top of page

Plan now to remove ‘unwanted guests’ (Oct 2021)

Pre-housing parasite control can pay dividends when it comes to preventing health and welfare issues during the winter months. We spoke to Boehringer Ingelheim vet Sioned Timothy to find out more.


As herds are housed for winter, producers should also be thinking about any ‘unwelcome friends’ they may be bringing in with them. Parasites, both internal and external, not only impact cow welfare but can also compromise herd health, fertility and productivity.

“Having plans to control parasites at housing is vital to ensure cows and heifers are treated in a timely and effective way,” says Boehringer Ingelheim Animal Health’s vet Sioned Timothy.

These ‘visitors’ include mites and lice, gut worms, lung worm and liver fluke. “There are a lot of parasites to consider. So planning is important to ensure all potential problems are tackled at the correct time, and with a targeted and effective product.”

A check list is a good starting point – producers will know the parasites present on their farm and in their herd. It’s then a case of developing a monitoring and treatment schedule, to make sure animals are treated at the optimal time to ensure best control of each parasite. “The purpose of pre-housing treatments is to remove or clear any internal parasite burdens, which may have been established during the summer and autumn grazing season,” says Ms Timothy. “These can all impact productivity.”

Quickly multiply

Ectoparasites, which live on the skin, include mites, which cause mange, and biting and sucking lice, which cause itching and irritation. And if they’re not tackled they will thrive and quickly multiply during housing, when cows and heifers are in close proximity and in warmer conditions. “Cattle should, ideally, enter housing free of mites and lice. If cattle take ‘uninvited guests’ into housing, mites and lice populations can ‘explode’ and they’re then more difficult – and more costly – to control.”

Herd Health: planning is key to tackling parasites prior to housing

Ms Timothy says while it’s not typically possible to detect the low-level infections that may be present at housing, consideration should be given to whether a treatment against external parasites is warranted based on farm level risk and disease history. If required, an appropriate treatment can be administered to all animals within the group at housing.

Endoparasites, which live in the tissues and organs of cattle, include gut worm, liver fluke and lung worm. The former will be present in grazing cattle and numbers will build – both on pasture and in livestock – as the summer and autumn progresses. “Gut worm exposure will be high in most herds by autumn,” says Ms Timothy.

Gut-worm ‘tolerance’

She says adult cows do develop a degree of immunity or ‘tolerance’ to gut worm. “But studies have highlighted that worms impact production. A simple bulk milk test to measure antibodies can assess the level of exposure cows have had at grass. This, together with treatment history, can help determine whether a housing treatment is appropriate.”

Young stock, on the other hand, haven’t developed immunity so effective worm control is important during their first and second grazing seasons. “Keep a close eye on heifers – monitor growth rates and talk to your vet about a suitable and effective parasite control programme.

“And a treatment at housing is recommended to remove worm burdens acquired during the grazing period, and to maximise health and productivity. A product effective against the encysted stages of the gut worm Ostertagia ostertagi should be used to prevent type II ostertagiosis – winter scours – in heifer calves,” stresses Ms Timothy. “Although rare, this is potentially extremely serious and can result in severe growth and performance checks, as well as fatalities.” This condition is caused by dormant worms maturing in the heifer’s gut. “When outbreaks occur a small proportion of young stock will typically be affected, often around 20% of a group. But a high percentage of cases will be fatal.

“The worms cause significant tissue damage to the abomasum as they emerge. Where heifers do recover it’s a long process and they rarely reach their true potential.” Both the clinical and sub-clinical effects of gut worm can impact heifer performance, resulting in an estimated delay of 10 days to puberty and a reduction of 331kg in first-lactation milk yield.

Producers should also talk to their vet about liver fluke. “Many producers know if this is a problem on their unit and in their herd. But it’s much more widespread today and not just confined to the wetter areas of the UK.” Like gut worm, testing a bulk milk sample for antibodies can determine whether cows have been exposed to this parasite, and inform treatment decisions and protocols. “Treatment often takes place at drying off because there are no anthelmintics available that offer zero-milk-withhold. So test and monitor your herd and, working with your vet, decide on a treatment protocol for liver fluke and add it to your wider parasite control plans,” add Ms Timothy.

Controlling liver fluke in young stock begins with getting to grips with farm status and, again, testing and talking to your vet or SQP. “We’re looking to prevent growth checks associated with subclinical disease and, where infection is present, treatment at housing is recommended. It’s also important to put steps in place, such as follow up diagnostic testing, to ensure cattle are turned out free of a fluke burden because it breaks the liver fluke’s life cycle.

“Blood testing can be used to assess whether young stock have been exposed, and faecal sampling can determine whether cattle are carrying an adult liver fluke burden. But speak to your vet about an appropriate testing strategy.”

Controlling liver fluke in young cattle can reap significant rewards in young stock and milking cows. The growth reductions associated with a liver fluke challenge are estimated to delay puberty by 25 days and decrease first-lactation milk yields by 159kg.

Lung-worm concern

Ms Timothy is particularly concerned about lung worm this year. “Case numbers are reportedly high this year, probably due to the warm and damp weather. Vigilance is key here. Keep a close eye for coughing cows. Lung worm should always be suspected in cattle coughing at grass. “Not all cows with lung worm will show symptoms, but coughing cows are your cue to investigate further and find out whether lungworm may be the cause. If cattle are housed with a lungworm burden this can increase the risk of respiratory disease associated with secondary infections.”

Again, lung worm will compromise milk yield, with infections associated with average daily yield reductions of 1.6kg in cows.

“So if you suspect lung worm, talk to your vet and/ or SQP, and take advice on diagnosis and treatment,” she says, adding that there are zero-milk-withhold treatments available.

Ms Timothy stresses that, when developing a plan for parasite control at housing, diagnostic testing and selecting the correct product and treating at the right time are all essential. “Not only to ensure effective parasite control and minimise the risk of resistance, but also to ensure the best return on investment.”

For more information and guidance on cattle worming best practice visit the COWS website at:

14 views0 comments


bottom of page