Responsible and sustainable use of parasiticides

Using medicines responsibly ensures products are only used when necessary, ideally supported by a diagnosis or a risk assessment.

Choosing the right product and getting the most from it are key to ensuring optimum livestock performance for the least cost while reducing the risk of drug resistance.

Our parasite control guide provides an accurate, easy-to-use reference on all available parasiticide products in their various chemical groups and summarises the parasites they have been licensed to treat.

Coccidiocides are not currently included in the booklet. Decisions on the choice of product should be discussed with your vet, suitably qualified person (SQP) or registered animal medicines adviser (RAMA).

Many compounds used to treat parasites can negatively impact invertebrates such as dung beetles, flies and aquatic fauna.

This can occur when the active ingredients or their metabolites are excreted from treated animals or when ingredients leach into the environment.

Avoiding unnecessary treatments minimises environmental risks. Treatment decisions should form part of an integrated approach to parasite management.

To minimise environmental risk, products should be:

• Used only when there’s genuine risk to animal health and welfare
• Supported by diagnostic testing, clinical signs and forecasting information
• Stored in the right conditions
• Selected and applied correctly, following manufacturer guidelines
• Tested post-treatment to help avoid future ineffective product selection
• Disposed of responsibly, including packaging, following manufacturer guidelines and local guidance on any precautions

The activity of a medicine within the animal and the environment are not the same thing. The meat/milk withdrawal period of a product has no direct relationship to the risk to the environment.

Tests to detect and diagnose parasitic infections form a vital part of responsible parasite control and treatment.

A faecal egg count (FEC) provides information about the number of worm eggs present in faeces and is an indication of the number of adult worms present in the animal.

It's a useful management tool that can determine timing of any need to treat, test treatment effectiveness and estimate the amount of contamination going onto the pasture.

To get a reliable and representative result, collect fresh faecal samples from 10–15 animals within a mob that are representative of the group.

The interpretation of a faecal egg count is crucial – what does the result mean in terms of treatment and/or next steps?

FECs should not be used as a diagnostic tool, and several other factors should be considered:

• Animal performance and condition
• Health factors
• Age of the animals
• Previous treatments

Knowing which parasites are contributing to the FEC may require additional laboratory testing.

For example, in sheep, a high strongyle count may suggest the presence of haemonchus, but this can only be validated using a laboratory speciation test.

Ideally, FECs should be carried out every 2–4 weeks during the grazing season.

Alternatives to FEC include ELISA-based tests, which can detect either the immune response of an infected animal or the presence of parasite antigens.

These methods are carried out on blood, milk (individual or bulk milk), faeces or saliva samples.

A new lateral flow test (similar to Covid testing) for liver fluke can be used to monitor exposure in first-season grazing animals. Skin scrapes and post-mortems also offer valuable insight.

If you suspect that a product has not been effective, or has resulted in adverse symptoms or reactions, this information must be reported to the relevant authorities.

Anthelmintics (wormers) are used to treat and prevent parasite infections caused by roundworm, tapeworm, lungworm and liver fluke.

These products fall into the following groups:

• Group 1: Benzimidazoles (BZ) (White)
• Group 2: Levamisole (LV) (Yellow)
• Group 3: Macrocyclic lactones (ML) (Clear)
• Group 4: Amino acetonitrile derivatives (AD) (Orange)
• Group 5: Spiroindoles (SI) available as a multi-active (Purple)

Anthelmintics belonging to these groups are active against the major species of gut roundworms and lungworms.

Some will also have activity against liver fluke and tapeworms. ML (Group 3) injectables and pour-ons also have activity against some ectoparasites.

Other products are more specific in the parasites they will kill, i.e. narrow spectrum. Most anthelmintics in this category are active against liver fluke or ectoparasites.

Choosing the most appropriate product for the parasites present is vital.

Targeting the right parasite will give predictable results and may mean retreatment is less likely to be needed. This may also reduce unnecessary selection pressure for drug resistance.

When using any medicine or vaccine, always read the product label and package insert so you understand how it needs to be administered to the animal.

If you don’t understand something or need further information, ask your vet or SQP/RAMA.

• Choose the most appropriate product for the parasites you need to treat
• Store wormers according to instructions, usually away from direct sunlight and extreme temperatures
• Always read the product label to check it’s suitable for the livestock you want to treat
• Make sure the dosing equipment is clean, measuring accurately and suitable for the product
• Follow the manufacturer’s instructions carefully, paying particular attention to specific methods for ear injections and intraruminal (rumen) boluses
• Dose according to liveweight. Weigh animals for accuracy and split groups if there is a wide weight range
• Keep clear records of the product, batch number, amount used, expiry date, animal identity, treatment dates and withdrawal periods
• Note withdrawal periods for milk and meat and ensure they are adhered to. Withdrawal periods do not relate to the length of activity of a product (this will be shown elsewhere on the label)
• Do not mix wormers together or combine them with other products, as this can inactivate active ingredients

You can find more information in the data sheet or the summary of product characteristics (SPC).

Data sheets can be found on noahcompendium.co.uk and the NOAH Compendium app.

SPCs are available at vmd.defra.gov.uk

If you can’t find the information you need, contact the manufacturer directly.

Do you need to treat?

• Which animals are at risk?
• Have they grazed high-risk pasture?
• Have weather or grazing conditions increased risk, for example wet weather and liver fluke?
• Has the risk been monitored, for example through faecal egg counts (FECs)?
• Could grazing management reduce the risk and need to treat, such as moving lambs or calves to low-risk pasture?

What are the target parasites?

• Choose treatments based on the target parasites, the life-cycle stage, the time of year and objective (curative or preventative). Only use combination products when the target parasites are present

Avoid overuse of the same products

• Consider alternative chemical groups, where possible, to reduce selection for resistance to one group

Withdrawal periods

• Consider withdrawal periods carefully when choosing a product

What pack size is required?

• If a pack size is slightly less than required, leave one or two fit animals undosed
• Never underdose the whole group

Administer effectively

• Make sure you have the right equipment, that it is calibrated and that you know the correct dose rate for the animal’s weight
• Avoid underdosing or overdosing
• Always follow the manufacturer’s recommendations, store products correctly and do not use out-of-date products

• Using medicines responsibly
• Worm control in sheep
• Liver fluke control in grazing livestock