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lungworm lifecycle

Lungworm in Cattle – is worming your only option?

Sylvaine Lacrosse BVetMed MRCVS Molecare Farm Vets

When discussing lungworm (Dictyocaulus viviparus) control with farmers, the majority will have a summer worming plan in place. Whilst worming can be an important part of the prevention and control of this parasite, this needs to be targeted and other preventative tools such as vaccination could also be beneficial. In order to identify the best approach for your farm, you need to understand the lungworm risk factors and how these could impact your herd.

A life-cycle recap

NL July lungworm in cattle
Picture courtesy of COWS.org.uk

Why worry about lungworm?

The biggest concern from a veterinary perspective is that lungworm can put a considerable burden on the animal, and leave your cattle struggling for breath and with obstructions to their airways.

An animal with lungworm will be in respiratory distress until treatment works, however the effectiveness of treatment is not always guaranteed and so prevention is always better than cure.

Additionally, an animal showing clinical signs is often the tip of the iceberg, and so there is always a chance that multiple animals are affected in the herd. A lungworm outbreak has been conservatively estimated at £140/ adult cow in a milking herd (Holzhauer and others 2011) due to reduced growth rates, dropped milk yield, deaths, treatments and general loss of production.

Which animals are most at risk?

Outbreaks are most commonly seen when naïve animals with no immunity are exposed to the parasite for the first time. Lungworm larvae can overwinter on pasture and in carrier cattle, continuing the life cycle each year. Cattle can therefore pick up infection as soon as they are turned out in spring, and this can build up to clinical disease from June onwards.

Long-acting wormers can also put animals at risk later in their lives as this prevents young animals from building up a natural immunity to the parasite. For example, replacement heifers wormed in their first and second grazing seasons may not have been exposed to lungworm until they enter the main herd, when they are then put out to grass, the risk of a disease outbreak is very high.

How will I know if my cattle are affected with lungworm?

Picture courtesy of MSD Animal Health


Despite being widely underused, vaccination should be the first line of defense before calves get turned out. Once exposed to the worms at pasture, the calves can then develop immunity to the adult worms. The vaccine allows a small number of lungworm from natural infection to complete their life-cycle, meaning there is a continued development of natural immunity throughout the grazing season. In comparison, over-reliance and overuse of wormers does not allow this natural immune response to occur which can be important for later life.

In order to develop an all-encompassing lungworm control plan, farmers should work with their local farm vet. Creating a health plan, as we do at Molecare, is a great opportunity to work out a risk-based approach for tackling the disease with the aim to reduce the overall cost of this parasite on farm from both a welfare and financial perspective.

If you would like any advice on any of the above contact the practice on 01392 872934 or email [email protected]

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