) were collected monthly by the trial farms.

These were analysed for gastrointestinal worm eggs using Fecpak, a tool for parasite diagnostics and decision support that enables simple FECs to be taken on-farm without a microscope.

On farms where the FEC result was greater than zero, another sample was taken two weeks later to establish if the animals needed to be wormed.

Cattle condition and signs of coughing were also factored into that decision-making process.

Testing for fluke antibodies and adult lungworm antibodies was carried out soon after the first-year grazers were housed in autumn 2024.

Levels of serum pepsinogen in the blood were also assessed, as these are elevated when there is a high gastrointestinal worm burden.

For the milking herd, bulk milk was analysed for adult lungworm antibodies and fluke antibodies.

Anuschka Marsman © Debbie James

Results

All farms tested negative for lungworm antibodies in bulk milk, while two-thirds were positive for fluke. For adult cows, the FEC readings were at zero or very low levels, so no dosing was required.

Anuschka says using the lungworm vaccine in youngstock to build up immunity was clearly shown to reduce anthelmintics use on the trial farms.

“There has been an 87% reduction in the incidence of worming with ML [macrocyclic lactone] – group 3 wormers – on the farms that used the lungworm vaccine,” she reports.

Another benefit of vaccination is that when cattle do not contract clinical lungworm infection, there is no permanent damage to their lungs or an impaired growth rate.

Across all 31 farms, with FEC sampling and blood testing used to inform worming decisions, there was a 65% reduction in use of ML wormers.

“Far fewer farmers applied wormers before or at turnout, and most were guided by FECs during the grazing season as to whether to worm or not,” says Anuschka.

The farmers were asked to take note of the sward length when cattle were turned in to pasture and when they were exiting it.

Most nematode eggs harbour in the bottom 10cm of the sward where conditions are moist and the temperature is more favourable for them.

The farmers were also encouraged to assess the pasture risk for first grazers, ideally turning them onto silage aftermaths or reseeded pasture.

Heifers on 10 of the 16 farms that chose not to vaccinate showed signs of exposure to lungworm in their first grazing season.

Cost benefit

The study also looked at the economics of lungworm vaccination, and these were favourable, says Anuschka.

She calculates that in a 200-cow dairy herd with 100 heifer replacements worming would cost £3,937

This would be in a herd that opted for routine worming (instead of vaccination and monitoring of FECs).

It also factors in the labour cost associated with worming the first grazers three times and the second grazers twice.

That calculation takes into account future performance losses resulting from lung damage, costed at £50 a head across an estimated 50 first grazers.

If that same farm vaccinated and monitored FECs instead of routine worming, the cost would be £1,710.

In addition, the economic consequences of heifers suffering damaged lungs from contracting the disease would be avoided.

The effect on dung beetles

© Adobe Stock

Youngstock need to build up immunity to parasitic nematodes when they are at grass.

This requires about eight months of exposure to them. “Using as little anthelmintics as possible, and as much as necessary, is of vital importance to ensure exposure criteria are met,” says Anuschka.

Her study, funded by Farming Connect and supported by First Milk, also looked at populations of dung beetles on the 31 farms taking part.

These insects are considered crucial for improving soil structure, as well as reducing parasite burdens in livestock and nuisance fly populations.

They also play an important role in breaking down dung pats in fields – without this, farmers would lose 16% of their grazing area, Anuschka points out.

“It has been estimated that dung beetles save the UK cattle industry £367m/year through the provision of ecosystem services,” she says.

She adds that about half of the 60 different species of dung beetle in the UK are considered scarce or listed as under threat.

The highest scores of dung beetles were found on the farms that had used the least amount of anthelmintics in the year prior to the study; none of these had treated their adult cows for worms.

Yet the top dung beetle score in the project was only 50, which is considered “moderate”.

By comparison, a score of more than 80 is deemed to be “very healthy”, according to the information hub Dung Beetles For Farmers.

Choice of wormer

Dung beetle populations will take years to recover, as many species only reproduce once or twice a year, says Anuschka.

However, less reliance on anthelmintics, and a more responsible approach to their use, will have a positive effect.

And because anthelmintics vary in their toxicity to dung beetles, using those that are less toxic to them would make a significant difference.

“Group 3 wormers – MLs, avermectins and milbemycins – are considered the most detrimental to dung beetles, and the continuous-release, long-acting formulations of doramectin are especially detrimental,” says Anuschka.

Other measures, such as leaving some healthy-looking animals untreated, are important if dung beetles are to survive, she adds.

“Farms could also have a couple of cattle grazing for 12 months of the year to ensure that the dung beetles survive in sufficient numbers throughout the winter, as this allows fresh dung to be available year-round.”

Introducing different dung beetle species on farms and providing a range of habitats would also help, Anuschka suggests.

In addition, she urges farmers to use parasitic wasps instead of synthetic pyrethroids for managing fly populations wherever possible.

“If we look after dung beetles, then we will have more phoretic mites, which will also help to control flies,” she says.