Herd of black and white cows in pasture

Curb anthelmintic resistance in cattle

There are approximately 20 different species of gutworms that live in the intestines of cattle and cause a condition called parasitic gastroenteritis (PGE).

Ostertagia and Cooperia are the most economically important species causing significant threat to profits on farm and in both these species resistance to anthelmintics has been detected.

Classic symptoms of PGE in young animals are diarrhoea, reduced feed intake which impacts growth rates and a rapid drop in condition. However, the more sinister effects are those that are subclinical, meaning the signs are not always obvious.

PGE, caused by uncontrolled worm infections, has significant negative economic effects causing poor production and a subsequent loss of profitability. Although young cattle are usually the focus of worm control, adult cattle should not be overlooked as they can be a source of environmental contamination and can also experience production loss.

COWS (Control Of Worms Sustainably) is a valuable resource for UK farmers and can be

accessed at cattleparasites.org.uk.

COWS’ top tips for controlling cattle roundworms are:

1. Identify Risk

• All cattle on pasture are at risk with young animals being at most risk of PGE 

• Permanent pastures grazed by youngstock in the previous 6 months are a high risk

• Time of year with mid-summer onwards carrying higher risk

• Young cattle not treated with an anthelmintic at housing are at high risk in late winter

2. Treat Appropriately

• Utilise targeted treatment (either individual animals or groups of animals) at the appropriate times. Specific diagnostic tests including FECs and growth rates will help identify cattle that require treatment.

• Strategic use of wormers

• Effective treatment at the time of housing

3. Avoid Resistance

• Follow label instructions of anthelmintics correctly

• Avoid treating cattle unnecessarily 

Faecal Egg Counts are a valuable tool for effective worm control. A Faecal Egg Count (FEC) test will indicate when a treatment is required for a herd or group of animals.

One of the common methods of worming animals is a blind worming programme without knowing the status of the herd or

group. Very often a herd would receive treatment when it is not required resulting in not only unnecessary costs but also increased likelihood of resistance because low numbers of worms will be exposed to the drug.

Knowing the FEC status of the herd at various times of the year will guide the worming protocol customised for each farm by your vet or RAMA (Registered Animals Medicines Advisor).

Faecal egg count tests can also be used to measure anthelmintic resistance in your herd. The use of Faecal Egg Count Reduction testing (FECRT) is critical in assessing the effectiveness of the wormer being used. It uses a pre-treatment FEC and a post-treatment FEC (interval dependent on the type of wormer being used) and the percentage reduction in eggs shed is then used to determine how effective a particular class of wormer is.

In other words, it will give an indication if there is anthelmintic resistance or not. This is vital as blind treatment with a product that has resistance to it will increase the resistance problem and will not reduce the worm burden meaning economic losses will continue.