With lungworm cases on the rise, Farmers Guardian explores the disease control options.
Since the mid-1990s, lungworm cases have increased ten-fold, with a change in climate and management practices turning the traditionally youngstock disease into a serious threat for adult cattle.
Vet Andre Baptista, from Westpoint Farm Vets, Chelmsford, says: “While the small lungworm parasite may seem quite insignificant, it is capable of incredible damage and UK farmers grazing cattle should never underestimate it."
Even conservative estimates by researchers at the University of Liverpool suggest a lungworm outbreak will cost £140 per infected cow and the disease is capable of dropping milk production by 4kg per cow per day.
While milk losses make up 50 per cent of infection costs estimates, laboratory fees, treatment expenses, fertility issues and death account for the remaining associated costs.
“While a change in climate and increased diagnostics may have contributed to the increase of lungworm cases we have seen in not only my practice, but also across the country, we can also draw a correlation with producers relying more on long-lasting anthelmintics,” Mr Baptista says.
Here Mr Baptista weighs up the pros and cons of the most common lungworm control practices...
Long-lasting anthelmintics, better known as wormers, expel parasitic worms from the host.
While they are designed to serve as a treatment for infected animals, their short-lived protection window and low price have led producers to rely on them as prevention tools in recent years.
However, cattle need exposure to lungworm to build up immunity, but most anthelmintics prevent this ability, leaving cattle vulnerable as soon as the protection window closes towards the end of the grazing season.
Using a pour on: A liquid wormer is applied topically to the animal, which is then absorbed through the skin from a dosage based on weight.
“It is important to actually weigh the animal prior to administration. On many occasions, I have had clients administer it by estimating the weight and then end up under dosing,” explains Mr Baptista.
“This leads to ineffective treatment and can leave the animal completely vulnerable to lungworm infection.”
Issues can also occur with haphazard administration, with rushed applications resulting in poor dosing and cattle even being missed.
Protection length: 28-45 days depending on product.
Withdrawal period: 15-35 days for meat depending on product.
While some pour-on wormers are licensed for lactating dairy cattle, others are not for use on pregnant dairy heifers 60 days prior to calving, or for lactating animals producing milk for human consumption.
Using an injectable: A liquid wormer is injected into the animal and dosage is based on weight.
“This is an accurate way to administer treatment, but cattle must be weighed to establish the correct dosage,” says Mr Baptista.
Protection length: 14-35 days depending on product
Withdrawal period: 49-108 days for meat, depending on product.
While some injectable wormers are licensed for lactating dairy cattle, others have a withdrawal period up to 80 days on milk being produced for human consumption.
Administering a bolus: A bolus is inserted orally into the rumen to slowly release pulses of wormer treatment for extended lungworm protection.
“Boluses are difficult to use because an animal must be properly restrained for successful administration. There is a lot of room for error, which could result in a wasted treatment and leave the animal vulnerable to lungworm,” explains Mr Baptista.
“Boluses also carry the longest withdrawal periods, ranging from six to eight months on animals for meat, depending on the product used, and even up to eight months for milk produced for human consumption.”
Protection length: 15-21 weeks depending on product
Withdrawal: Six to eight months for meat and up to eight months for milk for human consumption.
Critical take-home points on anthelmintics: Due to concerns over resistance to some types of anthelmintics, Mr Baptista stresses the importance of utilising them on a case-by-case basis only to protect incoming animals to a herd prior to being vaccinated the next grazing season.
“We have to safeguard the products we have now so we can continue to treat sick animals when needed,” he says.
“And due to cattle not building immunity to lungworm while being treated with anthelmintic, producers are taking a huge gamble on their herd’s health and productivity by relying on products with major administration challenges and short protection periods.”
Irradiated larvae are administered orally via a live vaccine to cattle eight weeks of age or older in two doses four weeks apart two weeks prior to turnout.
Because larvae are irradiated, they cannot fully develop, allowing the cow’s immune system to kill off the larvae and the animal to develop immunity.
Protection length: Full grazing season
Withdrawal period: None
Critical take-home points on vaccination: Due to the first vaccination not being suitable for calves under eight weeks of age, producers will have to factor in calf age to their turnout dates.
Cattle must be exposed to lungworm after turnout to develop immunity, which will last throughout the grazing season.
It is also advised to work with a veterinarian to develop a complementary gut worm control protocol as some gut worm products can prohibit the development of lungworm immunity.
Mr Baptista says: In order for cattle to build and maintain immunity, they must have exposure to lungworm. One outbreak of lungworm in a dairy or beef herd can cause severe long-lasting impacts in depressed milk production, daily liveweight gain and multiple secondary issues.
"Because constant exposure is so critical, and the damages of lungworm are so high, I advise most of my clients to not only use vaccination as their lungworm control, but to revaccinate animals in case pasture is not contaminated enough to ensure immunity.
“Ultimately, however, I advise all producers to work closely with their vet to adequately weigh the pros and cons associated with each lungworm control option to find the one that best suits their herd.”