PREVENT – Parasite management options

There are several things you can do as a livestock owner to reduce the parasite risk to your livestock.

All the following recommendations should be taken into consideration with your specific farm situation and in collaboration with your vet/SQP. It is not a ‘one size fits all’ scenario! Suddenly halting all use of parasite treatments can compromise the health and welfare of your livestock. Any parasite control strategy should be integrated as part of your health plan.

Breed your own replacements

This reduces the risk of bringing new parasites onto your farm and homebred replacement stock are more likely to have resistance to parasites present on your farm. It may be possible to breed genetically resistant livestock to high parasite burdens.

Quarantine treatments

It is important if you are buying in stock that you quarantine and effectively kill all parasites in these bought-in animals before they join your herd/flock. Bought-in animals can bring parasites such as liver fluke and lungworm which may not already be present on your farm, not to mention infectious diseases. Speak to your vet / SQP about effective quarantine testing and / or treatment for your herd / flock.

It is possible to ‘buy-in’ resistant worms / fluke which can be released onto pasture. By using multiple treatments during your quarantine period – you can reduce the risk of this occurring. This requires a FECRT Faecal Egg Count Reduction Test to confirm efficacy. Please do speak with your vet.

The quarantine period can be an important time to test your animals for other infectious diseases that can be brought onto your farm and quarantine is an important biosecurity procedure to protect your farm and your other livestock from disease.

Healthy livestock

We know that strong host immunity is important in disease control – and disease caused by parasitic worms is no different.

Ensuring youngstock have had the best start in life with adequate colostral transfer will help as it gives livestock the best start in life and reduces the risk of disease early in life. This can be easily monitored. Speak to your vet for more information.

Young animals have little to no immunity to gutworms and so are the most vulnerable to infection. This also makes them a good “host” for the parasites. They also have larger volumes of eggs in their faeces. We say youngstock act as ‘multipliers’ and this is important when we come to assessing pasture ‘risk’ as a prevention strategy.

A mature animal (over 3years old, that has grazed annually) should not need to be treated for gutworms under normal circumstances as they will have built up some resilience to them.

Fluke is a bit different as animals do not build resistance to it. It is thought that there may be a genetic resistance to liver fluke and by breeding those animals that are more resistant, you can increase your herd / flock resilience to the damaging effects of liver fluke. ICBF (Irish Cattle Breeding Federation) have listed bulls on their database based on liver results coming back from abattoirs. This resource available in Ireland may be a starting point to breeding Liver fluke resistance into a herd of cows.


Nutrition also plays a role in host immunity with animals on a higher plane of nutrition often performing better. Studies have shown that ewes on a high protein diet have lower FWECs than those on a standard protein level.

What is their mineral / trace element status? Have they received a bolus if it is required or receiving another mineral supplementation?

Lungworm control

Lungworm vaccination can mean the difference between having to use a worming treatment or not.

It is most often used in first or second-year grazing animals. It can also be used as a lungworm control option for adult animals in flying herds. It should only be used if lungworm has been diagnosed on your farm. Please speak to your vet / SQP about options.

Vaccination will promote immunity, but timing is important. The vaccine itself has a short shelf-life so should only be ordered when required. Administering it can be quite time consuming as it requires two doses several weeks apart and both doses should be completed well before turnout, so some planning is required.

Animals will retain immunity if they are grazed and ‘exposed’ to lungworm each season. This can be difficult to achieve in milking herds where dry cows, as an example, may miss a grazing season as the milking herd are housed. It is important that good records are kept, and these animals are monitored for any clinical signs.


Vaccination can also be used to boost immunity – animals suffering from concurrent disease / immunosuppression are more at risk of becoming clinically diseased from high parasite burdens on pasture.

Natural antiparasitics

Incorporating other grasses / herbs into your pasture. Plants such as chicory has been shown to lead to a 40% reduction in worm burdens in sheep. Plantain may also have an effect. Other plants that have been studied include Sainfoin and birdsfoot trefoil as they contain condensed tannins which disrupt the parasite lifecycle.

Longer sward length

Longer sward length of grasses may be another tool in the box for controlling parasite burden in your animals. Worm eggs tend to be found at the base of grass stalks, so if cattle or sheep are grazing longer swards, it may be possible to reduce contact with worm eggs which cause infection by digestion!