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Lungworm the background (video 1 of 4)



Over the next couple of days, I’m going to look at lungworm in more detail. In four written articles and videos, digging deeper into what has become a real problem on some dairy farms.

For farms that don’t have issues with lungworm, this series should be about understanding the principles of control in the future.

Over the last number of year’s, there has been a spike in the number of dairy farms in particular where lungworm has become a big issue. It is not just dairy farms but also some dairy to beef units and suckler farms.

Even flocks can have issues with lungworm.

Dictyocaulus viviparous is the parasite we often refer to as lungworm (hoose). It is a roundworm that causes its clinical signs and pathology in the lungs of ruminants.

This parasite will develop into adult lungworm which resides in the bigger airways. This occurs by larvae moving through the lung tissue as they develop.

In big numbers, this can cause a lot of damage. The most obvious signs with lungworm can be coughing. Some farms I have been on though don’t always see this coughing, we should never make presumptions about any disease.

Lungworms also can depress immunity and open the door to other viruses and bacteria. In adult dairy cows it has been estimated to cost €150 per clinical case.

Most dairy farmers will tell you the lift in milk yield following worm dosing can be significant. The problem is some farms are now using multiple doses during the grazing season. This is not sustainable and we must look at new ways to control the disease on these farms.

So why is lungworm more of an issue now?

Unfortunately for us in Ireland, the conditions often required for grass growth can be the same ones that parasites like. For them to reproduce and spread, they like moisture and mild weather. This can be helped where stocking rates go up at pasture.

This allows them (larvae young lungworm) to move from dung onto the grass to be ingested. There is little we can do about the weather, but we can react to when conditions are right for larvae and certainly be more vigilant.

Lungworm can be unpredictable meaning that when we are using dosing (wormers) we need to understand when is the best time. Currently, we react to symptoms around lungworm treatments meaning we have the risk of damage being done. In later videos and articles, I will talk about control programs and building the animal’s immunity. For me, this is about taking back some of the unpredictability.

One area I am interested in with all parasites is the potential mixed species swards may have. They will not be a panacea, but on farms and some research indicates they seem to reduce parasite burdens. This is probably related to higher grazing heights (cleanouts) and physical difficulty parasite larvae may have to climb them. Some are also said to contain natural tannins which may play a role in slowing down parasite development.

More research is needed in this area. As part of grazing systems, we must also look at rotations and where first grazers, in particular, will be. With some farms that use contract rearing, this can also be a challenge. Where in some cases they receive little exposure until their return to the grazing platform.

With the growing challenge of anthelmintic resistance, we must take a more proactive approach to understanding and controlling lungworm on problem farms.

Mild winters also present a challenge to parasite controls. There is some evidence if it’s not too cold that larvae will survive over winter on pasture. While these numbers may be small, it can lead into the start of another breeding cycle for the parasites. The main source from grazing season to grazing season is thought to be carrier animals with lungworm larvae in their lungs.

Finally, we need to be more proactive around how we use anthelmintics on our farms. With no new products and the threat of resistance growing. We need to treat them as precious resources. With first graders, we must also adopt the use of more diagnostics. We need to start building proactive animal health plans that involve strategic plans around parasite controls.

The overuse of wormers can create issues with lungworm, where natural immunity in older animals doesn’t develop properly.


So we certainly have some challenges around parasite controls and in some farms lungworm control.

With a little more planning and a clear understanding of lifecycles and risk, we can take action.

The next article will cover the lifecycle of the lungworm parasite.

Happy safe farming

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